EARTH SCIENCE

Theorists Propose a New Way to Shine And a New Kind of Star: 'Electroweak'

2009-12-15T05:54:00.000-08:00

Dying, for stars, has just gotten more complicated.

For some stellar objects, the final phase before or instead of collapsing into a black hole may be what a group of physicists is calling an electroweak star.

Glenn Starkman, a professor of physics at Case Western Reserve University, together with former graduate students and post-docs De-Chang Dai and Dejan Stojkovic, now at the State University of New York in Buffalo, and Arthur Lue, at MIT's Lincoln Lab, offer a description of the structure of an electroweak star in a paper submitted to Physical Review Letters.

Ordinary stars are powered by the fusion of light nuclei into heavier ones -- such as hydrogen into helium in the center of our sun. Electroweak stars, they theorize, would be powered by the total conversion of quarks -- the particles that make up the proton and neutron building blocks of those nuclei -- into much lighter particles called leptons. These leptons include electrons, but especially elusive -- and nearly massless -- neutrinos.

"This is a process predicted by the well-tested Standard Model of particle physics," Starkman said. At ordinary temperatures it is so incredibly rare that it probably hasn't happened within the visible universe anytime in the last 10 billion years, except perhaps in the core of these electroweak stars and in the laboratories of some advanced alien civilizations, he said.

In their dying days, stars smaller than 2.1 times our sun's mass die and collapse into neutron stars -- objects dense enough that the neutrons and protons push against each other. More massive stars are thought to head toward collapse into a black hole. But at the extreme temperatures and densities that might be reached when a star begins to collapse into a black hole, electroweak conversion of quarks into leptons should proceed at a rapid rate, the scientists say.

The energy generated could halt the collapse, much as the energy generated by nuclear fusion prevents ordinary stars like the Sun from collapsing. In other words, an electroweak star is the possible next step before total collapse into a black hole. If the electroweak burning is efficient, it could consume enough mass to prevent what's left from ever becoming a black hole.

Most of the energy eventually emitted from electroweak stars is in the form of neutrinos, which are hard to detect. A small fraction comes out as light and this is where the electroweak star's signature will likely be found, Starkman, said. But, "To understand that small fraction, we have to understand the star better than we do."

And until they do, it's hard to know how we can tell electroweak stars from other stars.

There's time, however, to learn. The theorists have calculated that this phase of a star's life can last more than 10 million years -- a long time for us, though just an instant in the life of a star.

Portions of Arctic Coastline Eroding, No End in Sight, Says New Study

2009-12-15T05:50:00.000-08:00

The northern coastline of Alaska midway between Point Barrow and Prudhoe Bay is eroding by up to one-third the length of a football field annually because of a "triple whammy" of declining sea ice, warming seawater and increased wave activity, according to new study led by the University of Colorado at Boulder.

The conditions have led to the steady retreat of 30 to 45 feet a year of the 12-foot-high bluffs -- frozen blocks of silt and peat containing 50 to 80 percent ice -- which are toppled into the Beaufort Sea during the summer months by a combination of large waves pounding the shoreline and warm seawater melting the base of the bluffs, said CU-Boulder Associate Professor Robert Anderson, a co-author on the study. Once the blocks have fallen, the coastal seawater melts them in a matter of days, sweeping the silty material out to sea.

Anderson, along with collaborators Cameron Wobus of Stratus Consulting and Irina Overeem of CU's Institute of Arctic and Alpine Research, or INSTAAR, each presented results from components of their study at the annual meeting of the American Geophysical Union in San Francisco held Dec. 14-18.

The problem is caused by several factors, including increased erosion along the Alaskan coastline due to longer ice-free summer conditions and warmer seawater bathing the coast, Anderson said. The third potential factor is that the longer the sea ice is detached from the coastline, the further out to sea the sea-ice edge will be. This open-ocean distance between the sea ice and the shore, known as the "fetch," increases both the energy of waves crashing into the coast and the height to which warm seawater can come into contact with the frozen bluffs, said Anderson.

"What we are seeing now is a triple whammy effect," said Anderson. "Since the summer Arctic sea ice cover continues to decline and Arctic air and sea temperatures continue to rise, we really don't see any prospect for this process ending."

In addition to Wobus and Overeem, co-authors on the studies include Gary Clow and Frank Urban of the U.S. Geological Survey in Lakewood, Colo., and Tim Stanton of the Naval Postgraduate School in Monterey, Calif.

The shoreline bluffs are made up of contiguous, polygon-shaped blocks, primarily made of permafrost and each roughly 70 to 100 feet across, he said. Ice "wedges" created by seeping summer surface water that annually freezes and thaws are driven deeper and deeper into the cracks between individual blocks each year. The blocks closest to the sea are undermined as warm seawater melts their base, and eventually split apart from neighboring blocks and topple during stormy conditions, said Anderson.

The researchers used a variety of instruments and methods in the study to examine the dynamic transition between the land and the sea, including time-lapse photography of shoreline erosion, global positioning systems (GPS), meteorological measurements including temperature and wind speed, and sediment analyses of the coastal bluffs. Offshore measurements included sea-ice distribution, ocean floor depth, sea-surface temperatures and wave dynamics, said Anderson, also a fellow at INSTAAR.

The time-lapse images were taken with four tripod mounted "game cameras" often used by hunters and wildlife biologists and which were set up parallel to the shoreline. The cameras snapped pictures every six hours during the 24-hour summer daylight months to track the effects of the waves on the coastline, said Anderson.

"Once one of these blocks topples, the process continues on to the next block," Anderson said. "These images are very powerful, because they pick up activity during severe storms when we aren't there to watch." The images also illustrate the steady melting along the water's edge that helps to undermine the bluffs even in the absence of storm activity.

The research team also deployed four submerged ocean buoys attached to metal sleds with sensors to measure the wave activity at different depths in the shallow coastal waters, comparing wave power with the shoreline fetch. The team attached temperature sensors to the buoy mooring lines to monitor seawater temperatures, which have been warming in recent summers due to increased solar radiation, he said.

When the sea ice is further from the shore, currents from the Beaufort and Chukchi seas transport warmer water to the coastline, said Anderson. While the temperature hovers around 45 degrees during the summer months, the shallow coastal water warmed to as much as 59 degrees during the 2007 field season -- the same year the largest loss of summer Arctic sea was recorded, he said.

As the ice wedges cut down through the polygon blocks, the surface soil above them -- which thaws each summer -- is pushed up slightly, forming small ridges that eventually surround each polygon, said Anderson. Small ponds form above individual polygons during the summer months as the surface ice and snow melts, providing habitat for migrating birds that feed and breed along the Beaufort Sea coastline.

"This is an important habitat for birds and other wildlife," said Anderson. "One of the concerns we have is that some larger ponds and lakes located slightly further inland may begin draining into the sea as the shoreline continues to recede."

While there are no towns adjacent to the specific study area, coastal erosion threatens abandoned military and petroleum infrastructure, he said. Coastal erosion occurs at similar sites elsewhere along Alaska's coastline. Bank stabilization measures using sandbags, for example, have been undertaken at the Alaskan town of Kaktovik on the Beaufort Sea in an attempt to slow the problem.

According to a 2009 CU-Boulder study, Arctic sea ice during the annual September minimum is now declining at a rate of 11.2 percent per decade. Only 19 percent of the ice cover was more than two years old -- the least ever recorded in the satellite record and far below the 1981-2000 summer average of 48 percent.

Brightest-Ever 'Blazar' Flare from Distant Galaxy Spotted by NASA's Fermi Gamma-Ray Space Telescope

2009-12-13T05:11:00.000-08:00

A galaxy located billions of light-years away is commanding the attention of NASA's Fermi Gamma-ray Space Telescope and astronomers around the globe. Thanks to a series of flares that began September 15, the galaxy is now the brightest source in the gamma-ray sky -- more than ten times brighter than it was in the summer.

Astronomers identify the object as 3C 454.3, an active galaxy located 7.2 billion light-years away in the constellation Pegasus. But even among active galaxies, it's exceptional.

"We're looking right down the barrel of a particle jet powered by the galaxy's supermassive black hole," said Gino Tosti at the National Institute of Nuclear Physics in Perugia, Italy. "Some change within that jet -- we don't know what -- is likely responsible for these flares."

Blazars, like many active galaxies, emit oppositely directed jets of particles traveling near the speed of light when matter falls toward their central supermassive black holes. What makes a blazar so bright in gamma rays is its orientation: One of the jets happens to be aimed straight at us.

Most of the time, the brightest persistent source in the gamma-ray sky is the Vela pulsar, which at a distance of about 1,000 light-years lies practically next door.

"3C 454.3 is millions of times farther away, yet the current flare makes it twice as bright as Vela," said Lise Escande at the Center for Nuclear Studies in Gradignan, near Bordeaux, France. "That represents an incredible energy release, and one the source can't sustain for very long."

According to Massimo Villata at Italy's Torino Observatory, 3C 454.3 also is flaring at radio and visible wavelengths, if less dramatically. "In red light, the blazar brightened by more than two and a half times to magnitude 13.7, and it is also very bright at high radio frequencies."

The Fermi team is alerting astronomers to monitor the event over as broad a range of wavelengths as possible. "That's our best bet for understanding what's going on inside that jet," Tosti said.

First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Sextuplet System

2009-12-13T05:10:00.000-08:00

In ancient times, people with exceptional vision discovered that one of the brightest stars in the Big Dipper was, in fact, two stars so close together that most people cannot distinguish them. The two stars, Alcor and Mizar, were the first binary stars -- a pair of stars that orbit each other -- ever known.

Modern telescopes have since found that Mizar is itself a pair of binaries, revealing what was once thought of as a single star to be four stars orbiting each other. Alcor has been sometimes considered a fifth member of the system, orbiting far away from the Mizar quadruplet.

Now, an astronomer at the University of Rochester and his colleagues have made the surprise discovery that Alcor is also actually two stars, and is apparently gravitationally bound to the Mizar system, making the whole group a sextuplet. This would make the Mizar-Alcor sextuplet the second-nearest such system known. The discovery is especially surprising because Alcor is one of the most studied stars in the sky.

"Finding that Alcor had a stellar companion was a bit of serendipity," says Eric Mamajek, assistant professor of physics and astronomy at the University of Rochester, and leader of the team that found the star. "We were trying a new method of planet hunting and instead of finding a planet orbiting Alcor, we found a star."

Mamajek says that a separate group of scientists, led by Ben Oppenheimer of the American Natural History Museum, has also just found that the Alcor companion is physically associated with the star.

That group has also recorded a rough spectrum of the star, which Mamajek says confirms his prediction that the companion is a cool and dim M-class dwarf star.

Mamajek and colleagues at the University of Arizona used the Multiple Mirror Telescope in Arizona, which has a secondary mirror capable of flexing slightly to compensate for the twinkling the Earth's atmosphere normally imparts to starlight. With the clearest images he could obtain of nearby stars, Mamajek's team used computer algorithms to remove as much glare as possible from the image of a star in the hopes of spotting a planet near the star. Planets are so much dimmer than their parent stars that spotting one is like trying to discern a firefly next to a spotlight from several miles away, says Mamajek.

Though Mamajek was unable to find any planets in the first group of stars he surveyed, he did stumble across the tiny star hidden in the glare of Alcor. Not only did Mamajek's project reveal the image of the star, but its presence was able to explain slight deviations in movement that scientists had noticed in Alcor. In addition, Mamajek estimates that the small companion star is likely a third as massive as our sun, and explains why astronomers have detected unexpectedly high levels of X-rays coming from Alcor -- dwarf stars naturally radiate high levels of X-rays.

"It's pretty exciting to have found a companion to this particular star," says Mamajek. "Alcor and Mizar weren't just the first known binaries -- the four stars that were once thought to be the single Mizar were discovered in lots of 'firsts' throughout history."

Benedetto Castelli, Galileo's protege and collaborator, first observed with a telescope that Mizar was not a single star in 1617, and Galileo observed it a week after hearing about this from Castelli, and noted it in his notebooks, says Mamajek. Those two stars, called Mizar A and Mizar B, together with Alcor, in 1857 became the first binary stars ever photographed through a telescope. In 1890, Mizar A was discovered to itself be a binary, being the first binary to be discovered using spectroscopy. In 1908, spectroscopy revealed that Mizar B was also a pair of stars, making the group the first-known quintuple star system.

Mamajek says some astronomers have raised the question of whether Alcor is truly a part of the system made up of the Mizar group of stars because Alcor's motion isn't what scientists would expect it to be if it were gravitationally connected to the Mizar group. Mamajek says that indeed Alcor is part of the same system, and that the influence of Alcor's newly discovered companion is partly responsible for Alcor's unexpected motion.

Mamajek is continuing his efforts to find planets around nearby stars, but his attention is not completely off Alcor and Mizar. "You see how the disk of Alcor B doesn't seem perfectly round?" says Mamajek, pointing toward an image of Alcor and its new companion. "Some of us have a feeling that Alcor might actually have another surprise in store for us."

Climate Change in Kuwait Bay: Higher Temperatures Having Profound Effects

2009-12-12T02:21:00.000-08:00

Since 1985, seawater temperature in Kuwait Bay, northern Persian Gulf, has increased on average 0.6°C per decade. This is about three times faster than the global average rate reported by the Intergovernmental Panel on Climate Change (IPCC). Differences are due to regional and local effects. Increased temperatures are having profound effects on key habitats and on power generation the Persian Gulf.

Researcher Dr Thamer Al-Rashidi of the National Oceanography Centre, Southampton, said: "Because the waters of Kuwait Bay are well mixed by the tides, measurements of sea surface temperature can be used to assess temperature trends over time in the bay as a whole."

He and his colleagues used data on sea surface temperature (1985-2007) remotely sensed by a number of polar orbiting satellites to assess warming in Kuwait Bay and the Gulf region.

The data were 'ground truthed' by direct measurements of sea surface temperature in the region, and are in accord with air temperature trends recorded at Kuwait airport, and verify trends found in satellite data.

They found that the sea surface temperature of Kuwait Bay increased over the period at an average rate of around 0.62°C per decade, with an uncertainty of plus or minus 0.01°C. This is about three times the rate of average global increase estimated by the IPCC.

The increase was greatest in the early summer and least during winter months. The length of summertime increased almost twice as fast as peak summertime temperature. In 1998 and 2003, the monthly measurements of sea surface temperature showed unusually high peaks in summer temperature coincident with El Niño events -- periodic warming of the atmosphere and ocean affecting weather in many parts of the world.

Temperature dipped in 1991, in the aftermath of the Iraqi invasion of Kuwait. "Dense smoke from the burning of oil fields hung over the region blocking out the sun, and we believe that this atmospheric dimming caused the relatively low summertime temperature peak recorded that year," said Dr Al-Rashidi, himself an officer in the Kuwaiti Navy. However, temperature then increased fairly steadily between 1992 and 2004.

"What all of this tells us," says Dr Al-Rashidi, "is that the global trends reported by the IPCC may not be representative locally."

The researchers estimate that about a third (0.2°C) of the observed decadal increase in seawater temperature in Kuwait Bay can be attributed to global climate change, while around 13 per cent of the increase (0.08°C) is due to human activity along the coast of the bay, especially the direct impacts of power and desalination plants.

The remaining 0.3°C (50 per cent) of decadal warming appears to be due to changes in regional drivers, including circulation and mixing of seawater in the Persian Gulf, the influence of the dominant north-westerly wind (Shamal), freshwater discharge from the Euphrates and Tigris rivers, and sand storms.

Increased seawater temperatures are likely responsible, at least in part, for the reduction in dissolved oxygen causing summertime fish kills, and also for coral bleaching in the region. In general, the researchers warn that increased temperatures may lead to serious environmental degradation in the sensitive marine ecosystems of the Persian Gulf.

Dr Al-Rashidi argues that regional warming could also have strategic implications: "Kuwait is dependent on desalination plants for its fresh water, and at temperatures over 37-38°C the turbines generating the electricity driving these plants have to be turned off," he said.

However, there have been distinct reductions in temperature since 2004 due to dust storms and their effect solar dimming. The frequency of dust storms has increased in recent years due to decreasing rainfall and increasing desertification. How this will interact with other local, regional and global factors to affect average temperatures in the long term remains uncertain.

"The lesson learnt is that temperature trends that we experience may be quite different from place to place due to variations in local and regional effects," said Dr Al-Rashidi.

Sea Level Is Rising Along US Atlantic Coast, Say Environmental Scientists

2009-12-11T05:40:00.000-08:00

An international team of environmental scientists led by the University of Pennsylvania has shown that sea-level rise along the Atlantic Coast of the United States was 2 millimeters faster in the 20th century than at any time in the past 4,000 years.

Sea-level rise prior to the 20th century is attributed to coastal subsidence. Put simply, land is being lost to subsidence as the earth continues to rise in response to the removal of the huge weight of ice sheets during the last glacial period. Using sediment cores from the U.S. Atlantic coast, researchers found significant spatial variations in land movement, with the mid-Atlantic coastlines of New Jersey, Delaware and Maryland subsiding twice as much as areas to the north and south. Coastal subsidence enhances sea-level rise, which leads to shoreline erosion and loss of wetlands and threatens coastal populations.

Researchers corrected relative sea-level data from tide gauges using the coastal-subsidence values. Results clearly show that the 20th-century rate of sea-level rise is 2 millimeters higher than the background rate of the past 4,000 years. Furthermore, the magnitude of the sea-level rise increases in a southerly direction from Maine to South Carolina. This is the first demonstrated evidence of this phenomenon from observational data alone. Researchers believe this may be related to the melting of the Greenland Ice Sheet and ocean thermal expansion.

"There is universal agreement that sea level will rise as a result of global warming but by how much, when and where it will have the most effect is unclear," said Benjamin P. Horton, assistant professor in the Department of Earth and Environmental Science at Penn. "Such information is vital to governments, commerce and the general public. An essential prerequisite for accurate prediction is understanding how sea level has responded to past climate changes and how these were influenced by geological events such as land movements."

The study provides the first accurate dataset for sea-level rise for the U.S. Atlantic coast, identifying regional differences that arise from variations in subsidence and demonstrate the possible effects of ice-sheet melting and thermal expansion for sea level rise.

The results appear in the Dec. 1 issue of the journal Geology. The study was supported by the National Science Foundation, the Thouron Family and the University of Pennsylvania.

Early Carnivorous Dinosaur Crossed Continents, Alters Evolutionary Tree

2009-12-11T05:38:00.000-08:00

Did the first dinosaurs wander across continents or stay put where they first evolved? The first dinosaurs evolved 230 million years ago when the continents were assembled into one landmass called Pangea. The question of early dinosaur movements remained unclear until the discovery of some exciting new fossils.

In the Dec. 11, 2009, issue ofScience, a team of paleontologists presents the 213-million-year-old fossils of previously unknown carnivorous dinosaur Tawa hallae,including several of the best preserved dinosaur skeletons from the Triassic Period.

Fossil bones of Tawa, named after the Hopi word for the Puebloan sun god, were recovered from a dig site in northern New Mexico known as Hayden Quarry. The quarry is located on Ghost Ranch, where late painter Georgia O'Keefe once lived. Fossil bones of several individuals were recovered, but the type specimen is a nearly complete skeleton of a juvenile that stood about 28 inches (70 centimeters) tall at the hips and was approximately 6 feet (about 2 meters) long, from snout to tail. Its body was about the size of a large dog, but with a much longer tail.

Based on an analysis of the relationships among Tawa and other early dinosaurs, the researchers hypothesize that dinosaurs originated in a part of Pangea that is now South America, diverging into theropods (like Tyrannosaurus rex), sauropodomorphs (like Apatosaurus) and ornithischians (like Triceratops); and then dispersed more than 220 million years ago across parts of Pangea that later became separate continents.

"This new dinosaur Tawa hallae changes our understanding of the relationships of early dinosaurs, and provides fantastic insight into the evolution of the skeleton of the first carnivorous dinosaurs" said Randall Irmis of the Utah Museum of Natural History and University of Utah, a co-author of the study.

In addition to Irmis, authors of the study included lead author Sterling Nesbit of the University of Texas at Austin; Nathan Smith of the University of Chicago and the Field Museum of Natural History; Alan Turner of Stony Brook University; Alex Downs of the Ruth Hall Museum of Paleontology in Abiquiu, N.M.; and Mark Norell of the American Museum of Natural History.

"If you have continents splitting apart, you get isolation," said Nesbitt. "So when barriers develop, you would expect that multiple carnivorous dinosaurs in a region should represent a closely related endemic radiation. But that is what we don't see in early dinosaur evolution."

Instead, the research team found three distinct carnivorous dinosaurs -- including the newly discovered Tawa -- in the fossil-rich, Late Triassic beds they investigated at Ghost Ranch. "When we analyzed the evolutionary relationships of these dinosaurs, we discovered that they were only distantly related, and that each species had close relatives in South America," said Irmis. "This implies that each carnivorous dinosaur species descended from a separate lineage before arriving in [the part of Pangea that is now] North America, instead of all evolving from a local ancestor."

At Ghost Ranch, the researchers found fossils from a carnivorous dinosaur related to Coelophysis, common to that region, and fossils from a carnivore closely related to Herrerasaurus, which lived in South America. The 6.6- to 13-foot-long (2- to 4-meter-long) skeletons of Tawa display characteristics that exist in both species and features found in neither, implying a separate lineage.

"The discovery of multiple dinosaur species in one place that emigrated from elsewhere got us wondering whether other Late Triassic reptiles show similar patterns" said Irmis. "It turns out a variety of other reptile groups made multiple trips from the northern and southern continents [then parts of Pangea] and back again during the Late Triassic, including other dinosaurs."

Because so many different groups with different life modes were able to move freely across Pangea, the research team concluded that during the Late Triassic, there were no major physical barriers, such as large mountain ranges, to the movement of reptiles between parts of Pangea that later separated into distinct continents.

But this presented a paradox to the team: "We wondered: if reptiles, including dinosaurs, were able to freely move around Pangea during the Late Triassic, then why aren't there any sauropodomorph and ornithischian dinosaurs in North America during the Triassic?" said Irmis. "Our conclusion is that climate, possibly related to latitude, controlled the distributions of some reptile species."

"We think that all the major dinosaur groups had the ability to get to North America [part of Pangea] during the Late Triassic, and may have even passed through, but for some reason, only the carnivorous dinosaurs found the North American climate to be hospitable during this time," concluded Irmis.

The first Tawa fossils were discovered in 2004 by volunteers taking a paleontology seminar at the Ruth Hall Museum of Paleontology in New Mexico. Museum scientists invited the team of paleontologists to come and take a look.

"The specimens are unusual because they are so well preserved," said Irmis. "Because dinosaur bones are hollow, they are usually broken and crushed, but those of Tawa are nearly pristine."

Irmis and the rest of the team began a full-scale excavation in 2006 and have continued to unearth new material every summer since then. The fossil bone bed extends for tens of yards along a hillside, promising many years of potential significant finds.

Snowflake Chemistry Could Give Clues About Ozone Depletion

2009-12-10T06:36:00.000-08:00

There is more to the snowflake than its ability to delight schoolchildren and snarl traffic.

The structure of the frosty flakes also fascinate ice chemists like Purdue University's Travis Knepp, a doctoral candidate in analytical chemistry who studies the basics of snowflake structure to gain more insight into the dynamics of ground-level, or "tropospheric," ozone depletion in the Arctic.

"A lot of chemistry occurs on ice surfaces," Knepp said. "By better understanding the physical structure of the snow crystal -- how it grows and why it takes a certain shape -- we can get a better idea of the chemistry that occurs on that surface."

His work on snowflake shape and how temperature and humidity affect it takes place in a special laboratory chamber no larger than a small refrigerator. Knepp can "grow" snow crystals year-round on a string inside this chamber. The chamber's temperature ranges from 100-110 degrees Fahrenheit down to minus 50 degrees Fahrenheit.

Knepp, under the direction of Paul Shepson, professor and head of Purdue's Department of Chemistry, is studying snow crystals and why sharp transitions in shape occur at different temperatures. The differences he sees not only explain why no two snowflakes are identical, but also hold implications for his ozone research in the Arctic Ocean region.

"On the surface of all ice is a very thin layer of liquid water," Knepp said. "Even if you're well below the freezing point of water, you'll have this very thin layer of water that exists as a liquid form. That's why ice is slippery. Whenever you slip, you're not slipping on ice, you're slipping on that thin layer of water."

This thin, or quasi-liquid, layer of water exists on the top and sides of a snow crystal. Its presence causes the crystal to take on different forms as temperature and humidity change.

For example, the sides of a crystal growing in a warmer range of 27-32 degrees Fahrenheit expand much faster than the top or bottom, causing it to take on a platelike structure. Between 14 and 27 degrees Fahrenheit, crystals look like tall, solid prisms or needles.

"As you increase the humidity, you'll get more branching," Knepp said.

Snow crystals transition to other shapes, and sometimes even back and forth, as the temperature and humidity change.

"The bottom line is that the thickness or the presence of this really thin layer of water is what dictates the general shape that the snow crystal takes," Knepp said. "By altering the quasi-liquid layer's thickness, we changed the temperature at which the snow crystal changes shape.

"Until now, nobody knew that the quasi-liquid layer had such a significant role in determining the shape of snow crystals. Our research clearly shows this to be the case."

This knowledge has application for Knepp and his colleagues in their ozone work.

"Most people have probably heard of ozone depletion in the North and South Poles. This occurs in the stratosphere, about 15 miles up," Knepp said. "What people don't know is that we also see ozone levels decrease significantly at ground level."

Ground-level ozone is very important. It gives the atmosphere the ability to clean itself. However, it also is toxic to humans and vegetation at high concentrations, like those found in smog, Shepson said.

Complex chemical reactions regularly take place on the snow's surface. These reactions, which involve the thin layer of water found on the surface of snow crystals, cause the release of certain chemicals that reduce ozone at ground level.

"How fast these reactions occur is partially limited by the snow crystals' surface area," Knepp said. "Snow crystals with more branching will have higher surface areas than non-branched snow crystals, which will allow the rate of reaction to increase."

The need to understand these intricate chemical reactions and their implications for ozone reduction drive the researchers to continue studying snow.

"As the impact of emissions from human activities continues to grow, we need to be able to understand the impact of global average ozone," Shepson said. "Understanding ice and snow is part of that."

Saturn's Mysterious Hexagon Emerges from Winter Darkness

2009-12-10T06:31:00.000-08:00

After waiting years for the sun to illuminate Saturn's north pole again, cameras aboard NASA's Cassini spacecraft have captured the most detailed images yet of the intriguing hexagon shape crowning the planet.

The last visible-light images of the entire hexagon were captured by NASA's Voyager spacecraft nearly 30 years ago, the last time spring began on Saturn. After the sunlight faded, darkness shrouded the north pole for 15 years. Much to the delight and bafflement of Cassini scientists, the location and shape of the hexagon in the latest images match up with what they saw in the Voyager pictures.

"The longevity of the hexagon makes this something special, given that weather on Earth lasts on the order of weeks," said Kunio Sayanagi, a Cassini imaging team associate at the California Institute of Technology. "It's a mystery on par with the strange weather conditions that give rise to the long-lived Great Red Spot of Jupiter."

The hexagon was originally discovered in images taken by the Voyager spacecraft in the early 1980s. It encircles Saturn at about 77 degrees north latitude and has been estimated to have a diameter wider than two Earths. The jet stream is believed to whip along the hexagon at around 100 meters per second (220 miles per hour).

Early hexagon images from Voyager and ground-based telescopes suffered from poor viewing perspectives. Cassini, which has been orbiting Saturn since 2004, has a better angle for viewing the north pole. But the long darkness of Saturnian winter hid the hexagon from Cassini's visible-light cameras for years. Infrared instruments, however, were able to obtain images by using heat patterns. Those images showed the hexagon is nearly stationary and extends deep into the atmosphere. They also discovered a hotspot and cyclone in the same region.

The visible-light cameras of Cassini's imaging science subsystem, which have higher resolution than the infrared instruments and the Voyager cameras, got their long-awaited glimpse of the hexagon in January, as the planet approached equinox. Imaging team scientists calibrated and stitched together 55 images to create a mosaic and three-frame movie. The mosaics do not show the region directly around the north pole because it had not yet fully emerged from winter night at that time.

Scientists are still trying to figure out what causes the hexagon, where it gets and expels its energy and how it has stayed so organized for so long. They plan to search the new images for clues, taking an especially close look at the newly identified waves that radiate from the corners of the hexagon -- where the jet takes its hardest turns -- and the multi-walled structure that extends to the top of Saturn's cloud layer in each of the hexagon's six sides. Scientists are also particularly intrigued by a large dark spot that appeared in a different position in a previous infrared image from Cassini. In the latest images, the spot appears in the 2 o'clock position.

Because Saturn does not have land masses or oceans on its surface to complicate weather the way Earth does, its conditions should give scientists a more elementary model to study the physics of circulation patterns and atmosphere, said Kevin Baines, an atmospheric scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who has studied the hexagon with Cassini's visual and infrared mapping spectrometer.

"Now that we can see undulations and circular features instead of blobs in the hexagon, we can start trying to solve some of the unanswered questions about one of the most bizarre things we've ever seen in the solar system," Baines said. "Solving these unanswered questions about the hexagon will help us answer basic questions about weather that we're still asking about our own planet."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the Cassini mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.

Ventriloquist Birds Call to Warn Friends and Enemies

2009-12-08T01:11:00.000-08:00

Birds' alarm calls serve both to alert other birds to danger and to warn off predators. And some birds can pull a ventriloquist's trick, singing from the side of their mouths, according to a UC Davis study.

Many animals respond vocally when they detect predators, but it's not clear to whom they are signaling, said Jessica Yorzinski, a graduate student in animal behavior at UC Davis who conducted the study with Gail Patricelli, professor of evolution and ecology. They might be warning others of the threat, but they might also be telling the predator, "I've seen you."

Yorzinski used a ring of directional microphones around a birdcage to record the songs of dark-eyed juncos, yellow-rumped warblers, house finches and other birds as they were shown a stuffed owl. All the birds were captured in the wild, tested, banded and released within 24 hours.

Overall, the birds' alarm calls were relatively omnidirectional, suggesting that they were given to warn other birds in the vicinity. However, the main species tested -- juncos, warblers and finches -- all showed an ability to focus their calls in the direction of the owl, so these calls could also function to warn off a predator.

House finches were the least directional in their calls. They are also the most social of the species tested, Yorzinski noted.

Some of the birds were able to project a call in one direction while their beak was pointed in another.

"It's like talking out of the corner of their mouths," Yorzinski said. In some cases the birds may see better sideways than forwards, although Yorzinski did record evidence of birds projecting calls both forward and to either side.

"It's not clear how they're accomplishing this," Yorzinski said.

The study was published Nov. 18 in the journal Proceedings of the Royal Society B and was funded by the National Science Foundation.

Lizard Changes Its Diet to Avoid Predators

2009-12-08T01:09:00.000-08:00

A scientist from the University of Salamanca and another from Yale University have shown that the presence of predators affects the behaviour of Acanthodactylus beershebensis, a lizard species from the Negev Desert in Israel. According to the study, these reptiles move less and catch less mobile and different prey if they are under pressure from predators.

Many theoretical models had predicted this result, but until now there had been very few experimental trials and none in the case of saurians (reptiles). This experiment by Dror Hawlena, a researcher at Yale University in the United States, and Valentín Pérez-Mellado, a researcher at the University of Salamanca, has shown that certain animals, such as the insectivore lizard Acanthodactylus beershebensis, can change their behaviour and diet to avoid being eaten.

"When there is greater pressure from predators, the individuals tend to move less and catch more mobile prey from somewhat different groups. The lizards' diet and food-seeking behaviour changed significantly when we experimentally increased the predation pressure on them," says Pérez-Mellado.

The study, published recently in the journal Oecologia, shows that reptiles threatened by predators become less selective and eat a more diverse range of foods, according to Pérez-Mellado, who was in charge of analysing their diet in Spain. The field work done over the summer months in 2000 and 2001 in the Negev Desert in Israel was carried out by Hawlena.

The scientists studied the species' diet data (trophic ecology) in two different situations -- with and without predators. The Spanish researcher analysed the contents of 327 faecal pellets taken from 291 different lizards in order to reconstruct their diet. Ants were the prey most commonly consumed by the lizards, both by those at risk (69.32%) and the controls (67.12%), followed by insects such as termites (19.14% and 19.17% respectively). The difference could be clearly seen in the consumption of seeds, because the lizards hardly consumed these (0.52%) when they were under threat from predators.

An ingenious experiment in the desert

In order to reach these conclusions, Hawlena, who is from the University of the Negev in Israel, designed an experiment that made it possible to prove that the presence of predators affects the behaviour and ecology of this endemic species. "A series of artificial perches were placed in a desert site, which made it easier for shrikes (small birds of prey that catch lizards) to make use of the area, since they could detect the lizards from raised perches such as trees and bushes. These perches were not placed in a similar site nearby, which was used as the control site," explains Pérez-Mellado.

Earth More Sensitive to Carbon Dioxide Than Previously Thought

2009-12-07T07:24:00.000-08:00

In the long term, the Earth's temperature may be 30-50% more sensitive to atmospheric carbon dioxide than has previously been estimated, reports a new study published inNature Geoscience.

The results show that components of the Earth's climate system that vary over long timescales -- such as land-ice and vegetation -- have an important effect on this temperature sensitivity, but these factors are often neglected in current climate models.

Dan Lunt, from the University of Bristol, and colleagues compared results from a global climate model to temperature reconstructions of the Earth's environment three million years ago when global temperatures and carbon dioxide concentrations were relatively high. The temperature reconstructions were derived using data from three million-year-old sediments on the ocean floor.

Lunt said, "We found that, given the concentrations of carbon dioxide prevailing three million years ago, the model originally predicted a significantly smaller temperature increase than that indicated by the reconstructions. This led us to review what was missing from the model."

The authors demonstrate that the increased temperatures indicated by the reconstructions can be explained if factors that vary over long timescales, such as land-ice and vegetation, are included in the model. This is primarily because changes in vegetation and ice lead to more sunlight being absorbed, which in turn increases warming.

Including these long-term processes in the model resulted in an increased temperature response of the Earth to carbon dioxide, indicating that the Earth's temperature is more sensitive to carbon dioxide than previously recognised. Climate models used by bodies such as the Intergovernmental Panel on Climate Change often do not fully include these long-term processes, thus these models do not entirely represent the sensitivity of the Earth's temperature to carbon dioxide.

Alan Haywood, a co-author on the study from the University of Leeds, said "If we want to avoid dangerous climate change, this high sensitivity of the Earth to carbon dioxide should be taken into account when defining targets for the long-term stabilisation of atmospheric greenhouse-gas concentrations."

Lunt added: "This study has shown that studying past climates can provide important insights into how the Earth might change in the future."

(a) shows predicted global temperatures when processes that adjust on relatively short-term timescales (for example sea-ice, clouds, and water vapour) are included in the model

(b) includes additional long-tem processes that adjust on relatively long timescales (vegetation and land-ice).

'Killer Petunias' Should Join the Ranks of Carnivorous Plants, Scientists Propose

2009-12-07T07:20:00.000-08:00

Scientists from the Royal Botanic Gardens, Kew and the Natural History Museum believe that carnivorous behaviour in plants is far more widespread than previously thought, with many commonly grown plants -- such as petunias -- at least part way to being "meat eaters." A review paper, Murderous plants: Victorian Gothic, Darwin and modern insights into vegetable carnivory.

Carnivorous plants have caught the imagination of humans since ancient times, and they fitted well into the Victorian interest in Gothic horrors. Accounts of man-eating plants published in 19th century works have long since been discredited, but they continue to appear in different media including films (Audrey II in Little Shop of Horrors) and books (Tentacula in the Harry Potter series). Even popular Japanese cartoon Pokémon includes some characters based on carnivorous plants (Bellsprout, Weepinbell and Victreebell).

Carnivorous plants fascinated Charles Darwin, and he and his friend Sir Joseph Hooker (Director of the Royal Botanic Gardens, Kew at that time) had an extensive correspondence concerning them. Darwin's book Insectivorous Plants played a critical role in the idea that plants could eat animals being generally accepted. Before this, many botanists (including Linnaeus) had refused to accept that this could be the case.

Since Darwin's time, several groups have been generally recognised as carnivorous plants (including sundews, Venus flytraps and pitcher plants). Various other plants have been suggested as possible carnivores by some authors, but wide acceptance of these has failed to materialise. Defining what constitutes carnivory in plants is a challenge, and authors include or exclude groups of plants on the basis of different sets of criteria. Professor Mark Chase and co-authors from the Royal Botanic Gardens, Kew and the Natural History Museum contend that carnivory and non-carnivory should not be treated as a black and white situation, and they view plants as being on a sliding scale between those that show no carnivorous characteristics and those that are real "meat eaters" such as the Venus flytrap.

Plants like petunias and potatoes have sticky hairs that trap insects, and some species of campion have the common name catchfly for the same reason. However, some of the commonly accepted carnivores have not been demonstrated to have the ability to digest the insects they trap or to absorb the breakdown products. In their paper, Chase et al. review each of the groups of potential carnivores.

Professor Mark Chase, Keeper of the Jodrell Laboratory at the Royal Botanic Gardens, Kew says, "Although a man-eating tree is fictional, many commonly grown plants may turn out to be cryptic carnivores, at least by absorbing through their roots the breakdown products of the animals that they ensnare. We may be surrounded by many more murderous plants than we think."

Young Star Cluster Trumpler 14 Revealed in Stunning Image

2009-12-05T02:50:00.000-08:00

The young star cluster Trumpler 14 is revealed in another stunning ESO image. The amount of exquisite detail seen in this portrait, which beautifully reveals the life of a large family of stars, is due to the Multi-conjugate Adaptive optics Demonstrator (MAD) on ESO's Very Large Telescope. Never before has such a large patch of sky been imaged using adaptive optics ^[1], a technique by which astronomers are able to remove most of the atmosphere's blurring effects.

Noted for harbouring Eta Carinae -- one of the wildest and most massive stars in our galaxy -- the impressive Carina Nebula also houses a handful of massive clusters of young stars. The youngest of these stellar families is the Trumpler 14 star cluster, which is less than one million years old -- a blink of an eye in the Universe's history. This large open cluster is located some 8000 light-years away towards the constellation of Carina (the Keel).

A team of astronomers, led by Hugues Sana, acquired astounding images of the central part of Trumpler 14 using the Multi-conjugate Adaptive optics Demonstrator (MAD, ^[2]) mounted on ESO's Very Large Telescope (VLT). Thanks to MAD, astronomers were able to remove most of the blurring effects of the atmosphere and thus obtain very sharp images. MAD performs this correction over a much larger patch of the sky than any other current adaptive optics instrument, allowing astronomers to make wider, crystal-clear images.

Thanks to the high quality of the MAD images, the team of astronomers could obtain a very nice family portrait. They found that Trumpler 14 is not only the youngest -- with a refined, newly estimated age of just 500 000 years -- but also one of the most populous star clusters within the nebula. The astronomers counted about 2000 stars in their image, spanning the whole range from less than one tenth up to a factor of several tens of times the mass of our own Sun. And this in a region which is only about six light-years across, that is, less than twice the distance between the Sun and its closest stellar neighbour!

The most prominent star is the supergiant HD 93129A, one of the most luminous stars in the Galaxy. This titan has an estimated mass of about 80 times that of the Sun and is approximately two and a half million times brighter! It makes a stellar couple -- a binary star -- with another bright, massive star. The astronomers found that massive stars tend to pair up more often than less massive stars, and preferably with other more massive stars.

The Trumpler 14 cluster is undoubtedly a remarkable sight to observe: this dazzling patch of sky contains several white-blue, hot, massive stars, whose fierce ultraviolet light and stellar winds are blazing and heating up the surrounding dust and gas. Such massive stars rapidly burn their vast hydrogen supplies -- the more massive the star, the shorter its lifespan. These giants will end their brief lives dramatically in convulsive explosions called supernovae, just a few million years from now.

A few orange stars are apparently scattered through Trumpler 14, in charming contrast to their bluish neighbours. These orange stars are in fact stars located behind Trumpler 14. Their reddened colour is due to absorption of blue light in the vast veils of dust and gas in the cloud.

The technology used in MAD to correct for the effect of the Earth's atmosphere over large areas of sky will play a crucial role in the success of the next generation European Extremely Large Telescope (E-ELT).

Notes:

[1] Telescopes on the ground suffer from a blurring effect introduced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way that delights poets but frustrates astronomers, since it smears out the fine details of the images. However, with adaptive optics techniques, this major drawback can be overcome so that the telescope produces images that are as sharp as theoretically possible, i.e. approaching conditions in space. Adaptive optics systems work by means of a computer-controlled deformable mirror that counteracts the image distortion introduced by atmospheric turbulence. It is based on real-time optical corrections computed at very high speed (several hundreds of times each second) from image data obtained by a wavefront sensor (a special camera) that monitors light from a reference star.

[2] Present adaptive optics systems can only correct the effect of atmospheric turbulence in a very small region of the sky -- typically 15 arcseconds or less -- the correction degrading very quickly when moving away from the reference star. Engineers have therefore developed new techniques to overcome this limitation, one of which is multi-conjugate adaptive optics. MAD uses up to three stars instead of one as references to remove the blur caused by atmospheric turbulence over a field of view thirty times larger than that available to existing techniques (ESO PR 19/07).

First Direct Observation of a Planet-Like Object Orbiting Star Similar to Sun

2009-12-05T02:48:00.000-08:00

An international team of scientists that includes an astronomer from Princeton University has made the first direct observation of a planet-like object orbiting a star similar to the sun.

The finding marks the first discovery made with the world's newest planet-hunting instrument on the Hawaii-based Subaru Telescope and is the first fruit of a novel research collaboration announced by the University in January.

The object, known as GJ 758 B, could be either a large planet or a "failed star," also known as a brown dwarf. The faint companion to the sun-like star GJ 758 is estimated to be 10 to 40 times as massive as Jupiter and is a "near neighbor" in our Milky Way galaxy, hovering a mere 300 trillion miles from Earth.

"It's a groundbreaking find because one of the current goals of astronomy is to directly detect planet-like objects around stars like our sun," said Michael McElwain, a postdoctoral research fellow in Princeton's Department of Astrophysical Sciences who was part of the team that made the discovery. "It is also an important verification that the system -- the telescope and its instruments -- is working well."

Images of the object were taken in May and August during early test runs of the new observation equipment. The team has members from Princeton, the University of Hawaii, the University of Toronto, the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, and the National Astronomical Observatory of Japan (NAOJ) in Tokyo. The results will be published in the Astrophysical Journal Letters.

"This challenging but beautiful detection of a very low mass companion to a sun-like star reminds us again how little we truly know about the census of gas giant planets and brown dwarfs around nearby stars," said Alan Boss, an astronomer at the Carnegie Institution for Science in Washington, D.C., who was not involved in the research. "Observations like this will enable theorists to begin to make sense of how this hitherto unseen population of bodies was able to form and evolve."

Brown dwarfs are stars that are not massive enough to sustain fusion reactions at their core, so they burn out and cool off as they age.

Aided by new varieties of viewing techniques, scientists started finding extrasolar planets (planets beyond the solar system) in 1992 and have located more than 400 planet-like objects so far. Most, however, have not been directly observed, but inferred from viewing the star around which the planet orbits. GJ 758 B is one of the first planet-like objects to be directly seen. Of the others that have been directly viewed, most have been on larger orbits than the distance between GJ 758 B and its star, or around stars with temperatures far above the average temperature of GJ 758 or our sun.

Scientists were able to spot the object even though it was hidden in the glare of the star it orbits by subtracting out that brighter light. To do this, they used the High Contrast Coronagraphic Imager with Adaptive Optics that has been attached to the Subaru Telescope. Also known as HiCIAO, it is part of a new generation of instruments specially made to detect faint objects near a bright star by masking its far more intense light. They also employed a technique known as angular differential imaging to capture the images.

"It's amazing how quickly this instrument has come online and burst into the forefront," said Marc Kuchner, an exoplanet scientist at the NASA Goddard Space Flight Center in Greenbelt, Md., who was not involved in the work. "I think this is just the beginning of what HiCIAO is going to do for the field." He added that the discovery also emphasizes that this new method of finding exoplanets -- direct detection -- is "really hitting its stride."

The planet-like object is currently at least 29 times as far from its star as the Earth is from the sun, approximately as far as Neptune is from the sun. However, further observations will be required to determine the actual size and shape of its orbit. At a temperature of only 600 F, the object is relatively "cold" for a body of its size. It is the coldest companion to a sun-like star ever recorded in an image.

The fact that such a large planet-like object appears to orbit at this location defies traditional thinking on planet formation. It is thought most larger planets are formed either closer to or farther from stars, but not in the location where GJ 758 is now. Discoveries such as this one could help theorists refine their ideas.

Telescope images also revealed a second companion to the star, which the scientists have called GJ 758 C. More observations, however, are needed to confirm whether it is nearby or just looks that way. "It looks very promising," said Christian Thalmann, one of the team's lead scientists. If it should turn out to be a second companion, he said, that would make both B and C more likely to be young planets rather than old brown dwarfs, since two brown dwarfs in such close proximity would not remain stable for such a long period of time.

Researchers from Princeton and NAOJ announced an agreement on Jan. 15 to collaborate over the next 10 years, using new equipment on the Subaru Telescope to peer into hidden corners of the nearby universe and ferret out secrets from its distant past. This research is a part of that collaboration. The HiCIAO team is led by Professor Motohide Tamura of NAOJ.

The partnership, called the NAOJ-Princeton Astrophysics Collaboration or N-PAC, provides for the exchange of scientific resources and supports a variety of long-term research projects in which the scientists from both Princeton and the Japanese astronomical community will participate on an equal basis. The collaboration builds on a decades-long tradition of scientific collaboration between Japanese and Princeton astronomers in a wide range of astronomical fields.

An important part of that partnership is the search for planets, previously hidden by the glare of stars. Finding these planets is a crucial step in answering the age-old question of the existence of extraterrestrial life.

Superbright Supernova Is First of Its Kind

2009-12-05T02:46:00.001-08:00

An extraordinarily bright, extraordinarily long-lasting supernova named SN 2007bi, snagged in a search by a robotic telescope, turns out to be the first example of the kind of stars that first populated the Universe. The superbright supernova occurred in a nearby dwarf galaxy, a kind of galaxy that's common but has been little studied until now, and the unusual supernova could be the first of many such events soon to be discovered.

SN 2007bi was found early in 2007 by the international Nearby Supernova Factory (SNfactory) based at the U.S. Department of Energy's Lawrence Berkeley National Laboratory. The supernova's spectrum was unusual, and astronomers at the University of California at Berkeley subsequently obtained a more detailed spectrum. Over the next year and a half the Berkeley scientists participated in a collaboration led by Avishay Gal-Yam of Israel's Weizmann Institute of Science to collect and analyze much more data as the supernova slowly faded away.

The analysis indicated that the supernova's precursor star could only have been a giant weighing at least 200 times the mass of our Sun and initially containing few elements besides hydrogen and helium -- a star like the very first stars in the early Universe.

"Because the core alone was some 100 solar masses, the long-hypothesized phenomenon called pair instability must have occurred," says astrophysicist Peter Nugent. A member of the SNfactory, Nugent is the co-leader of the Computational Cosmology Center (C3), a collaboration between Berkeley Lab's Physics Division and Computational Research Division (CRD), where Nugent is a staff scientist. "In the extreme heat of the star's interior, energetic gamma rays created pairs of electrons and positrons, which bled off the pressure that sustained the core against collapse."

"SN 2007bi was the explosion of an exceedingly massive star," says Alex Filippenko, a professor in the Astronomy Department at UC Berkeley whose team helped obtain, analyze, and interpret the data. "But instead of turning into a black hole like many other heavyweight stars, its core went through a nuclear runaway that blew it to shreds. This type of behavior was predicted several decades ago by theorists, but never convincingly observed until now."

SN 2007bi is the first confirmed observation of a pair-instability supernova. The researchers describe their results in the 3 December 2009 issue of Nature.

On the trail of a strange beast

SN 2007bi was recorded on images taken as part of the Palomar-QUEST Survey, an automated search with the wide-field Oschin Telescope at the California Institute of Technology's Palomar Observatory, and was quickly detected and categorized as an unusual supernova by the SNfactory. The SNfactory has so far discovered nearly a thousand supernovae of all types and amassed thousands of spectra, but has focused on those designated Type Ia, the "standard candles" used to study the expansion history of the Universe. SN 2007bi, however, turned out not to be a Type Ia. For one thing, it was at least ten times as bright.

"The thermonuclear runaway experienced by the core of SN 2007bi is reminiscent of that seen in the explosions of white dwarfs as Type Ia supernovae," says Filippenko, "but on a much larger scale and with a far greater amount of power."

"The discovery is a great example of how we can get all the science, in addition to cosmology, out of the SNfactory search," says Greg Aldering, SNfactory project leader, who was not an author of the Nature paper. "Berkeley Lab and Caltech's Astronomy Department agreed that we would split the work, the Lab handling the Type Ia's and Caltech all the other types."

Nugent contacted Gal-Yam, then a Caltech postdoctoral fellow, the lead investigator for the all-other category. "I asked, are you interested? He said, sure!" Nugent then contacted Filippenko, who was about to conduct a night of observation with the 10-meter Keck I telescope on the summit of Mauna Kea in Hawaii. Filippenko immediately set out to obtain an optical spectrum of the unusual supernova.

Caltech researchers subsequently acquired additional spectra with the Keck telescope, as did Paolo Mazzali's team from the Max Planck Institute for Astrophysics in Garching, Germany, using the Very Large Telescope (VLT) in Chile.

Says Mazzali, "The Keck and VLT spectra clearly indicated that an extremely large amount of material was ejected by the explosion, including a record amount of radioactive nickel, which caused the expanding gases to glow very brightly."

Rollin Thomas of CRD, a member of C3 and the SNfactory, aided the early analysis, using the Franklin supercomputer at the National Energy Research Scientific Computing Center (NERSC) to run a code he developed to generate numerous synthetic spectra for comparison with the real spectrum.

"The code uses hundreds of cores to systematically test a large number of simplified model supernovae, searching through the candidates by adjusting parameters until it finds a good fit," says Thomas. "This kind of data-driven approach is key to helping us understand new types of transients for which no reliable theoretical predictions yet exist." The model fit was unambiguous: SN 2007bi was a pair-instability supernova.

"The central part of the huge star had fused to oxygen near the end of its life, and was very hot," Filippenko explains. "Then the most energetic photons of light turned into electron-positron pairs, robbing the core of pressure and causing it to collapse. This led to a nuclear runaway explosion that created a large amount of radioactive nickel, whose decay energized the ejected gas and kept the supernova visible for a long time."

Gal-Yam organized a team of collaborators from many institutions to continue to observe SN 2007bi and obtain data as it slowly faded over a span of 555 days. Says Gal-Yam, "As our follow-up observations started to roll in, I immediately realized this must be something new. And indeed it turned out to be a fantastic example of how we are finding new types of stellar explosions."

Because it had no hydrogen or helium lines, the usual classification scheme would have labeled the supernova a Type Ic. But it was so much brighter than an ordinary Type Ic that it reminded Nugent of only one prior event, a supernova designated SN 1999as, found by the international Supernova Cosmology Project but unfortunately three weeks after its peak brightness.

Understanding a supernova requires a good record of its rise and fall in brightness, or light curve. Although SN 2007bi was detected more than a week after its peak, Nugent delved into years of data compiled by NERSC from the SNfactory and other surveys. He found that the Catalina Sky Survey had recorded SN 2007bi before its peak brightness and could provide enough data to calculate the duration of the rising curve, an extraordinarily long 70 days -- more evidence for the pair-instability identification.

A fossil laboratory of the early Universe

"It's significant that the first unambiguous example of a pair-instability supernova was found in a dwarf galaxy," says Nugent. "These are incredibly small, very dim galaxies that contain few elements heavier than hydrogen and helium, so they are models of the early Universe."

Dwarf galaxies are ubiquitous but so faint and dim -- "they take only a few pixels on a camera," says Nugent, "and until recently, with the development of wide-field projects like the SNfactory, astronomers had wanted to fill the chip with galaxies" -- that they've rarely been studied. SN 2007bi is expected to focus attention on what Gal-Yam and his collaborators call "fossil laboratories to study the early Universe."

Says Filippenko, "In the future, we might end up detecting the very first generation of stars, early in the history of the Universe, through explosions such as that of SN 2007bi -- long before we have the capability of directly seeing the pre-explosion stars."

With the advent of the multi-institutional Palomar Transient Factory, a fully automated, wide-field survey to find transients, led by Caltech's Shri Kulkarni, and with the aid of the Deep Sky Survey established by Nugent at NERSC to compile historical data from Palomar-QUEST, the SNfactory, the Near Earth Asteroid Team, and other surveys, the collaborators expect they will soon find many more ultrabright, ultramassive supernovae, revealing the role of these supernovae in creating the Universe as we know it today.

Cassini's Big Sky: View from the Center of Our Solar System

2009-12-05T02:38:00.000-08:00

When NASA's Cassini spacecraft began orbiting Saturn five years ago, a dozen highly-tuned science instruments set to work surveying, sniffing, analyzing and scrutinizing the Saturnian system.

But Cassini recently revealed new data that appeared to overturn the decades-old belief that our solar system resembled a comet in shape as it moves through the interstellar medium (the matter between stars in our corner of the Milky Way galaxy).

Instead, the new results suggest our heliosphere more closely resembles a bubble -- or a rat -- being eaten by a boa constrictor: as the solar system passes through the "belly" of the snake, the ribs, which mimic the local interstellar magnetic field, expand and contract as the rat passes.

"At first I was incredulous," said Tom Krimigis, principal investigator of the Magnetospheric Imaging Instrument (MIMI) at Johns Hopkins University's Applied Physics Laboratory in Laurel, Md. "The first thing I thought was, 'What's wrong with our data?'"

Krimigis and his colleagues on the instrument team published the Cassini findings in the Nov. 13 issue of the journal Science, which featured complementary results from NASA's Interstellar Boundary Explorer (IBEX). Together, the results create the first map of the heliosphere and its thick outer layer known as the heliosheath, where solar wind streaming out from the sun gets heated and slowed as it interacts with the interstellar medium.

The Cassini data also provide a much more direct indication of the thickness of the heliosheath, whereas scientists previously had to rely on calculations from models. The new results from Cassini show that the heliosheath is about 40 to 50 astronomical units (3.7 billion to 4.7 billion miles) thick and that NASA's twin Voyager spacecraft, which are traveling through the heliosheath now, will cross into true interstellar space well before the year 2020. Estimates as far out as 2030 had been suggested.

"These new data from Cassini really redefine our sense of our home in the galaxy, and we can now do better studies of whether our solar system resembles those elsewhere," Krimigis said.

The Voyagers have sent back rich data on the heliosphere and heliosheath, but just at two locations. Scientists want more context. One way to learn about the region is to track energetic neutral atoms streaming back toward the sun from the heliosheath.

Energetic neutral atoms form when cold, neutral gas collides with electrically-charged particles in a cloud of plasma, which is a gas-like state of matter so hot that the atoms split into an ion and an electron. The positively-charged ions in plasma can't reclaim their own electrons, which are moving too fast, but they can steal an electron from the cold gas atoms. Since the resulting particles are neutrally charged, they are able to escape magnetic fields and zoom off into space. The emission of these particles often occurs in the magnetic fields surrounding planets, but also happens when the solar wind mingles with the interstellar medium.

How did Cassini, with 22,000 wire connections and 14 kilometers (8.7 miles) of cabling specifically tweaked to get the most out of its investigation of the solar system's second largest gas bag, recently end up helping to redefine how we look at our entire solar system?

Krimigis and his Cassini colleagues working with MIMI weren't sure their instrument could pick up emissions from far-out, exotic locations, such as from the boundary of our heliosphere, the region of our sun's influence.

Last year, after spending four years focused on the energetic electrons and ions trapped in the magnetic field that surrounds Saturn, as well as the offspring of these particles known as energetic neutral atoms, the team started combing through the data from the instrument's Ion and Neutral Camera, looking for particles arriving from far beyond Saturn.

"We thought we could get some hits from energetic neutral atoms from the heliosheath because Cassini has really been in an excellent position to detect these particles," said Don Mitchell, MIMI instrument scientist and a researcher at the Applied Physics Laboratory.

Cassini was farther away from the sun than previous spacecraft trying to image the heliosphere and even swung very far away from Saturn on some of its orbits, Mitchell said. The data would likely be free of much of the interference that hampered other efforts.

Mitchell, Krimigis and their team were able to stitch together data from late 2003 to the summer of 2009. They created a color-coded map of the intensity of the energetic neutral atoms and discovered a belt of hot, high-pressure particles where the interstellar wind flowed by our heliosheath bubble.

The data matched up nicely with the IBEX images of lower-energy particles and connected that data set to the Voyager data on higher-energy particles.

"I was initially skeptical because the instrument was designed for Saturn's magnetosphere," Mitchell said, "But our camera had long exposures of months to years, so we could accumulate and map each particle that streamed through the tiny aperture from the far reaches of the heliosphere. It was luck, but also a lot of hard work."

Antarctica Served as Climatic Refuge in Earth's Greatest Extinction Event

2009-12-04T05:41:00.000-08:00

The largest known mass extinction in Earth's history, about 252 million years ago at the end of the Permian Period, may have been caused by global warming. A new fossil species suggests that some land animals may have survived the end-Permian extinction by living in cooler climates in Antarctica. Jörg Fröbisch and Kenneth D. Angielczyk of The Field Museum together with Christian A. Sidor from the University of Washington have identified a distant relative of mammals, Kombuisia antarctica, that apparently survived the mass extinction by living in Antarctica.

The new species belongs to a larger group of extinct mammal relatives, called anomodonts, which were widespread and represented the dominant plant eaters of their time.

"Members of the group burrowed in the ground, walked the surface and lived in trees," said Fröbisch, the lead author of the study. "However,Kombuisia antarctica, about the size of a small house cat, was considerably different from today's mammals -- it likely laid eggs, didn't nurse its young and didn't have fur, and it is uncertain whether it was warm blooded," said Angielczyk, Assistant Curator of Paleomammology at The Field Museum. Kombuisia antarctica was not a direct ancestor of living mammals, but it was among the few lineages of animals that survived at a time when a majority of life forms perished.

Scientists are still debating what caused the end-Permian extinction, but it was likely associated with massive volcanic activity in Siberia that could have triggered global warming. When it served as refuge, Antarctica was located some distance north of its present location, was warmer and wasn't covered with permanent glaciers, said the researchers. The refuge of Kombuisia in Antarctica probably wasn't the result of a seasonal migration but rather a longer-term change that saw the animal's habitat shift southward. Fossil evidence suggests that small and medium sized animals were more successful at surviving the mass extinction than larger animals. They may have engaged in "sleep-or-hide" behaviors like hibernation, torpor and burrowing to survive in a difficult environment.

Earlier work by Fröbisch predicted that animals like Kombuisia antarctica should have existed at this time, based on fossils found in South Africa later in the Triassic Period that were relatives of the animals that lived in Antarctica. "The new discovery fills a gap in the fossil record and contributes to a better understanding of vertebrate survival during the end-Permian mass extinction from a geographic as well as an ecological point of view," Fröbisch said.

The team found the fossils of the new species among specimens collected more than three decades ago from Antarctica that are part of a collection at the American Museum of Natural History. "At the time those fossils were collected, paleontologists working in Antarctica focused on seeking evidence for the existence of a supercontinent, Pangaea, that later split apart to become separate land masses," said Angielczyk. The fossils collected in Antarctica provided some of the first evidence of Pangaea's existence, and further analysis of the fossils can refine our understanding of events that unfolded 250 million years ago.

"Finding fossils in the current harsh conditions of Antarctica is difficult, but worthwhile," said Angielczyk. "The recent establishment of the Robert A. Pritzker Center for Meteoritics and Polar Studies at The Field Museum recognizes the growing importance of the region," he said.

This research is part of a collaborative study of Dr. Jörg Fröbisch (Department of Geology, Field Museum, Chicago), Dr. Kenneth D. Angielczyk (Department of Geology, Field Museum, Chicago), and Dr. Christian A. Sidor (Burke Museum and Department of Biology, University of Washington), which will be published online December 3, 2009 inNaturwissenschaften.

First Direct Observation of a Planet-Like Object Orbiting Star Similar to Sun

2009-12-04T05:39:00.000-08:00

An international team of scientists that includes an astronomer from Princeton University has made the first direct observation of a planet-like object orbiting a star similar to the sun.

Brown dwarfs are stars that are not massive enough to sustain fusion reactions at their core, so they burn out and cool off as they age.

By Feeding the Birds, You Could Change Their Evolutionary Fate

2009-12-04T05:37:00.000-08:00

Feeding birds in winter is a most innocent human activity, but it can nonetheless have profound effects on the evolutionary future of a species, and those changes can be seen in the very near term. That's the conclusion of a report published online on December 3rd in Current Biology, showing that what was once a single population of birds known as blackcaps has been split into two reproductively isolated groups in fewer than 30 generations, despite the fact that they continue to breed side by side in the very same forests.

The reproductive isolation between these populations, which live together for part of the year, is now stronger than that of other blackcaps that are always separated from one another by distances of 800 kilometers or more, the researchers said.

"Our study documents the profound impact of human activities on the evolutionary trajectories of species," said Martin Schaefer of the University of Freiburg. "It shows that we are influencing the fate not only of rare and endangered species, but also of the common ones that surround our daily lives."

The split that the researchers observed followed the recent establishment of a migratory divide between southwest- and northwest-migrating blackcap (Sylvia atricapilla) populations in Central Europe after humans began offering food to them in the winter. The two groups began to follow distinct migratory routes -- wintering in Spain and the United Kingdom -- and faced distinct selective pressures. Under that pressure, the two groups have since become locally adapted ecotypes. (Ecotypes represent the initial step of differentiation among populations of the same species, the researchers explained. If ecotypes continue down that path, they can ultimately become separate species.)

"The new northwest migratory route is shorter, and those birds feed on food provided by humans instead of fruits as the birds that migrate southwest do," Schaefer said. "As a consequence, birds migrating northwest have rounder wings, which provide better maneuverability but make them less suited for long-distance migration." They also have longer, narrower bills that are less equipped for eating large fruits like olives during the winter.

Schaefer says it isn't clear whether the ecotypes will ever become separate species; in fact, he doubts they will because the habits of humans will tend to change over time. Even so, the findings do speak to the long-standing debate about whether geographic separation is necessary for speciation to occur. In particular, it had been contentious whether selection could act strongly and consistently enough in sympatry to separate a united gene pool.

"In highly mobile organisms such as birds, the consensus is that sympatric speciation is extremely rare, mainly because it is difficult to envisage how gene pools could be kept separate until speciation has occurred," Schaefer said. "Our results now show that the initial steps of speciation can occur very quickly in a highly mobile, migratory bird," because divergent selection during the overwintering phase leads to the evolution of reproductive isolation.

"This is a nice example of the speed of evolution," he added. "It is something that we can see with our own eyes if we only look closely enough. It doesn't have to take millions of years."

Global Warming Causes Outbreak Of Rare Algae Associated With Corals, Study Finds

2009-12-03T05:33:00.000-08:00

A rare opportunity has allowed a team of biologists to evaluate corals and the essential, photosynthetic algae that live inside their cells before, during, and after a period in 2005 when global warming caused sea-surface temperatures in the Caribbean Ocean to rise.

The team, led by Penn State Assistant Professor of Biology Todd LaJeunesse, found that a rare species of algae that is tolerant of stressful environmental conditions proliferated in corals as the more-sensitive algae were being expelled from corals. The results will be published in the online version of the journal Proceedings of the Royal Society B on 9 September 2009.

"Symbiodinium trenchi is normally a rare species of micro-alga in the Caribbean," said LaJeunesse. "Because the species is apparently tolerant of high or fluctuating temperatures, it was able to take advantage of the warming event and become more prolific. In this way, Symbiodinium trenchiappears to have saved certain colonies of coral from the damaging effects of unusually warm water. As ocean temperatures continue to rise as a result of global warming, we can expect this species to become more common and persistent. However, since it is not normally associated with corals in the Caribbean, we don't know if its increased presence will benefit or harm corals in the long term."

According to LaJeunesse, certain species of algae have evolved over millions of years to live in symbiotic relationships with certain species of corals. The photosynthetic algae provide the corals with nutrients and energy, while the corals provide the algae with nutrients and a place to live. "There is a fine balance between giving and taking in these symbiotic relationships," said LaJeunesse. "If Symbiodinium trenchi takes from the corals more than it gives back, then over time we will see the health of the corals diminish."

In 2005, sea surface temperatures in the Caribbean Ocean rose by up to two degrees Celsius above normal for a period of three to four months, high enough and long enough to severely stress the natural symbioses. This process of damaged or dying algae being expelled from the cells of corals is known as bleaching because it leaves behind bone-white coral skeletons that soon will die without their symbiotic partners.

During the summer of 2005, prior to the bleaching event, LaJeunesse and his colleagues collected samples of coral and algae from two locations near Barbados in the Caribbean. "We collected the samples as part of an effort to document the diversity of Symbiodinium species around the world and to study how relationships between certain species of corals and algae differ across geographic space," he said.

By late November, water temperatures had peaked and many corals were bleached. "Finding out about the bleaching event was bittersweet," said LaJeunesse. "It was upsetting to see how severe the impact was to the coral communities, but I also knew it would be a good opportunity to learn more about what happens to corals and their algal partners during times of acute stress. In fact, I knew that this would be one of the first times that anyone had had the opportunity to conduct a community-wide study of corals and algae before, during, and after a bleaching event."

The team collected samples of coral and algae during the bleaching event and again two years after ocean temperatures returned to normal. In the laboratory, they sequenced the organisms' DNA to identify the species.

"During the bleaching event, we found that Symbiodinium trenchi, which we rarely find in the Caribbean, had increased in frequency by 50 percent, or more, within coral species that are most sensitive to warm water. We also saw this species in corals where it had never been before. Two years later, we found that the abundance and occurrence of Symbiodinium trenchi had diminished significantly," said LaJeunesse. Today, the symbioses have mostly recovered to their normal state, and the corals have been repopulated by their typical algal symbionts," he said.

Although Symbiodinium trenchi appears to have saved some Barbadian corals from possibly dying in 2005, LaJeunesse is concerned that the species might not be good for the corals in the long term in the event that warming trends continue andSymbiodinium trenchi becomes more common. "BecauseSymbiodinium trenchi does not appear to have successfully co-evolved with Caribbean coral species, it may not provide the corals with adequate nutrition," he said.

In the future, LaJeunesse plans to further investigate the relationships among Symbiodinium trenchi and Caribbean coral species. "We're interested in looking at how Symbiodinium trenchi behaves in other regions of the world where it is naturally common. We also want to look more closely at the give-and-take relationship between Symbiodinium trenchi and corals in the Caribbean

Marine Life Collected to Inventory DNA Sequence of All Pacific Island's Living Species

2009-12-03T05:32:00.000-08:00

University of Florida researchers are collecting marine invertebrates on the French Polynesian island of Moorea as part of a massive effort to inventory the DNA sequence of every living species there.

The genetic information collected by scientists from UF's Florida Museum of Natural History is part of a whole-system approach that will be used to study ecological processes in depth across the entire island. Moorea's coral reefs in particular are considered crucial indicators of how natural systems respond to climate change.

"Nobody has ever sequenced a single place to this level," said Gustav Paulay, the project's team leader for marine invertebrates and the Florida Museum's curator of marine malacology. "And nobody has ever investigated coral reef biodiversity this thoroughly in one place."

The three-year Moorea Biocode Project is now in its second year. Several Florida Museum researchers are in the field using scuba gear, snorkels and wading nets to collect specimens for the first-of-its-kind project.

The Florida Museum scientists are one of seven teams collecting specimens on everything from terrestrial vertebrates to algae. Marine invertebrates make up about 50 percent of the species on the island, which is about 37 miles in circumference and 11 miles from Tahiti.

Based at the UC Berkeley Richard B. Gump South Pacific Research Station on Moorea, the UF team collects specimens up to three times a day. The catch includes crabs, shrimp, plankton, mollusks and worms.

Back at the research station lab, the larger specimens are grouped by appearance. The researchers select individual specimens from each grouping to photograph and take tissue samples. The samples are sent to an on-site DNA extractor for immediate preparation, and the DNA is shipped to the Smithsonian Institution for sequencing.

"We can answer all these things in ecology and evolution and resource management if we have a dictionary to the DNA," Paulay said. "We're building that dictionary."

Attempting to collect all species of marine invertebrates is a daunting task. To meet the challenge, Paulay's team divides the works into three sizes: macro (anything longer than four-tenths of an inch), meso (smaller but visible) and micro (less than 1 mm in length).

Paulay hopes to effectively cover the macro fauna, but even that is impossible, he said. Rare things live in strange places. Other things migrate into the area every couple of years. Meso-organisms are even more difficult. Paulay's team uses a number of extractive methods, such as shaking them out of sand and rock, to get as many unique specimens as possible.

Microfauna are the most challenging of all. The coral reefs are full of them, like microscopic plankton in sea water and minute worms in sand and rock. Paulay's team is exploring methods of community DNA extraction. This approach involves running a simultaneous DNA analysis on all organisms found in a sample such as sand. Cluster patterns in the DNA sequences will help indicate individual species. Modern technology can sequence millions of genes at once, making the technique possible.

Larger invertebrates are easier to find, but they still provide plenty of surprises.

"You're always expecting to see things you haven't seen before," Paulay said. "Just about every day there's some really weird thing coming in."

Paulay estimates more than 5 percent of the macrofauna his team collects are new genera and species. The team recently found a new species of crab in deep water that looks like a transition species between a hermit crab and a free-moving crab. It wears a clam shell instead of a snail shell, and its main body has a crab-like triangular shape.

"I knew enough about hermit crabs to know this was pretty special, "Paulay said. "So I e-mailed a picture of it to a specialist and got an answer back the next day."

Having such a vast store of genetic information for Moorea is also bound to attract a lot of additional research, Paulay said. The island's coral reefs are being studied under a long-term ecological research project funded by the National Science Foundation. And DNA information from the Moorea project is being uploaded to a global sequencing effort known as the Barcode of Life, which hopes to collect a DNA sequence for every living thing on the planet.

Coral Reefs Inspire Rare Consensus Just Save Them

2009-12-03T05:31:00.000-08:00

One of the first set of studies to examine what tourists and recreation enthusiasts actually think about coral reef ecosystems suggests they are a rare exception to controversies over human use versus environmental conservation -- their stunning beauty is so extraordinary that almost everyone wants them protected in perpetuity.

That core belief is often strong enough that if it means people have to be kept out, so be it.

The analysis, done in Hawaii by researchers from Oregon State University and the University of Hawaii, found that most people visiting the state's coral reef ecosystems care deeply about these areas and very much enjoy visiting them, but will generally endorse whatever amount of management is needed to protect them.

"It was really quite astonishing, almost shocking how much people wanted this resource protected for its own sake," said Mark Needham, an assistant professor of forest ecosystems and society at OSU. "We fish and hunt wildlife for food or sport, we cut trees for timber. In most natural resource issues, we find conflicts over management for economic value versus environmental preservation or protection, but we really didn't see that here.

"Our surveys found overwhelmingly that people visiting coral reef areas did not think that human use and access were the most important issues when it came to these areas," he said. "And if anything was to have a deleterious effect on reef ecosystems, they would want it stopped."

That attitude was also of interest, Needham said, because in Hawaii coral reef ecosystems are a major draw for the tourism industry -- seven million people a year who spend more than $11 billion, in part, to enjoy the glistening waters, multi-colored corals, and myriad tropical fish. They are a destination for everyone from snorkelers and scuba divers to tourists in glass-bottom boats and toddlers wading knee-deep, all who come to see the incredible diversity of marine life. More than 80 percent of Hawaii's visitors recreate in the state's coastal and marine areas, and a majority go snorkeling or diving.

Past research has been done in many places around the world to analyze physical damage or other pressures placed on coral reefs, which in some cases has resulted in steps to reduce human use or educate visitors on reef protection. But until now, resource managers had no real barometer on just how much public support there was for such measures, especially among hobbyists and tourists who use this resource.

These recent surveys obtained attitudes and opinions from more than 3,500 residents and tourists visiting seven coral reef sites in the Hawaiian Islands, including state marine protected areas, fisheries management areas, and a county beach park. The surveys also measured attitudes about overuse and crowding, and opinions about management needs.

Opinions about coral reefs varied, Needham said, but were mostly just variations on how much protection might be needed, with some people feeling more extreme than others. Virtually no one wanted expanded use of coral reefs to the extent it might degrade them for enjoyment by future generations, and many were willing to endorse any level of protection needed, even if it meant banning human use. These views toward coral reefs reflected peoples' core personal values and are unlikely to change much, scientists said.

The studies showed that acceptance of potential future management strategies would be driven largely by perceived health of coral reefs and changes to these ecosystems.

"Litter, facilities, and crowding were not as important as coral reef conditions in influencing support or opposition to management actions such as limiting human use and increasing public information," Needham said. "This is surprising because in many parks and protected areas on land, social issues such as crowding and litter heavily influence attitudes toward management.

"In a marine context," he added, "it appears that environmental conditions may be more important."

More education and interpretation was commonly sought to help address issues of concern, such as people damaging corals by standing on them, the report found. The studies were supported by the Hawaii Coral Reef Initiative and State of Hawaii Division of Aquatic Resources. Some results of this work have been accepted for publication in professional journals.

This research should be considered good news for managers seeking support for their marine protection and conservation efforts, Needham said.

However, further studies are needed in other states and countries and with other segments of the public, he said, including some that have a much stronger orientation toward managed use instead of recreation or environmental protection. Needham is now working with Brian Szuster, an assistant professor of geography at the University of Hawaii, to examine this topic in other areas of Hawaii and in other countries.

Marine Lab Team Seeks To Understand Coral Bleaching

2009-12-03T05:30:00.001-08:00

With technology similar to that used by physicians to perform magnetic resonance imaging (MRI) scans, researchers from six institutions -- including the National Institute of Standards and Technology (NIST) -- working at the Hollings Marine Laboratory (HML) in Charleston, S.C., are studying the metabolic activity of a pathogen shown to cause coral bleaching, a serious threat to undersea reef ecosystems worldwide.

Coral bleaching is the whitening of living coral due to a disruption of the symbiosis (two organisms whose living together benefits both) with its zooxanthellae, tiny photosynthesizing algae. These unicellular creatures reside within the coral's tissues and provide the host organism with up to 90 percent of its energy. It's the solar-derived chemical products of these algae that give the world's coral species a rainbow of vivid colors. Unfortunately, ecologically valuable coral colonies around the globe are being threatened by an ocean-dwelling bacterium known as Vibrio coralliilyticus. When the microbe becomes virulent, it can infiltrate coral and dislodge the zooxanthellae, causing the coral to lose its pigmentation. If symbiosis is disrupted long enough, the coral dies from starvation.

Environmental scientists have shown in laboratory experiments that the virulence of V. coralliilyticus is temperature dependent, causing bleaching at temperatures above 24 degrees Celsius (75 degrees Fahrenheit). These findings have raised concerns that increasing ocean temperatures -- either through natural seasonal changes or climate change trends -- may lead to increased risk of widespread coral bleaching. During the past two decades, it has been reported that nearly 30 percent of the world's coral reefs -- and the ecosystems they support -- have been severely degraded by bleaching.

In a recent paper in Environmental Science and Technology, the HML research team described how it used nuclear magnetic resonance (NMR) to study metabolic changes in V. coralliilyticus resulting from temperature effects. The technique allows discovery of small-molecule metabolism-related compounds that correlate with different biological conditions. In this study, the levels of three compounds -- betaine, glutamate and succinate -- that help regulate energy production and osmotic pressure (a mechanism for maintaining cellular integrity) in V. coralliilyticus were determined to vary significantly between 24 degrees Celsius when the bacterium is not virulent and 27 degrees Celsius (81 degrees Fahrenheit) when it is. These metabolic changes, the HML team believes, are clues to learning why the small temperature change can turn non-virulent V. coralliilyticus into a coral bleaching menace.

Future metabolomic studies of V. coralliilyticus are planned to better understand the complete temperature-dependent mechanism involved in its pathogenicity. The researchers hope that these findings will lead to a better understanding of the symbiotic relationships that exist in healthy coral and the potential impacts on those relationships under changing ecological conditions.

Resonating Feathers Produce Courtship Song in Rare Bird

2009-12-02T05:30:00.000-08:00

Four years ago, a Cornell researcher reported a bizarre example of sexual selection in a rare South American bird: The male attracts the female by rubbing specialized wing feathers -- more than 100 cycles per second -- to create a high hum, similar to a sustained violin note.

While the researchers speculated how the sound was created, they have since proven that the club-winged manakin's feathers resonate at a particular frequency to create the tone.

The adaptation is a striking example of a species modifying an essential body part for the purpose of attracting a mate.

"We normally don't think of sexual selection transforming areas of critical importance," said Kim Bostwick, curator of Cornell Museum of Vertebrates and lead author of a study published in the Nov. 11 issue of the Proceedings of the Royal Society.

The sparrow-sized, club-winged manakin has nine inner-wing feathers held adjacent by a ligament on each wing, but uniquely, the two innermost feathers, called the "sixth and seventh secondaries," have enlarged and hollow shafts. The researchers found that when the enlarged sixth and seventh feathers are excited at their resonant frequency -- an object's natural frequency of vibration -- all nine hollow feathers resonate as a unit at 1500 Hertz to create the violinlike note close to an F-sharp. The wing also produces a second harmonic tone at a similar or greater volume as the fundamental tone.

"These feathers have turned into a kind of tuning fork," Bostwick said.

The researchers discovered that all feathers naturally resonate at a frequency of 1500 Hz, but this weak resonance cannot be heard without such special adaptations as the enlarged hollow feathers of the male club-winged manakin, which create the audible tone that attracts females. "The beginnings of that resonance already existed in the feathers," Bostwick said.

Co-authors include Damian Elias, Ph.D. '06, now an assistant professor at the University of California-Berkeley, and Andrew Mason, a former Cornell postdoctoral researcher, now an assistant professor at University of Toronto.

The study was supported by the National Science Foundation and the National Institutes of Health.

CSI Sharks: New Forensic Technique Gives Clues About Sharks from Bite Damage

2009-12-02T05:28:00.001-08:00

Hit-and-run attacks by sharks can be solved with a new technique that identifies the culprits by the unique chomp they put on their victims, according to a University of Florida researcher and shark expert.

In a method analogous to analyzing human fingerprints, scientists can make identifications by precisely comparing shark bites to the jaws and teeth of the powerful predators, said George Burgess, director of the International Shark Attack File, which is housed at UF's Florida Museum of Natural History.

"Every time we investigate a shark attack one of the pieces of information that we want to have is what species was involved and what size it was," he said. "Because I've been looking at shark attack victims for 30 years I can estimate what did the damage, but I have never been able to actually prove it."

Now scientists can say with a degree of certainty whether the beast was a 14-foot tiger shark or a 9-foot bull shark, a distinction that has unforeseen emotional, ecological and even monetary benefits, said Burgess, who collaborated with researchers from the University of South Florida. Their findings are published in the November issue of Marine Biology.

"There's a psychological need for many shark attack victims to know what bit them," Burgess said. "One of the few things shark attack victims have going for them after a bite is bragging rights and the bragging rights include knowing what did the damage."

Because of the hype surrounding shark attacks, off-the-cuff estimates of shark size are often exaggerated, he said. "This will give an actual basis for determining what species was involved and the size, not that that's going to affect the size claimed by the victim in a bar," he said.

Using dried shark jaws from museums and private collections, the researchers were able to identify bite patterns of particular sizes and species of sharks by measuring jaw circumference and the distance between the six frontal teeth on the top and lower jaws, Burgess said. They experimented on 10 to 24 sets of shark jaws for each of the 14 species they analyzed. The technique works not only on human and animal tissue, but also on inanimate objects like surfboards and underground cable lines, he said.

The ability to make predictions from bite patterns is important to understanding the behavioral underpinnings of shark attacks and their prey habits, said lead researcher Dayv Lowry, a biologist with the Washington Department of Fish and Wildlife, who did the work as a graduate student at the University of South Florida.

"Often someone will send us a picture of a dolphin carcass or a sea turtle and want to know what kind of shark bit it," Lowry said. "Knowing that it's a large tiger shark, for example, would help us figure out what large tiger sharks like to eat and how they attack their prey. If an animal or person has been bitten on the rear end, then we know these sharks are likely to sneak up to get their prey instead of facing the victims."

Being able to determine what size shark attacked people in certain geographic areas such as South Africa where offshore nets are used to protect swimmers is valuable because it may influence the size mesh that is used, Lowry said. With larger sharks, beaches can get by with bigger mesh sizes, which are cheaper and less environmentally intrusive, he said.

The technique also has the potential to save thousands of dollars in damages caused by the sharks' penchant for attacking underwater electronic equipment, which includes intercontinental telephone wires, top-secret communication lines between government officials and sensors companies use to uncover oil fields, Burgess said.

Sharks are equipped with organs on the underside of their snouts -- gel filled pits called ampullae of Lorenzini -- that allow them to detect electromagnetic fields from their intended food, Burgess said. Unfortunately, sharks often do not distinguish between the signals sent by prey and equipment, which can be ruined by water seeping in through the bite marks, he said.

"That's one thing that makes them special -- they can sense electro-magnetic fields around their prey items," he said.

Laying cable lines at the bottom of the ocean is extremely expensive, and having to remove a piece, fix it and install it again adds to the cost, Burgess said. "Knowing that a certain species of shark did the damage is useful because in the future cable lines can be placed in a different location, outside the path of that particular shark's area of distribution," he said.

And the ability to determine what size shark was involved in an attack by the size and configuration of its bite marks could result in the installation of a heavier seal designed to withstand damage from that kind of shark, he said.

Increased Ocean Acidification In Alaska Waters, New Findings Show

2009-12-02T05:25:00.000-08:00

The same things that make Alaska's marine waters among the most productive in the world may also make them the most vulnerable to ocean acidification. According to new findings by a University of Alaska Fairbanks scientist, Alaska's oceans are becoming increasingly acidic, which could damage Alaska's king crab and salmon fisheries.

The pteropod (also known as a sea butterfly or swimming sea snail) may be one of the first marine organisms affected by ocean acidification. Pteropods make up nearly half of the pink salmon diet.

This spring, chemical oceanographer Jeremy Mathis returned from a cruise armed with seawater samples collected from the depths of the Gulf of Alaska. When he tested the samples' acidity in his lab, the results were higher than expected. They show that ocean acidification is likely more severe and is happening more rapidly in Alaska than in tropical waters. The results also matched his recent findings in the Chukchi and Bering Seas.

"It seems like everywhere we look in Alaska's coastal oceans, we see signs of increased ocean acidification," said Mathis.

Often referred to as the "sister problem to climate change," ocean acidification is a term to describe increasing acidity in the world's oceans. The ocean absorbs carbon dioxide from the air. As the ocean absorbs more carbon dioxide, seawater becomes more acidic. Scientists estimate that the ocean is 25 percent more acidic today than it was 300 years ago.

"The increasing acidification of Alaska waters could have a destructive effect on all of our commercial fisheries. This is a problem that we have to think about in terms of the next decade instead of the next century," said Mathis.

The ocean contains minerals that organisms like oysters and crabs use to build their shells. Ocean acidification makes it more difficult to build shells, and in some cases the water can become acidic enough to break down existing shells. Mathis' recent research in the Gulf of Alaska uncovered multiple sites where the concentrations of shell-building minerals were so low that shellfish and other organisms in the region would be unable to build strong shells.

"We're not saying that crab shells are going to start dissolving, but these organisms have adapted their physiology to a certain range of acidity. Early results have shown that when some species of crabs and fish are exposed to more acidic water, certain stress hormones increase and their metabolism slows down. If they are spending energy responding to acidity changes, then that energy is diverted away from growth, foraging and reproduction," said Mathis.

Another organism that could be affected by ocean acidification is the tiny pteropod, also known as a sea butterfly or swimming sea snail. The pteropod is at the base of the food chain and makes up nearly half of the pink salmon's diet. A 10 percent decrease in the population of pteropods could mean a 20 percent decrease in an adult salmon's body weight.

"This is a case where we see ocean acidification having an indirect effect on a commercially viable species by reducing its food supply," said Mathis.

The cold waters and broad, shallow continental shelves around Alaska's coast could be accelerating the process of ocean acidification in the North, Mathis said. Cold water can hold more gas than warmer water, which means that the frigid waters off Alaska's coasts can absorb more carbon dioxide. The shallow waters of Alaska's continental shelves also retain more carbon dioxide because there is less mixing of seawater from deeper ocean waters.

Ask any coastal Alaskan and they will tell you that Alaska's waters are teeming with biological life, from tiny plankton to humpback whales. All of these animals use oxygen and emit carbon dioxide. Mathis and other scientists call this the "biological pump."

"We are blessed with highly productive coastal areas that support vast commercial fisheries, but this productivity acts like a pump, absorbing more and more carbon dioxide from the atmosphere," said Mathis. "Because of this, the acidity of Alaska's coastal seas will continue to increase, and likely accelerate, over the next decade."

Mathis said that it is still unclear what the full range of effects of ocean acidification will be, but that it is a clear threat to Alaska's commercial fisheries and subsistence communities.

"We need to give our policy makers and industry managers information and forecasts on ocean acidification in Alaska so they can make decisions that will keep our fisheries viable," said Mathis. "Ecosystems in Alaska are going to take a hit from ocean acidification. Right now, we don't know how they are going to respond."

Ocean Growing More Acidic Faster Than Once Thought; Increasing Acidity Threatens Sea Life

2009-12-02T05:21:00.000-08:00

University of Chicago scientists have documented that the ocean is growing more acidic faster than previously thought. In addition, they have found that the increasing acidity correlates with increasing levels of atmospheric carbon dioxide, according to a paper published online by the Proceedings of the National Academy of Sciences on Nov. 24.

"Of the variables the study examined that are linked to changes in ocean acidity, only atmospheric carbon dioxide exhibited a corresponding steady change," said J. Timothy Wootton, the lead author of the study and Professor of Ecology and Evolution at the University of Chicago.

The increasingly acidic water harms certain sea animals and could reduce the ocean's ability to absorb carbon dioxide, the authors said. Scientists have long predicted that higher levels of atmospheric carbon dioxide would make the ocean more acidic. Nevertheless, empirical evidence of growing acidity has been limited.

The new study is based on 24,519 measurements of ocean pH spanning eight years, which represents the first detailed dataset on variations of coastal pH at a temperate latitude—where the world's most productive fisheries live.

"The acidity increased more than 10 times faster than had been predicted by climate change models and other studies," Wootton said. "This increase will have a severe impact on marine food webs and suggests that ocean acidification may be a more urgent issue than previously thought, at least in some areas of the ocean."

The ocean plays a significant role in global carbon cycles. When atmospheric carbon dioxide dissolves in water it forms carbonic acid, increasing the acidity of the ocean. During the day, carbon dioxide levels in the ocean fall because photosynthesis takes it out of the water, but at night, levels increase again. The study documented this daily pattern, as well as a steady increase in acidity over time.

"Many sea creatures have shells or skeletons made of calcium carbonate, which the acid can dissolve," said Catherine Pfister, Associate Professor of Ecology and Evolution at the University of Chicago and a co-author of the study. "Therefore, the increased acidity of the ocean could interfere with many critical ocean processes such as coral reef building or shellfish harvesting."

Conducted at Tatoosh Island in the Pacific Ocean off the coast of Washington, the study documented that the number of mussels and stalked barnacles fell as acidity increased. At the same time, populations of smaller, shelled species and noncalcareous algae increased.

"Models revealed strong links between the dynamics of species living on the shore and variation in ocean pH," Wootton said. "The models project substantial shifts in the species dominating the habitat as a consequence of both the direct effects of reduced calcification and indirect effects arising from the web of species interactions."

The study, "Dynamical Patterns and Ecological Impacts of Declining Ocean pH in a High-Resolution Multi-Year Dataset," will be published in the Dec. 2 issue of PNAS. The third co-author, James Forester, was at the University of Chicago's Department of Ecology and Evolution but is currently at Harvard University.

"To date there is a lack of information about how the ocean carbon cycle has changed in recent years," Pfister said. "Atmospheric carbon dioxide concentrations will continue to increase, and our work points to the urgent need to better understand the ocean pH changes that this is likely to drive as well as how these changes will affect marine life."

In Carbon Dioxide-Rich Environment, Some Ocean Dwellers Increase Shell Production

2009-12-02T05:19:00.000-08:00

In a striking finding that raises new questions about carbon dioxide's (CO₂) impact on marine life, Woods Hole Oceanographic Institution (WHOI) scientists report that some shell-building creatures -- such as crabs, shrimp and lobsters -- unexpectedly build more shell when exposed to ocean acidification caused by elevated levels of atmospheric carbon dioxide (CO₂).

Because excess CO₂ dissolves in the ocean -- causing it to "acidify" -- researchers have been concerned about the ability of certain organisms to maintain the strength of their shells. Carbon dioxide is known to trigger a process that reduces the abundance of carbonate ions in seawater -- one of the primary materials that marine organisms use to build their calcium carbonate shells and skeletons.

The concern is that this process will trigger a weakening and decline in the shells of some species and, in the long term, upset the balance of the ocean ecosystem.

But in a study published in the Dec. 1 issue of Geology, a team led by former WHOI postdoctoral researcher Justin B. Ries found that seven of the 18 shelled species they observed actually built more shell when exposed to varying levels of increased acidification. This may be because the total amount of dissolved inorganic carbon available to them is actually increased when the ocean becomes more acidic, even though the concentration of carbonate ions is decreased.

"Most likely the organisms that responded positively were somehow able to manipulate…dissolved inorganic carbon in the fluid from which they precipitated their skeleton in a way that was beneficial to them," said Ries, now an assistant professor in marine sciences at the University of North Carolina. "They were somehow able to manipulate CO₂…to build their skeletons."

Organisms displaying such improvement also included calcifying red and green algae, limpets and temperate urchins. Mussels showed no effect.

"We were surprised that some organisms didn't behave in the way we expected under elevated CO₂," said Anne L. Cohen, a research specialist at WHOI and one of the study's co-authors. "What was really interesting was that some of the creatures, the coral, the hard clam and the lobster, for example, didn't seem to care about CO₂ until it was higher than about 1,000 parts per million [ppm]." Current atmospheric CO₂ levels are about 380 ppm, she said. Above this level, calcification was reduced in the coral and the hard clam, but elevated in the lobster

The "take-home message, " says Cohen, is that "we can't assume that elevated CO₂ causes a proportionate decline in calcification of all calcifying organisms." WHOI and the National Science Foundation funded the work.

Conversely, some organisms -- such as the soft clam and the oyster -- showed a clear reduction in calcification in proportion to increases in CO₂. In the most extreme finding, Ries, Cohen and WHOI Associate Scientist Daniel C. McCorkle exposed creatures to CO₂ levels more than seven times the current level.

This led to the dissolving of aragonite -- the form of calcium carbonate produced by corals and some other marine calcifiers. Under such exposure, hard and soft clams, conchs, periwinkles, whelks and tropical urchins began to lose their shells. "If this dissolution process continued for sufficient time, then these organisms could lose their shell completely," he said, "rendering them defenseless to predators."

"Some organisms were very sensitive," Cohen said, "some that have commercial value. But there were a couple that didn't respond to CO₂ or didn't respond till it was sky-high -- about 2,800 parts per million. We're not expecting to see that [CO₂level] anytime soon."

The researchers caution, however, that the findings -- and acidification's overall impact -- may be more complex than it appears. For example, Cohen says that available food and nutrients such as nitrates, phosphates and iron may help dictate how some organisms respond to carbon dioxide.

"We know that nutrients can be very important," she says. "We have found that corals for example, that have plenty of food and nutrients can be less sensitive" to CO₂. "In this study, the organisms were well fed and we didn't constrain the nutrient levels.

"I wouldn't make any predictions based on these results. What these results indicate to us is that the organism response to elevated CO₂ levels is complex and we now need to go back and study each organism in detail."

Ries concurs that any possible ramifications are complex. For example, the crab exhibited improved shell-building capacity, and its prey, the clams, showed reduced calcification. "This may initially suggest that crabs could benefit from this shift in predator-pray dynamics. But without shells, clams may not be able to sustain their populations, and this could ultimately impact crabs in a negative way, as well," Ries said.

In addition, Cohen adds, even though some organisms such as crabs and lobsters appear to benefit under elevated CO₂conditions, the energy they expend in shell building under these conditions "might divert from other important processes such as reproduction or tissue building."

Since the industrial revolution, Ries noted, atmospheric carbon dioxide levels have increased from 280 to nearly 400 ppm. Climate models predict levels of 600 ppm in 100 years, and 900 ppm in 200 years.

"The oceans absorb much of the CO₂ that we release to the atmosphere," Ries says. However, he warns that this natural buffer may ultimately come at a great cost.

"It's hard to predict the overall net effect on benthic marine ecosystems, he says. "In the short term, I would guess that the net effect will be negative. In the long term, ecosystems could re-stabilize at a new steady state.

"The bottom line is that we really need to bring down CO₂levels in the atmosphere."

Greening of Sahara Desert Triggered Early Human Migrations out of Africa

2009-11-30T22:42:00.000-08:00

A team of scientists from the NIOZ Royal Netherlands Institute for Sea Research and the University of Bremen (Germany) has determined that a major change in the climate of the Sahara and Sahel region of North Africa facilitated early human migrations from the African continent. The team's findings will be published online in the Nov. 9th installment of Early Edition of the Proceedings of the National Academy of Sciences USA. Among the key findings are that the Sahara desert and the Sahel were considerably wetter around 9,000, 50,000 and 120,000 years ago than at present, allowing for the growth of trees instead of grasses.

Dust in marine sediment cores

The researchers studied marine sediments covering nearly 200,000 years collected from the seafloor off the coast of Guinea in West Africa. Strong off-shore winds transport large volumes of dust from the Sahara and Sahel to the study area. Mixed in with the dust are plant leaf waxes, which are blown long distances across the African continent to the Atlantic Ocean, where they were ultimately deposited on the seafloor at about 3 km depth.

Over thousands of years, layers of sediment accumulated on the seafloor, each layer containing evidence of past environmental conditions in Northern Africa. The plant leaf waxes are resistant to degradation and when trapped within layers of sediment, they can be very well-preserved for millions of years.

Vegetation changes in the Sahara

Based on analysis of plant leaf waxes the researchers could determine the relative importance of trees and grasses in the Sahara and Sahel regions. Trees generally require more water to survive than do tropical grasses, and so by analysing the plant leaf waxes to determine if they were produced by trees or grasses, the scientists could examine past precipitation changes in tropical Africa over the last 200,000 years.

During three discrete periods, ca. 120,000-110,000 years, 50,000- 45,000 and 10,000-8,000 years ago, substantially more trees grew in Sahara and the Sahel, indicating significantly wetter conditions than at present. The two oldest periods exactly coincide with times when the earliest humans were migrating out of East Africa to northern Africa, the Middle East, Asia and eventually Europe. At these times, the wetter conditions in central North Africa likely enabled humans to cross this normally inhospitable region, allowing them to migrate into other continents. When climate in the Sahara and Sahel turned dry again, humans were forced out of these areas causing genetic and cultural changes in already inhabited regions such as Northern Africa and the Middle East.

Changes in ocean circulation caused a wetter Sahara

The researchers also looked for the causes of these major climate shifts to much wetter conditions in the Sahara and found that they were indirectly related to an increase in the strength of the major current system, the Atlantic Overturning Circulation (AOC). The researchers could assess the strength of this current by analysing fossilized tiny shells of small animals (benthic foraminifera).When the intensity of the AOC changes, this leads to changes in the chemical composition of the deep water masses, which is then reflected in the shells ofbenthic foraminifera. The researchers found that when the AOC weakened, more grasses were present in central North Africa indicating a drier climate. Likely, the weakening of the AOC was caused by increased freshwater input to the high-latitudes, leading to less saline surface waters. This freshwater input also caused surface cooling in these regions, in turn leading to movement of cold air from the high-latitudes to the tropics, and causing drier conditions in central North Africa.

Thus, early human migrations from the African continent were likely triggered by events originating far away in the North Atlantic.

This research project was funded by the Netherlands Organisation for Scientific Research (NWO) and the Deutsche Forschungsgemeinschaft Research Centre/Excellence Cluster "The Ocean in the Earth System".

Big Freeze Plunged Europe Into Ice Age in Months

2009-11-30T22:41:00.000-08:00

In the film The Day After Tomorrow, the world enters the icy grip of a new glacial period within the space of just a few weeks. Now new research shows that this scenario may not be so far from the truth after all.

William Patterson, from the University of Saskatchewan in Canada, and his colleagues have shown that switching off the North Atlantic circulation can force the Northern hemisphere into a mini 'ice age' in a matter of months. Previous work has indicated that this process would take tens of years.

Around 12,800 years ago the northern hemisphere was hit by a mini ice-age, known by scientists as the Younger Dryas, and nicknamed the 'Big Freeze', which lasted around 1300 years. Geological evidence shows that the Big Freeze was brought about by a sudden influx of freshwater, when the glacial Lake Agassiz in North America burst its banks and poured into the North Atlantic and Arctic Oceans. This vast pulse, a greater volume than all of North America's Great Lakes combined, diluted the North Atlantic conveyor belt and brought it to a halt.

Without the warming influence of this ocean circulation temperatures across the Northern hemisphere plummeted, ice sheets grew and human civilisation fell apart.

Previous evidence from Greenland ice cores has indicated that this sudden change in climate occurred over the space of a decade or so. Now new data shows that the change was amazingly abrupt, taking place over the course of a few months, or a year or two at most.

Patterson and his colleagues have created the highest resolution record of the 'Big Freeze' event to date, from a mud core taken from an ancient lake, Lough Monreach, in Ireland. Using a scalpel layers were sliced from the core, just 0.5mm thick, representing a time period of one to three months.

Carbon isotopes in each slice reveal how productive the lake was, while oxygen isotopes give a picture of temperature and rainfall. At the start of the 'Big Freeze' their new record shows that temperatures plummeted and lake productivity stopped over the course of just a few years. "It would be like taking Ireland today and moving it up to Svalbard, creating icy conditions in a very short period of time," says Patterson, who presented the findings at the European Science Foundation BOREAS conference on humans in the Arctic, in Rovaniemi, Finland.

Meanwhile, their isotope record from the end of the Big Freeze shows that it took around two centuries for the lake and climate to recover, rather than the abrupt decade or so that ice cores indicate. "This makes sense because it would take time for the ocean and atmospheric circulation to turn on again," says Patterson.

Looking ahead to the future Patterson says there is no reason why a 'Big Freeze' shouldn't happen again. "If the Greenland ice sheet melted suddenly it would be catastrophic," he says.

This study was part of a broad network of 38 individual research teams from Europe, Russia, Canada and the USA forming the European Science Foundation EUROCORES programme 'Histories from the North -- environments, movements, narratives' (BOREAS). This highly interdisciplinary initiative brought together scientists from a wide range of disciplines including humanities, social, medical, environmental and climate sciences.

Black Hole Caught Zapping Galaxy Into Existence?

2009-11-30T22:39:00.000-08:00

Which come first, the supermassive black holes that frantically devour matter or the enormous galaxies where they reside? A brand new scenario has emerged from a recent set of outstanding observations of a black hole without a home: black holes may be "building" their own host galaxy. This could be the long-sought missing link to understanding why the masses of black holes are larger in galaxies that contain more stars.

"The 'chicken and egg' question of whether a galaxy or its black hole comes first is one of the most debated subjects in astrophysics today," says lead author David Elbaz. "Our study suggests that supermassive black holes can trigger the formation of stars, thus 'building' their own host galaxies. This link could also explain why galaxies hosting larger black holes have more stars."

To reach such an extraordinary conclusion, the team of astronomers conducted extensive observations of a peculiar object, the nearby quasar HE0450-2958 (see ESO PR 23/05 for a previous study of this object), which is the only one for which a host galaxy has not yet been detected [1]. HE0450-2958 is located some 5 billion light-years away.

Until now, it was speculated that the quasar's host galaxy was hidden behind large amounts of dust, and so the astronomers used a mid-infrared instrument on ESO's Very Large Telescope for the observations [2]. At such wavelengths, dust clouds shine very brightly, and are readily detected. "Observing at these wavelengths would allow us to trace dust that might hide the host galaxy," says Knud Jahnke, who led the observations performed at the VLT. "However, we did not find any. Instead we discovered that an apparently unrelated galaxy in the quasar's immediate neighbourhood is producing stars at a frantic rate."

These observations have provided a surprising new take on the system. While no trace of stars is revealed around the black hole, its companion galaxy is extremely rich in bright and very young stars. It is forming stars at a rate equivalent to about 350 Suns per year, one hundred times more than rates for typical galaxies in the local Universe.

Earlier observations had shown that the companion galaxy is, in fact, under fire: the quasar is spewing a jet of highly energetic particles towards its companion, accompanied by a stream of fast-moving gas. The injection of matter and energy into the galaxy indicates that the quasar itself might be inducing the formation of stars and thereby creating its own host galaxy; in such a scenario, galaxies would have evolved from clouds of gas hit by the energetic jets emerging from quasars.

"The two objects are bound to merge in the future: the quasar is moving at a speed of only a few tens of thousands of km/h with respect to the companion galaxy and their separation is only about 22 000 light-years," says Elbaz. "Although the quasar is still 'naked', it will eventually be 'dressed' when it merges with its star-rich companion. It will then finally reside inside a host galaxy like all other quasars."

Hence, the team have identified black hole jets as a possible driver of galaxy formation, which may also represent the long-sought missing link to understanding why the mass of black holes is larger in galaxies that contain more stars [3].

"A natural extension of our work is to search for similar objects in other systems," says Jahnke.

Future instruments, such as the Atacama Large Millimeter/submillimeter Array, the European Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope will be able to search for such objects at even larger distances from us, probing the connection between black holes and the formation of galaxies in the more distant Universe.

Notes

[1] Supermassive black holes are found in the cores of most large galaxies; unlike the inactive and starving one sitting at the centre of the Milky Way, a fraction of them are said to be active, as they eat up enormous amounts of material. These frantic actions produce a copious release of energy across the whole electromagnetic spectrum; particularly spectacular is the case of quasars, where the active core is so overwhelmingly bright that it outshines the luminosity of the host galaxy.

[2] This part of the study is based on observations performed at mid-infrared wavelengths, with the powerful VLT spectrometer and imager for the mid-infrared (VISIR) instrument at the VLT, combined with additional data including: spectra acquired using VLT-FORS, optical and infrared images from the NASA/ESA Hubble Space Telescope, and radio observations from the Australia Telescope National Facility.

[3] Most galaxies in the local Universe contain a supermassive black hole with a mass about 1/700th the mass of the stellar bulge. The origin of this black hole mass versus stellar mass relation is one of the most debated subjects in modern astrophysics.

Amphibians as Environmental Omen Disputed

2009-11-30T22:38:00.000-08:00

Amphibians, for years considered a leading indicator of environmental degradation, are not uniquely susceptible to pollution, according to a meta-analysis to be published in Ecology Letters.

After a review of over 28,000 toxicological tests, researchers from the University of South Dakota, Yale University and Washington State University are challenging the prevailing view that amphibians, with their permeable skin and aquatic environment, are particularly sensitive to environmental threats and, as such, are "canaries," or predictors of environmental decline.

"The very simple message is that for most of the classes of chemical compounds we looked at, frogs range from being moderately susceptible to being bullet-proof," said David Skelly, professor of ecology at the Yale School of Forestry & Environmental Studies and a member of the research team. "There are lots of other kinds of environmental threats that have led to their decline, including habitat conversion, harvesting for food and the global spread of the Chytrid fungus, which is mowing down these species in its path."

The team, led by Jacob Kerby, an assistant professor at the University of South Dakota, based its analysis on information gleaned from the Environmental Protection Agency's (EPA) Aquatic Toxicity Information Retrieval database, examining 1,279 species, among them segmented worms, fish, bivalves such as clams, insects and snails. Those species were exposed in water to various concentrations of 107 chemical agents, including inorganic chemicals, pesticides, heavy metals and phenols, a class of chemical compound.

"What our results suggest is that all animals are susceptible to chemical stressors and that amphibians are potentially good indicators," said Kerby. "There isn't any evidence that they're a uniquely leading indicator. We tried to be comprehensive in the types of chemicals and organisms that we examined."

In light of the findings, Skelly said, scientists should evaluate the absence, presence or abundance of amphibians in wild populations as "signals" of potential exposure to different chemicals in the environment. "If we have such an understanding for several species, we may be able to use their responses, collectively, as a means of narrowing potential causes of environmental degradation," he said.

The EPA, according to the paper, uses African Clawed Frogs as a proxy for biological diversity when determining a species' sensitivity to chemical exposures, even though that particular species does not occur naturally in North America. "Our knowledge of amphibians' sensitivity to particular chemicals or classes of chemicals has not been used to design assays for effects in nature," Skelly said.

Big Bang machine achieves first particle collisions

2009-11-29T22:22:00.000-08:00

Scientists at the European Organisation for Nuclear Research (CERN) hope experiments will already start giving clues about the origins of the universe in the coming months as the world's biggest particle collider starts moving to full power.

"It's a great achievement to have come this far in so short a time," said CERN Director General Rolf Heuer about the collision, achieved by sending two bunches of subatomic particles around the ring in opposite directions.

It is only three days since the "Big Bang Machine," or Large Hadron Collider (LHC), was switched back on after being halted by an accident 14 months ago, just 10 days after its first start-up.

Earlier, physicist Steve Myers told Reuters it could take until 2011 for beams of protons to hit top velocity in the nearly $10 billion experiment, which involves scientists from dozens of countries.

The key aim of the project at the CERN research center is to try to discover how the universe took shape, after the Big Bang 13.7 billion years ago spilled out matter at vast speeds and energies that eventually became suns, stars, planets and then life itself.

Experiments in a previous collider at the CERN research center near Geneva at the foot of the French Jura mountains staged particle collisions producing energy very close to that of the Big Bang.

The LHC operating at its full might should recreate conditions like those just one billionth of a second after the primeval explosion.

The scientists now plan to increase the beam intensity and accelerate the beams further so they can gather enough collision data by Christmas to help set up experiments.

Species Extinction By Asteroid A Rarity

2009-11-29T22:20:00.000-08:00

In geology as in cancer research, the silver bullet theory always gets the headlines and nearly always turns out to be wrong. For geologists who study mass extinctions, the silver bullet is a giant asteroid plunging to earth

But an asteroid is the prime suspect only in the most recent of five mass extinctions, said USC earth scientist David Bottjer. The cataclysm 65 million years ago wiped out the dinosaurs.

"The other four have not been resolvable to a rock falling out of the sky," Bottjer said.

For example, Bottjer and many others have published studies suggesting that the end-Permian extinction 250 million years ago happened in essence because "the earth got sick."

The latest research from Bottjer's group suggests a similar slow dying during the extinction 200 million years ago at the boundary of the Triassic and Jurassic eras.

At the 2008 Joint Annual Meeting of the Geological Society of America, USC doctoral student Sarah Greene drew similarities between ocean conditions at the Triassic-Jurassic boundary and after the end-Permian extinction.

At both those times, bouquet-like structures of aragonite crystals formed on the ocean floor. Such structures are extremely rare in Earth's history, Greene said.

"The fact that these deposits have only been found at these two specific times that are associated with mass extinction suggests at the very least that maybe there's some shared ocean geochemistry … that could be related to the cause of the extinctions," Greene said.

"The Triassic-Jurassic extinction cause is totally up for grabs at the moment," she added.

Also at the meeting, USC doctoral student Rowan Martindale presented results from her studies of coral reefs during the Triassic-Jurassic extinction.

"The coral reefs look actually very similar to modern coral reefs," she said. "At the end-Triassic mass extinction, you lose all your reef systems. And nobody's figured out why that is."

Martindale identified two distinct types of ancient reefs: one dominated by coral and another consisting mainly of mud and debris, possibly held together by bacteria.

A theory for the end-Triassic extinction needs to explain how both types of reefs could have been killed off, Martindale said.

Any knowledge about end-Triassic reef death could be useful in understanding the current reef crisis, widely attributed to climate change.

"We're looking at it as a model to give us any insight that we might have for today's decline for coral reefs," Bottjer said.

The Joint Annual Meeting was held Oct. 5-9 in Houston. It was the first joint meeting of the Geological Society of America, the Soil Science Society of America, the American Society of Agronomy, the Crop Science Society of America and the Gulf Coast Association of Geological Societies.

Wide Heads Give Hammerhead Sharks Exceptional Stereo View

2009-11-29T22:15:00.000-08:00

Hammerhead sharks are some of the Ocean's most distinctive residents. "Everyone wants to understand why they have this strange head shape," says Michelle McComb from Florida Atlantic University. One possible reason is the shark's vision.

"Perhaps their visual field has been enhanced by their weird head shape," says McComb, giving the sharks excellent stereovision and depth perception.

However, according to McComb, there were two schools of thought on this theory. In 1942, G. Walls speculated that the sharks couldn't possibly have binocular vision because their eyes were stuck out on the sides of their heads. However, in 1984, Leonard Campagno suggested that the sharks would have excellent depth perception because their eyes are so widely separated. "In fact one of the things they say on TV shows is that hammerheads have better vision than other sharks," says McComb, "but no one had ever tested this."

Teaming up with Stephen Kajiura and Timothy Tricas, the trio decided to find out how wide a hammerhead's field of view is and whether they could have binocular vision and publish their results on November 27 2009 in the Journal of Experimental Biology.

Hammerheads come in all shapes and sizes so McComb and Kajiura, opted to work with species with heads ranging from the narrowest to the widest. Fishing for juvenile scalloped hammerheads off Hawaii and bonnethead sharks in the waters around Florida, the team successfully landed the fish and quickly transported them back to local labs to test the fish's eyesight.

The team tested the field of view in each shark's eyes by sweeping a weak light in horizontal and vertical arcs around each eye and recorded the eye's electrical activity. Comparing the hammerheads with pointy nosed species, the team found that the scalloped hammerheads had the largest monocular visual field, at an amazing 182 deg., and the bonnethead had a 176 deg. visual field, which was bigger than that of the pointy nosed blacknose and lemon sharks, at 172 deg. and 159 deg., respectively.

Having collected the animals' monocular visual fields, the team plotted the visual fields of both eyes on a chart of each fish's head to see whether they overlapped. Amazingly, they did. The scalloped hammerhead had a massive binocular overlap of 32 deg. in front of their heads (three times the overlap in the pointy nosed species) while the bonnet head had a respectable 13 deg. overlap. And when the team measured the binocular overlap of the shark with the widest hammerhead, the winghead shark, it was a colossal 48 deg. The hammerheads' wide heads certainly improved their binocular vision and depth perception.

Finally, the team factored in the sharks' eye and head movements and found that the forward binocular overlaps rocketed to an impressive 69 deg. for the scalloped hammerheads and 52 deg. for the bonnetheads. Even more surprisingly, the team realised that the bonnethead and scalloped hammerheads have an excellent stereo rear-view: they have a full 360 deg. view of the world.

"When we first started the project we didn't think that the hammerhead would have binocular vision at all. We thought no way; we were out there to dispel the myth," says McComb. But despite their preconceptions, the team have shown that the sharks not only have outstanding forward stereovision and depth perception, but a respectable stereo rear view too, which is even better than the TV shows would have us believe

Flash Recovery Of Ammonoids After Most Massive Extinction Of All Time

2009-11-29T22:13:00.000-08:00

After the End-Permian extinction 252.6 million years ago, ammonoids diversified and recovered 10 to 30 times faster than previous estimates. The surprising discovery raises questions about paleontologists' understanding of the dynamics of evolution of species and the functioning of the biosphere after a mass extinction.

The study, conducted by a Franco-Swiss collaboration involving the laboratories Biogéosciences (Université de Bourgogne / CNRS), Paléoenvironnements & Paléobiosphère (Université Claude Bernard / CNRS) and the Universities of Zurich and Lausanne (Switzerland), appears in the August 28 issue of Science.

The history of life on Earth has been punctuated by a number of mass extinctions, brief periods of extreme loss of biodiversity. These extinctions are followed by phases during which surviving species recover and diversify. The End-Permian extinction, which took place between the Permian (299 – 252.6 MY) and Triassic (252.6 – 201.6 MY), is the greatest mass extinction on record, resulting in the loss of 90% of existing species. It is associated with intensive volcanic activity in China and Siberia. It marks the boundary between the Paleozoic and Mesozoic Eras. Until now, studies had shown that the biosphere took between 10 and 30 million years to recover the levels of biodiversity seen before the extinction.

Ammonoids are cephalopod swimmers related the nautilus and squid. They had a shell, and disappeared from the oceans at the same time as the dinosaurs, 65 million years ago, after being a major part of marine fauna for 400 MY.

The Franco-Swiss team of paleontologists has shown that ammonoids needed only one million years after the End-Permian extinction to diversify to the same levels as before. The cephalopods, which were abundant during the Permian, narrowly missed being eradicated during the extinction: only two or three species survived and a single species seems to have been the basis for the extraordinary diversification of the group after the extinction. It took researchers seven years to gather new fossils and analyze databases in order to determine the rate of diversification of the ammonoids. In all, 860 genera from 77 regions around the world were recorded at 25 successive time intervals from the Late Carboniferous to the Late Triassic, a period of over 100 million years.

The discovery of this explosive growth over a million years takes a heated debate in a new direction. Indeed, it suggests that earlier estimates for the End-Permian extinction were based on truncated data and imprecise or incorrect dating. Furthermore, the duration for estimated recovery after other lesser extinctions all vary between 5 and 15 million years.

The result obtained here suggests that these estimates should probably be revised downwards. The biosphere is most likely headed towards a sixth mass extinction, and this discovery reminds us that the recovery of existing species after an extinction is a very long process, taking several tens of thousands of human generations at the very least

Mass Extinction: Why Did Half of N. America's Large Mammals Disappear 40,000 to 10,000 Years Ago?

2009-11-29T22:09:00.000-08:00

Years of scientific debate over the extinction of ancient species in North America have yielded many theories. However, new findings from J. Tyler Faith, GW Ph.D. candidate in the hominid paleobiology doctoral program, and Todd Surovell, associate professor of anthropology at the University of Wyoming, reveal that a mass extinction occurred in a geological instant.

During the late Pleistocene, 40,000 to 10,000 years ago, North America lost over 50 percent of its large mammal species. These species include mammoths, mastodons, giant ground sloths, among many others. In total, 35 different genera (groups of species) disappeared, all of different habitat preferences and feeding habits.

What event or factor could cause such a mass extinction? The many hypotheses that have been developed over the years include: abrupt change in climate, the result of comet impact, human overkill and disease. Some researchers believe that it may be a combination of these factors, one of them, or none.

A particular issue that has also contributed to this debate focuses on the chronology of extinctions. The existing fossil record is incomplete, making it more difficult to tell whether or not the extinctions occurred in a gradual process, or took place as a synchronous event. In addition, it was previously unclear whether species are missing from the terminal Pleistocene because they had already gone extinct or because they simply have not been found yet.

However, new findings from Faith indicate that the extinction is best characterized as a sudden event that took place between 13.8 and 11.4 thousand years ago. Faith's findings support the idea that this mass extinction was due to human overkill, comet impact or other rapid events rather than a slow attrition.

"The massive extinction coincides precisely with human arrival on the continent, abrupt climate change, and a possible extraterrestrial impact event" said Faith. "It remains possible that any one of these or all, contributed to the sudden extinctions. We now have a better understanding of when the extinctions took place and the next step is to figure out why."

Earthquakes Actually Aftershocks Of 19th Century Quakes; Repercussions Of 1811 And 1812 New Madrid Quakes Continue To Be Felt

2009-11-08T06:56:00.000-08:00

When small earthquakes shake the central U.S., citizens often fear the rumbles are signs a big earthquake is coming. Fortunately, new research instead shows that most of these earthquakes are aftershocks of big earthquakes (magnitude 7) in the New Madrid seismic zone that struck the Midwest almost 200 years ago.

The study, conducted by researchers from Northwestern University and the University of Missouri-Columbia, will be published in the Nov. 5 issue of the journal Nature.

"This sounds strange at first," said the study's lead author, Seth Stein, the William Deering Professor of Geological Sciences in the Weinberg College of Arts and Sciences at Northwestern. "On the San Andreas fault in California, aftershocks only continue for about 10 years. But in the middle of a continent, they go on much longer."

There is a good reason, explains co-investigator Mian Liu, professor of geological sciences at Missouri. "Aftershocks happen after a big earthquake because the movement on the fault changed the forces in the earth that act on the fault itself and nearby. Aftershocks go on until the fault recovers, which takes much longer in the middle of a continent."

The difference, Stein explains, is that the two sides of the San Andreas fault move past each other at a speed of about one and a half inches in a year -- which is fast on a geologic time scale. This motion "reloads" the fault by swamping the small changes caused by the last big earthquake, so aftershocks are suppressed after about 10 years. The New Madrid faults, however, move more than 100 times more slowly, so it takes hundreds of years to swamp the effects of a big earthquake.

"A number of us had suspected this," Liu said, "because many of the earthquakes we see today in the Midwest have patterns that look like aftershocks. They happen on the faults we think caused the big earthquakes in 1811 and 1812, and they've been getting smaller with time."

To test this idea, Stein and Liu used results from lab experiments on how faults in rocks work to predict that aftershocks would extend much longer on slower moving faults. They then looked at data from faults around the world and found the expected pattern. For example, aftershocks continue today from the magnitude 7.2 Hebgen Lake earthquake that shook Montana, Idaho and Wyoming 50 years ago.

"This makes sense because the Hebgen Lake fault moves faster than the New Madrid faults but slower than the San Andreas," Stein noted. "The observations and theory came together the way we like but don't always get."

Aftershocks go on for long times in other places inside continents, Stein said. It even looks like we see small earthquakes today in the area along Canada's Saint Lawrence valley where a large earthquake occurred in 1663.

The new results will help investigators in both understanding earthquakes in continents and trying to assess earthquake hazards there. "Until now," Liu observed, "we've mostly tried to tell where large earthquakes will happen by looking at where small ones do." That's why many scientists were surprised by the disastrous May 2008 magnitude 7.9 earthquake in Sichuan, China -- a place where there hadn't been many earthquakes in the past few hundred years.

"Predicting big quakes based on small quakes is like the 'Whack-a-mole' game -- you wait for the mole to come up where it went down," Stein said. "But we now know the big earthquakes can pop up somewhere else. Instead of just focusing on where small earthquakes happen, we need to use methods like GPS satellites and computer modeling to look for places where the earth is storing up energy for a large future earthquake. We don't see that in the Midwest today, but we want to keep looking."

Seafloor Fossils Provide Clues To Climate Change

2009-11-08T06:55:00.000-08:00

Deep under the sea, a fossil the size of a sand grain is nestled among a billion of its closest dead relatives. Known as foraminifera, these complex little shells of calcium carbonate can tell you the sea level, temperature, and ocean conditions of Earth millions of years ago. That is, if you know what to look for.

Assistant Professor of Earth and Environmental Sciences at Rensselaer Polytechnic Institute Miriam Katz has spent the past two decades studying these ancient, deep-sea fossils to reconstruct the climates of Earth up to 250 million years ago. Through ice ages and greenhouse climates, Katz has been able to piece together oxygen, carbon, and faunal data to paint a portrait of how, when, and why our climate has changed so drastically over geologic history. In addition, her investigations into the deep past of Earth have important implications for understanding and tracking the potential drastic repercussions of modern, human-induced climate change.

"There is a saying among scientists in my field that 'the past is a window on the future,' " Katz said. "By reconstructing the climates of the past, particularly those where we see massive and rapid changes in the climate, we can provide a science-based means to explore or predict possible system responses to the current climate change."

While her work requires a lot of time in the laboratory, Katz has spent nearly two years at sea on seven different ocean voyages around the world to drill for foraminifera as part of the Integrated Ocean Drilling Program (IODP), an international marine research effort that explores the Earth's history and structure by looking at seafloor sediments and rocks. During each two-month IODP excursion, Katz and the other scientists on board never set foot on land and spend hours poking through the millions of layers of sediment, trapped gases, fossils, and trace elements found in huge cores drilled from deep under the seafloor.

Just a few inches in diameter, each core is painstakingly drilled and removed from the seafloor. From top to bottom, the core provides a reverse chronology of the various organisms, sediments, and elements that were found on Earth throughout history. Unlike cores from sedimentary layers from the continents that are quickly destroyed by the forces of plate tectonics, wind, and water, these rarely disturbed ocean sediment cores can provide records up to 180 million years ago as new layers of sediment bury and preserve those of the past.

Katz is most interested in the foraminifera found in the cores. The foraminifera she studies live on or just below the seafloor. When they die, their hard shells are incorporated in the surrounding sediments and buried over time in a nearly uniform layer.

The assemblages of foraminifera in each layer can provide valuable information on the climate of that time. "Some species are only found in certain environments, such as in warm water or in shallow, tidal areas," Katz said. "By piecing together the species assemblages that are found in a given area during the given time period, we can reconstruct the sea level and ocean and climate conditions of that period based on our knowledge of each foraminiferal species."

In addition to the specific type of foraminifera seen in each layer, valuable information can also be gathered by looking at variations in the chemical structure of the fossilized calcium carbonate (CaCO3) shell seen in the various layers. During their life, the foraminiferal shells are formed from the elements found in the seas that they lived in. The ratios of various isotopes of the elements carbon and oxygen found in foraminiferal shells at different times in Earth's history provide important information needed to reconstruct the climate and ocean waters that surrounded them during their short lives millions of years ago.

In the case of oxygen (O), the ratio between isotopes 18O and 16O tells scientists how much water is trapped in glacial ice, providing important clues about temperature and the size of the ancient continental ice sheets. Carbon (C) in the shells can be analyzed for either 12C or 13C isotopes. Plants prefer to incorporate lighter 12C during photosynthesis, increasing the ratio of 13C to 12C in foraminifera when plant and algae production is high. This carbon data provides clues on the types and amounts of vegetation at various times as well as ocean circulation, according to Katz.

Gathering this information from cores has allowed Katz to develop important theories on one of the most recent and dramatic climate change events that has occurred in recent geologic history -- the transition from the greenhouse climate of the Eocene epoch to the "icehouse" or glacial conditions of the Oligocene epoch approximately 33.5 million years ago.

"The boundary between the late Eocene to the early Oligocene is a striking example of rapid climate change that we can look to in Earth's past," Katz said. "Information from this period can provide us with important information on how rapid changes in temperature can significantly impact ice volume, sea level, and the evolution of life on Earth."

Katz has used oxygen and carbon isotopes as well as the ratio of magnesium to calcium within foraminifera from this period to reconstruct the changes that occurred as the climate rapidly cooled. Along with her research colleagues, she has shown that ice sheets at the end of the transition were approximately 25 percent larger than today, causing a decrease in sea level of approximately 105 meters.

Her research also reaches even further back to reconstruct conditions earlier in Earth's history. In particular, she took part in a study of atmospheric oxygen and carbon dioxide concentrations since the Jurassic period 205 million years ago. The group has found that oxygen levels doubled in the short period of time from the Jurassic period to the Eocene epoch (~150 million years ago), providing a climate with just enough oxygen for placental mammals to develop.

'Duck-billed' Dinosaurs: Last European Hadrosaurs Lived In Iberian Peninsula

2009-11-08T06:51:00.000-08:00

Spanish researchers have studied the fossil record of hadrosaurs, the so-called 'duck-billed' dinosaurs, in the Iberian Peninsula for the purpose of determining that they were the last of their kind to inhabit the European continent before disappearing during the K/T extinction event that occurred 65.5 million years ago. Most notable among these fossils is the discovery of a new hadrosaur, the Arenysaurus ardevoli, found in Huesca, Spain.

A few million years before the catastrophic event that led to the extinction of dinosaurs (with the exception of birds), several species of hadrosaurs coexisted in the Iberian Peninsula. This is what a Spanish team of paleontologists have demonstrated in a research article published in the Journal of Vertebrate Paleontology.

"The Iberian archeological record is important from an European context due to the quantity and quality of the fossil material discovered," explains Xavier Pereda-Suberbiola, one of the study's authors and a researcher at the University of the Basque Country (UPV / EHU).

The researcher, collaborating with paleontologists from the University of Zaragoza, Valencia, Complutense of Madrid, Autonoma de Barcelona and the Jurassic Museum of Asturias, specifies that the presence of evolved hadrosaurs in Europe could be due to migration from Asia and North America.

"In Europe, primitive hadrosaurs coexist with evolved hadrosaurs, and the persistence of basal members could be due to the insular palaeobiogeography of Europe during the Upper Cretaceous," states the scientist. In addition to the fossils found in the Iberian Peninsula, hadrosaur fossils have been found in the Netherlands, which date back to Late Cretaceous, "although the material is more fragmented than those found in Huesca and Lleida," adds Pereda-Suberbiola.

During that time period, Europe was isolated from other continents and this may have led to the survival of certain lineages. "The European hadrosaur faunas are different from those seen in North America and Asia, which are both dominated by evolved species," explains Pereda-Suberbiola.

Next to the hadrosaurs, identifiable by the fossilized mandibles found in the arechological sites of La Solana (Valencia) and Fontllonga (Lleida), were a lambeosaurine hadrosaurs yet to be defined, and a newly discovered lambeosaurine, the Arenysaurus ardevoli.

An articulated cranium of great value

The study of the last hadrosaurs that lived in the Iberian Peninsula has been possible thanks to the discovery by the Aragosaurus-IUCA Group of the University of Zaragoza, led by Jose Ignacio Canudo, of the first articulated hadrosaur skull found in southern Europe, from the archeological sites of Arén, in Huesca, Spain.

The skull belongs to an Arenysaurus ardevoli, a lambeosaurine (hadrosaur with a hollow cranial crest), whose description was recently published in the French journal Comptes Rendus Palevol, and was part of the Spanish fossil record.

According to paleontologists, the new lambeosaurine lived between 65.5 and 68 million years ago, had a very prominent frontal dome, and its biogeographical relationships suggest a paleobiogeographical connection between Asia and Europe during the Late Cretaceous.

Researchers have found, in addition to the partially articulated skull, the mandibular remains and postcranial elements such as vertebrae, girdle and limb bones.

The Spanish archaeological record of hadrosaurs is the largest in Europe. Out of the 50 locations where dinosaur remains were discovered since 1984, nearly half have been found in Lleida and Huesca. These archeological sites stand out for containing fossils pertaining to several species of duck-billed dinosaurs.

Scientists Make Explosive Discovery About Nature Of Supernovae

2009-11-07T05:41:00.000-08:00

North Carolina State University astrophysicists have answered a long-standing question about the nature of one of our galaxy’s most famous supernova explosions, discovering a new class of supernova in the process.

Dr. Stephen Reynolds, astrophysicist in NC State’s College of Physical and Mathematical Sciences, along with colleague Dr. Kazik Borkowski and a team of scientists from NASA, Rutgers University, and the Naval Research Laboratories, set out to determine whether the Kepler supernova, which occurred in 1604 A.D., was a core collapse supernova or a thermonuclear supernova.

They revealed their results in a press conference today at the annual meeting of the American Astronomical Society.

A core collapse supernova occurs when a single, massive star (with a mass eight times greater – or more – than that of our sun) reaches the end of its life and explodes. Core collapse supernovae leave pulsars, rapidly spinning neutron stars, behind when they occur. They also tend to be surrounded by circumstellar medium – leftover elements from the star that collapsed, as well as large amounts of oxygen and small amounts of iron. These supernovae are usually located near “star-forming” sites along a galaxy’s edge.

Thermonuclear, or Type Ia, supernovae occur when a white dwarf star, which typically travels through space with a companion star that eventually “leaks” its own mass onto the dwarf, reaches its mass limit and explodes. These supernovae can be found all over a galaxy, are typically not associated with any circumstellar medium, and produce large amounts of iron.

The Kepler supernova has long puzzled scientists because it has features that are common to both types of supernova: The Kepler supernova’s location and the presence of a lot of iron are indicative of a Type Ia supernova, but the dense surroundings and nitrogen-enriched circumstellar medium are commonly associated with the aftermath of a core collapse.

Reynolds and his team used the powerful Chandra X-ray telescope to observe the Kepler supernova, and they discovered that Kepler is something entirely new: a Type Ia supernova in which the progenitor of the white dwarf star that created it had enough mass to create circumstellar medium.

“We really don’t know much about Type Ia supernovae, and they’re really important to our understanding of the universe,” Reynolds says. “We use the fact that they all have similar luminosities, or brightness, to calculate the distance of galaxies and to determine how much and how quickly the universe is expanding.

“Type Ia’s are also the source of the majority of iron in the universe, and can give us a lot of information about its chemical history. A new class of Type Ia supernova will have huge implications for our ability to understand the source of the elements that create our universe.”

NASA'S Swift Sees Double Supernova In Galaxy

2009-11-07T05:40:00.000-08:00

In just the past six weeks, two supernovae have flared up in an obscure galaxy in the constellation Hercules. Never before have astronomers observed two of these powerful stellar explosions occurring in the same galaxy so close together in time.

The galaxy, known as MCG +05-43-16, is 380 million light-years from Earth. Until this year, astronomers had never sighted a supernova popping off in this stellar congregation. A supernova is an extremely energetic and life-ending explosion of a star.

Making the event even more unusual is the fact that the two supernovae belong to different types. Supernova 2007ck is a Type II event – which is triggered when the core of a massive star runs out of nuclear fuel and collapses gravitationally, producing a shock wave that blows the star to smithereens. Supernova 2007ck was first observed on May 19.

In contrast, Supernova 2007co is a Type Ia event, which occurs when a white dwarf star accretes so much material from a binary companion star that it blows up like a giant thermonuclear bomb. It was discovered on June 4, 2007. A white dwarf is the exposed core of a star after it has ejected its atmosphere; it’s approximately the size of Earth but with the mass of our Sun.

"Most galaxies have a supernova every 25 to 100 years, so it’s remarkable to have a galaxy with two supernovae discovered just 16 days apart," says Stefan Immler of NASA’s Goddard Space Flight Center. In 2006 Immler used NASA’s Swift satellite to image two supernovae in the elliptical galaxy NGC 1316, but both of those explosions were Type Ia events, and they were discovered six months apart.

The simultaneous appearance of two supernovae in one galaxy is an extremely rare occurrence, but it’s merely a coincidence and does not imply anything unusual about MCG +05-43-16. Because the two supernovae are tens of thousands of light-years from each other, and because light travels at a finite speed, astronomers in the galaxy itself, or in a different galaxy, might record the two supernovae exploding thousands of years apart.

Rapid Supernova Could Be New Class Of Exploding Star

2009-11-07T05:38:00.000-08:00

An unusual supernova rediscovered in seven-year-old data may be the first example of a new type of exploding star, possibly from a binary star system where helium flows from one white dwarf onto another and detonates in a thermonuclear explosion.

In a paper first published online Nov. 5 in the journal Science Express, University of California, Berkeley, and Lawrence Berkeley National Laboratory (LBNL) astronomer Dovi Poznanski and his colleagues describe the outburst, dubbed SN 2002bj, and why they believe it is a new type of explosion.

"This is the fastest evolving supernova we have ever seen," said Poznanski, a UC Berkeley post-doctoral fellow who recently joined LBNL's Computational Cosmology Center. "It was three to four times faster than a standard supernova, basically disappearing within 20 days. Its brightness just dropped like a rock."

This rapid drop, coupled with the supernova's faintness, the strong signature of helium in the spectrum of the explosion, the absence of hydrogen, and the possible presence of vanadium -- an element never previously identified in supernova spectra -- points toward helium detonation on a white dwarf, the astronomers said.

"We think this may well be a new physical explosion mechanism, not just a minor variation of ones already known," said co-author Alex Filippenko, UC Berkeley professor of astronomy. "This supernova is qualitatively different from the complete disruption of a white dwarf, known as a Type Ia supernova, or the collapse of an iron core and rebound of the surrounding material, so-called 'core-collapse supernovae.'"

Co-author Joshua Bloom, UC Berkeley associate professor of astronomy, also views SN 2002bj as a "new beast" quite different from the two well-known classes of supernovae.

"We have seen great diversity in those two main supernova mechanisms, but even within that diversity, observationally, there is a limited range of variation spectrally and in how events evolve in time," he said. "This object (SN 2002bj) falls outside that range."

The supernova was detected in 2002 in the galaxy NGC 1821, in the constellation Lepus, by Filippenko's Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory near San Jose as well as by amateur astronomers. Due to an unfortunate alignment of circumstances, the supernova was erroneously classified by the astronomical community as a common Type II supernova and filed away.

In June, Poznanski happened upon the spectrum while searching for Type II supernovae he hopes to use as distance indicators to confirm the accelerating expansion of the universe. When he carefully examined a high-quality spectrum of SN 2002bj, he realized that the supernova was not a Type II at all, but an unusual kind of supernova more akin to a Type Ia.

The spectrum had been obtained seven days after its discovery by Filippenko and Douglas Leonard, at the time a UC Berkeley graduate student, now an assistant professor of astronomy at San Diego State University, using the Keck I telescope.

"Its classification was a mistake, which is understandable given the conditions of the data. But, of course, a redress of old data with fresh eyes is not usually this fruitful," Leonard said.

Pulling out follow-up images made by KAIT, Poznanski and UC Berkeley graduate student Mohan Ganeshalingam found that the brightness of SN 2002bj dropped off so rapidly that the supernova disappeared 20 days after its discovery. An image of that area of the sky taken seven days prior to its discovery showed no supernova, so it had brightened and dimmed into obscurity in less than 27 days, whereas most supernovae brighten and dim over three to four months.

Searching through thousands of supernovae spectra, Poznanski and graduate student Ryan Chornock -- now a post-doctoral fellow at Harvard University -- could find none that had such an awkward composition, but they did come across a theory of fast but faint supernovae that seemed to fit.

Proposed by Lars Bildsten and colleagues -- Bildsten is a professor of physics at the Kavli Institute for Theoretical Physics at UC Santa Barbara -- the theory involves AM Canum Venaticorum (AM CVn) binary systems, which are composed of two white dwarfs, one of which is primarily made of helium that is being slowly pulled by gravity onto its companion. White dwarfs are the remnants of stars that burned their hydrogen down to carbon and oxygen or, in some particular cases, to helium.

In a 2007 Astrophysical Journal Letters paper, Bildsten and colleagues proposed that in AM CVn systems, when enough helium has been accumulated on the surface of the primary white dwarf, an explosion will occur that can "power a faint … and rapidly rising (few days) thermonuclear supernova."

Christopher Stubbs, chair of the Department of Physics at Harvard University, jokingly dubbed it a ''.Ia'' (point one A) supernova, because it is one-tenth as bright for one-tenth the time as a Type Ia supernova, and the name stuck.

Filippenko noted that this explosion is nothing like a regular Type Ia explosion because the white dwarf survives the detonation of the helium shell. In fact, it has similarities to both a nova and a supernova. Novas occur when matter -- primarily hydrogen -- falls onto a star and accumulates in a shell that can flare up as brief thermonuclear explosions. SN 2002bj is a "super" nova, generating about 1,000 times the energy of a standard nova, he said.

The explosion would have created heavy elements such as chromium, which decays to vanadium and thence to titanium. Thus, absorption lines of vanadium could be expected, Poznanski said.

Filippenko noted that the past few years have "yielded a bonanza of weird supernovae."

"A lot of us who have studied supernovae for several decades are amazed at the quality and quantity of data coming in recently, showing interesting new subclasses or even strange new physical classes of supernovae," he said. "It whets my appetite for what else we might find out there with these large, wide-sky surveys like the Palomar Transient Factory, Dark Energy Survey and the Large Synoptic Survey Telescope. KAIT has discovered about 800 supernovae, but these new surveys will find thousands or hundreds of thousands of supernovae."

Poznanski, too, is expecting the current Palomar Transient Factory, which uses a wide-field camera to search the sky daily for new objects, to find more supernovae like SN 2002bj. The factory is a project led by Shri Kulkarni, professor of astronomy at the California Institute of Technology (Caltech), and involves many of the co-authors on the Science Express paper, including Peter Nugent, co-leader of the Computational Cosmology Center at LBNL, who runs the search for transients.

"The Palomar survey will be able to find many rare objects, like SN 2002bj, by scanning huge parts of the sky and not limit itself to the big, bright and nearby galaxies," Poznanski said.

Coauthors with Poznanski, Filippenko, Nugent, Ganeshalingam, Leonard, Chornock and Bloom are Rollin C. Thomas, a member of the Computational Cosmology Center, and Weidong Li of UC Berkeley's Department of Astronomy.

The research was funded by the National Science Foundation, the Department of Energy, the Sylvia and Jim Katzman Foundation and the TABASGO Foundation, with observational assistance from the University of California Lick Observatory and the W. M. Keck Observatory in Hawaii.

Carbon Atmosphere Discovered On Neutron Star

2009-11-06T06:01:00.000-08:00

Evidence for a thin veil of carbon has been found on the neutron star in the Cassiopeia A supernova remnant. This discovery, made with NASA's Chandra X-ray Observatory, resolves a ten-year mystery surrounding this object.

"The compact star at the center of this famous supernova remnant has been an enigma since its discovery," said Wynn Ho of the University of Southampton and lead author of a paper that appears in the November 5 issue of Nature. "Now we finally understand that it can be produced by a hot neutron star with a carbon atmosphere."

By analyzing Chandra's X-ray spectrum -- akin to a fingerprint of energy -- and applying it to theoretical models, Ho and his colleague Craig Heinke, from the University of Alberta, determined that the neutron star in Cassiopeia A, or Cas A for short, has an ultra-thin coating of carbon. This is the first time the composition of an atmosphere of an isolated neutron star has been confirmed.

The Chandra "First Light" image of Cas A in 1999 revealed a previously undetected point-like source of X-rays at the center. This object was presumed to be a neutron star, the typical remnant of an exploded star, but researchers were unable to understand its properties. Defying astronomers' expectations, this object did not show any X-ray or radio pulsations or any signs of radio pulsar activity.

By applying a model of a neutron star with a carbon atmosphere to this object, Ho and Heinke found that the region emitting X-rays would uniformly cover a typical neutron star. This would explain the lack of X-ray pulsations because -- like a lightbulb that shines consistently in all directions -- this neutron star would be unlikely to display any changes in its intensity as it rotates.

Scientists previously have used a neutron star model with a hydrogen atmosphere giving a much smaller emission area, corresponding to a hot spot on a typical neutron star, which should produce X-ray pulsations as it rotates. Interpreting the hydrogen atmosphere model without pulsations would require a tiny size, consistent only with exotic stars made of strange quark matter.

"Our carbon veil solves one of the big questions about the neutron star in Cas A," said Craig Heinke. "People have been willing to consider some weird explanations, so it's a relief to discover a less peculiar solution."

Unlike most astronomical objects, neutron stars are small enough to understand on a human scale. For example, neutron stars typically have a diameter of about 14 miles, only slightly longer than a half-marathon. The atmosphere of a neutron star is on an even smaller scale. The researchers calculate that the carbon atmosphere is only about 4 inches thick, because it has been compressed by a surface gravity that is 100 billion times stronger than on Earth.

"For people who are used to hearing about immense sizes of things in space, it might be a surprise that we can study something so small," said Ho. "It's also funny to think that such a thin veil over this star played a key role in frustrating researchers."

In Earth's time frame, the estimated age of the neutron star in Cas A is only several hundred years, making it about ten times younger than other neutron stars with detected surface emission. Therefore, the Cas A neutron star gives a unique window into the early life of a cooling neutron star.

The carbon itself comes from a combination of material that has fallen back after the supernova, and nuclear reactions on the hot surface of the neutron star which convert hydrogen and helium into carbon.

The X-ray spectrum and lack of pulsar activity suggest that the magnetic field on the surface of this neutron star is relatively weak. Similarly low magnetic fields are implied for several other young neutron stars by study of their weak X-ray pulsations. It is not known whether these neutron stars will have low magnetic fields for their entire lives, and never become radio pulsars, or whether processes in their interior will lead to the development of stronger magnetic fields as they age.

Are The Alps Growing Or Shrinking?

2009-11-06T05:59:00.000-08:00

The Alps are growing just as quickly in height as they are shrinking. This paradoxical result comes from a new study by a group of German and Swiss geoscientists.

Due to glaciers and rivers, about exactly the same amount of material is eroded from the slopes of the Alps as is regenerated from the deep Earth's crust. The climatic cycles of the glacial period in Europe over the past 2.5 million years have accelerated this erosion process. In the latest volume of the science magazine Tectonophysics ( No. 474, S.236-249) the scientists show that today's uplifting of the Alps is driven by these strong climatic variations

The formation of the Alps through the collision of the two continents Africa and Europe began about approximately 55 million years ago. This led to the upthrusting of the highest European mountains, which probably already achieved its greatest height some millions of years ago. At present, however, the Swiss Alps are no longer growing as a result of this tectonic process.

Swiss geodesists, who have already been measuring the Alps with highest accuracy for decades, have observed, however, that the Alp summits, as compared to low land, rise up to one millimetre per year. Over millions of years a considerable height would have to result. But why then are the Alps not as high as the Himalayas? Researchers from the GFZ German Research Centre for Geosciences were able to calculate that mountains eroded concurrently at almost exactly the same speed.

"This mountain erosion cannot even be determined using the highly precise methods of modern geodesy," explains Professor Friedhelm v. Blanckenburg from the GFZ. "We use the rare isotope Beryllium-10, which develops in the land surface via cosmic radiation. The quicker a surface erodes, the fewer isotopes of this type are present therein." Therefore, von Blanckenburg, and the GFZ geoscientist, Dr. Hella Wittmann, have analysed this "cosmogenic" isotope in the sand of the Swiss Alps rivers and, thus, in the direct products of erosion.

How does it come about now that the Alps erode at the same speed that they rise? "Here pure upthrusting forces are at work. It is similar to an iceberg in the sea. If the top melts, the iceberg surfaces out of the water by almost the same share," explains von Blanckenburg. Thus this paradoxical situation with the Alps that through wind, water, glaciers and rock fall, they are being constantly finely eroded from the top but on the other hand, regenerated from the Earth's mantle. This phenomenon, even if already postulated theoretically has now been proven for a complete mountain range for the first time.

Thus, the Alps are constantly rising, although they have been deemed "dead" in a tectonic sense. Instead of plate forces it is the strong climatic variations since the beginning of the so-called quaternary glacial before approximately 2.5 million years, to which mountain slopes in particular have been reacting so sensitively. This holds the Alps in motion.

Caught In The Act: Butterfly Mate Preference Shows How One Species Can Become Two

2009-11-06T05:57:00.000-08:00

Breaking up may actually not be hard to do, say scientists who've found a population of tropical butterflies that may be on its way to a split into two distinct species.

The cause of this particular break-up? A shift in wing color and mate preference.

In a paper published this week in the journal Science, the researchers describe the relationship between diverging color patterns in Heliconiusbutterflies and the long-term divergence of populations into new and distinct species.

"Our paper provides a unique glimpse into the earliest stage of ecological speciation, where natural selection to fit the environment causes the same trait in the same population to be pushed in two different directions," says Marcus Kronforst, a Bauer Fellow in the Center for Systems Biology at Harvard University who received his doctor's degree at The University of Texas at Austin. "If this trait is also involved in reproduction, this process can have a side effect of causing the divergent subpopulations to no longer interbreed. This appears to be the process that is just beginning among Heliconius butterflies in Ecuador."

Heliconius butterflies display incredible color pattern variation across Central and South America, with closely related species usually sporting different colors. In Costa Rica, for example, the two most closely related species differ in color: One species is white and the other is yellow. In addition, both species display a marked preference to mate with butter-flies of the same color.

The Ecuadorian population examined by Kronforst and his colleagues shows the same white and yellow variation found in Costa Rica but has not yet reached a level of strong reproductive isolation. The entire population lives in close proximity and individuals of both colors come in contact with -- and mate with -- each other.

But, by studying the Ecuadorian population in captivity, the scientists found the two colors do not mate randomly. Despite the genetic similarity between the groups -- white and yellow varieties differ only at the color-determining gene -- yellow Ecuadorian individuals show a preference for those of the same color. White male butterflies, most of which are heterozygous at the gene that controls color, show no color preference.

"This subtle difference in mate preference between the color forms in Ecuador may be the first step in a process that could eventually result in two species, as we see in Costa Rica," says Kronforst, who began studies of Heliconius color pattern and behavioral genetics in the laboratory of Professor Lawrence Gilbert at The University of Texas at Austin.

Previous studies of species formation have focused on the characteristics of well-differentiated species, and the health and viability of their hybrids in particular, in an effort to identify how the species may have emerged and how they stay distinct.

Heliconius provides a model for a different kind of study. The researchers considered species emergence from the opposite end, studying populations that have yet to diverge into separate species in order to identify the role of mate choice in the potential emergence of new species.

Having identified color-based mate preference in Heliconius, the researchers used a battery of genetic markers to compare the genomes of the white and yellow varieties, showing that they are genetically identical except for their different colors and preferences.

Their work suggests that the genes for color and preference are very close to one another in the genome; the two traits could even be caused by the same gene. Their next step is to identify the gene (or genes) responsible for the differences in color and mate preference.

"If we can identify this gene or genes, we can say conclusively how they influence both color and mate choice," says Kronforst. "Subsequent work could elucidate exactly how changes in individual genes can, over long periods of time, lead to novel species."

"This study shows the great potential of the genus Heliconiusas a model system for integrating genetics, development, behavior, ecology and evolution," says Gilbert, professor in the Section of Integrative Biology. "It is the culmination of diverse contributions of the co-authors involving insectary, field and laboratory research over more than a decade."

Co-authors on the Science paper with Kronforst are Nicola L. Chamberlain and Ryan I. Hill, both of Harvard; Durrell D. Kapan of the University of Hawaii; and Lawrence E. Gilbert of The University of Texas at Austin. Their work was funded by the National Science Foundation and the National Institutes of Health.

Timber Harvest Impacts Amphibians Differently During Life Stages

2009-11-05T05:50:00.000-08:00

Frogs are croaking in clear-cut forests, but not exactly in their traditional manner. University of Missouri researchers found that removing all of the trees from a section of the forest had a negative effect on amphibians during their later life cycles, but had some positive effects during amphibians' aquatic larva stages at the beginning of their lives. To lessen the negative effects during the later life stage, scientists recommend partial or selection cuts to forests rather than completely removing trees from an area. Removing only a portion of trees and canopy allows amphibians to persist better.

The ultimate goal is not to stop the harvest of trees, but to find techniques that can sustain economically valuable timber harvests and protect forest ecosystems, including many species of amphibians, said Ray Semlitsch, Curators' Professor of Biological Science in the College of Arts and Science. Amphibians may be critical for the transfer of nutrients, such as nitrogen from ponds and streams into the uplands for consumption by plants and other forest creatures.

"Amphibians are good bio-indicators of the health of an environment," Semlitsch said. "When amphibians aren't doing well, it's a warning that the rest of the ecosystem isn't doing well. They are sensitive to temperature and water loss and take on the same temperature as the area around them. Because of their sensitivity, amphibians are the most endangered of the vertebrates. About one-third of the species world-wide are in danger of extinction."

In the study, researchers examined how clear-cutting and timber harvest techniques affect amphibians during different life stages. Surprisingly, researchers found that timber harvest has a positive effect on the aquatic stage of the amphibian's life. Without shade over the pond, algae grew faster in direct sunlight and productivity in the pond increased. The larval amphibians ate the increased algae and grew larger and faster. However, this benefit was temporary; when amphibians left the pond, they were more likely to die.

"The trouble starts for amphibians the moment they walk out of the pond," Semlitsch said. "When you remove all the trees from the forest, it has devastating effects on the amphibian population. Without a canopy above, open areas basically cook amphibians."

The study was a coordinated effort during a five-year period in three different locations in Maine, South Carolina and Missouri. Researchers were able to cross reference what was happening to the same types of frogs and salamanders in the three locations. Prior studies have been conducted on amphibians in clear-cut environments, but this was the first to compare data during different stages of life across multiple regions.

The study, "Effects of Timber Harvest on Amphibian Populations: Understanding Mechanisms from Forest Experiments," recently was published in BioScience.

Why Do Animals, Especially Males, Have So Many Different Colors?

2009-11-05T05:49:00.000-08:00

Why do so many animal species -- including fish, birds and insects -- display such rich diversity in coloration and other traits? In new research, Gregory Grether, UCLA professor of ecology and evolutionary biology, and Christopher Anderson, who recently earned his doctorate in Grether's laboratory, offer an answer

At least since Charles Darwin, biologists have noticed that species differ in "secondary sexual traits," such as bright coloring or elaborate horns, Grether said. Darwin attributed this diversity to sexual selection, meaning the traits increased an animal's ability to attract mates.

But Grether and Anderson, writing in the Oct. 28 issue of the journalProceedings of the Royal Society B: Biological Sciences, emphasize another evolutionary factor.

"The cost of attacking the wrong type of male and of being attacked by the wrong type of male favors the rich diversity of coloration and of birdsong and chemical cues, such as odors, to identify rivals," Grether said.

Grether and Anderson studied several species of the Hetaerinadamselfly (closely related to dragonflies) and found that differences in coloration served to help damselflies distinguish males of their own species, who are rivals, from those of other species, who are not.

"We found that male Hetaerina damselflies use species differences in wing coloration to distinguish between intruders of their own species and intruders of other damselfly species, but only at sites where the two species naturally occur together," he said. "This provides one of the clearest demonstrations yet of an evolutionary process that is probably very prevalent in nature but which has largely been overlooked. We tested for shifts in what animals recognize as competitors."

Nobel Prize-winning Austrian ethologist and zoologist Konrad Lorenz suggested in 1962 that the spectacularly diverse coloration of coral reef fish was likely due to selection against fighting with the wrong species.

"Just as there could be selection against mating with the wrong species, there can also be selection against fighting with the wrong species," Grether said. "Lorenz said there was no advantage to coral reef fish attacking species that are close in proximity but are not competitors. The idea never really reached the level of attention in evolutionary biology that it deserved."

Lorenz's idea may not accurately explain the color diversity of coral reef fish, Grether said, but it may explain the diversity of coloration of other animal groups.

"When species are found in the same location, they do a better job of telling apart males of their own species from males of the other species than they do in places where they do not occur together," Grether said.

At sites where only one damselfly species occurs naturally, the researchers tested their theory by using members of that species whose wings had been artificially colored to resemble males of another damselfly species.

"We can test their responses at both kinds of sites, and we found they show greater discrimination between males of their own species and of other species at places where they actually have to contend with the other species than at places where they don't. They differentiate based on color," Grether said. "That this ability has evolved as a result of selection against fighting with other species is suggested quite strongly by the fact that in places where the other species do not occur, they do not make that distinction.

"If there is no reason for two species to interact aggressively with each other -- as Lorenz argued with coral reef fish -- then you would expect evolution to favor the ability for them to tell the difference by, for example, an exaggeration in the initial difference in color between them," Grether said. "Differences in color might enable females to more readily tell their own males apart from males of other species. Selection against interspecies aggression could favor the evolution of increased differences between species in color."

Some damselflies species also differ more in coloration where they occur together than where they occur alone, but "this finding can be explained either by selection against mating with the wrong species or selection against fighting with the wrong species," Grether said.

In future research, Grether hopes to learn what proportion of species can tell the difference between members of their own species and members of other species and whether they respond more strongly to their own species in a competitive context. Interspecies aggression and the evolutionary effect it has are understudied scientific questions, Grether said.

In addition to studying several species of damselflies in Mexico and Texas, Grether and Anderson collaborated with modeler Kenichi Okamoto to construct a mathematical model of what happens when species with similar secondary sexual traits come into contact. The model, published in the November 2009 issue of the journal Biological Reviews, predicts rapid evolutionary shifts in secondary sexual traits and also in what the animals recognize as competitors.

"My reading of the evidence," Grether said, "is that these evolutionary processes are important."

The research is federally funded by the National Science Foundation, and by UC MEXUS.

Oceanography: Low Summer Iron Availability Limits Biological Production In The High-latitude North Atlantic

2009-11-05T05:29:00.000-08:00

Southampton scientists have demonstrated an unexpected role of iron in regulating biological production in the high-latitude North Atlantic. Their findings have important implications for our understanding of ocean-climate interactions.

Tiny plant-like organisms called phytoplankton dominate biological production in the sunlit surface waters of the world's oceans and, through the process of photosynthesis, sequester large amounts of atmospheric carbon dioxide. A proportion of the carbon is exported to the deep ocean, and because carbon dioxide is a greenhouse gas, this so-called 'biological carbon pump' helps prevent runaway global climate warming.

Iron is an essential micro nutrient for phytoplankton growth. In high-nutrient, low-chlorophyll (HNLC) oceanic regions, phytoplankton growth is limited by low iron availability. Classical HNLC regions, which account for about a third of the world's oceans, include the Southern Ocean and the subpolar North Pacific.

In contrast, it has been widely assumed that iron supply does not limit biological production of the high-latitude (>50 degrees N) North Atlantic Ocean. Here, winter cooling causes the sinking of nutrient-depleted surface waters and their replacement by deep nutrient-rich water. This winter 'overturning' replenishes surface water nutrients, and in the spring, when light intensities increase, a large phytoplankton bloom develops, leading to high rates of carbon export.

However, in many regions of the open North Atlantic, including the Iceland and Irminger Basins, residual amounts of nitrate persist into the summer period, after the spring bloom has ceased. This represents an inefficiency of the biological carbon pump that is potentially of global significance to the partitioning of carbon between the atmosphere and ocean.

Phytoplankton are grazed upon and some of the larger phytoplankton species such as diatoms with low grazing mortality are susceptible to silicate shortage. Traditionally, it has been believed that these factors, acting in concert, might be sufficient to terminate the spring bloom leaving some nitrate unused. However, there have been indications that phytoplankton might simply run out of iron before they are able to exploit any remaining other nutrients.

Now a team of scientists from the National Oceanography Centre, Southampton, have tested this 'iron limitation hypothesis' for the high-latitude North Atlantic Ocean. Their measurements were performed on a cruise aboard the RRS Discovery within the central Iceland Basin during the summer of 2007, and the findings are published this month in the scientific journal Global Biogeochemical Cycles.

The researchers found that the concentration of dissolved iron in surface waters was very low, as was biological production, despite the presence of residual nitrate. Experimental addition of iron to bottles containing seawater samples increased photosynthetic efficiency, chlorophyll concentrations, and growth of several types of phytoplankton, including the ubiquitous Emiliania huxleyi, a coccolithophore.

"These results, backed up by additional experiments, are extremely exciting," said team member Maria Nielsdottir: "They provide strong evidence that low iron availability limits summer biological production in the high-latitude North Atlantic. This has only previously been suspected, but helps explain why the spring phytoplankton bloom does not continue well into the summer and why residual amounts of nitrate remain unused."

The central Iceland Basin receives little iron input from continental sources or from atmospheric dust, and some iron is also lost through detrital sinking. Moreover, the new findings suggest that iron brought to the surface during winter overturning is insufficient to support maintenance of the phytoplankton bloom into the summer.

Nielsdottir, a research student at the University of Southampton's School of Ocean and Earth Science based at the National Oceanography Centre, said: "In effect, the high-latitude North Atlantic is a seasonal HNLC region, whereas classic, HNLC regions such as the Southern Ocean remain in this condition throughout the year."

The failure of the phytoplankton community to exploit residual nitrate remaining in the summer reduces the effectiveness of the biological carbon pump. "This is important," says Nielsdottir, "because the high-latitude North Atlantic is second only to the Southern Ocean in its potential to lower atmospheric carbon dioxide and un used nitrate in the surface highlight the potential for even higher CO₂ drawdown, high levels of which are an important cause of global climate warming."

The work was supported by the National Oceanography Centre with a PhD to MCN, Natural Environment Research Council, Oceans2025 and the Faroese Ministry of Interior and Law. The authors are Maria Nielsdottir, C. Mark Moore, Richard Sanders, Daria Hinz and Eric Achterberg, University of Southampton's School of Ocean and Earth Science based at the National Oceanography Centre, Southampton.

Snows Of Kilimanjaro Shrinking Rapidly, And Likely To Be Lost

2009-11-04T06:26:00.000-08:00

The remaining ice fields atop famed Mount Kilimanjaro in Tanzania could be gone within two decades and perhaps even sooner, based on the latest survey of the ice fields remaining on the mountain .

The findings indicate a major cause of this ice loss is very likely to be the rise in global temperatures. Although changes in cloudiness and precipitation may also play a role, they appear less important, particularly in recent decades.

The first calculation of ice volume loss indicates that from 2000 to 2007, the loss by thinning is now roughly equal to that by shrinking.

These predictions, published in the journal Proceedings of the National Academy of Sciences, are among the latest dramatic physical evidence of global climate change.

Paleoclimatologist Lonnie Thompson, professor of earth sciences at Ohio State University, and his colleagues amassed a trail of data showing the rapid loss of ice atop Africa's highest mountain:

85 percent of the ice that covered the mountain in 1912 had been lost by 2007, and 26 percent of the ice there in 2000 is now gone;

A radioactive signal marking the 1951-52 "Ivy" atomic tests that was detected in 2000 1.6 meters (5.25 feet) below the surface of the Kilimanjaro ice is now lost, with an estimated 2.5 meters (8.2 feet) missing from the top of the current ice fields;

The presence of elongated bubbles trapped in the frozen ice at the top of one of the cores shows that surface ice has melted and refrozen. There is no evidence of sustained melting anywhere in the rest of the core that dates back 11,700 years;

Even 4,200 years ago, a drought in that part of Africa that lasted about 300 years and left a thick (about 1-inch) dust layer, was not accompanied by any evidence of melting. These observations confirm that the current climate conditions over Mount Kilimanjaro are unique over the last 11 millennia.

"This is the first time researchers have calculated the volume of ice lost from the mountain's ice fields," said Thompson, a research scientist with Ohio State's Byrd Polar Research Center. "If you look at the percentage of volume lost since 2000 versus the percentage of area lost as the ice fields shrink, the numbers are very close."

While the loss of mountain glaciers is most apparent from the retreat of their margins, Thompson said an equally troubling effect is the thinning of the ice fields from the surface.

The summits of both the Northern and Southern Ice Fields atop Kilimanjaro have thinned by 1.9 meters (6.2 feet) and 5.1 meters (16.7 feet) respectively. The smaller Furtwangler Glacier, which was melting and water-saturated in 2000 when it was drilled, has thinned as much as 50 percent between 2000 and 2009.

"It has lost half of its thickness," Thompson explained. "In the future, there will be a year when Furtwängler is present and by the next year, it will have disappeared . The whole thing will be gone!"

Thompson's team drilled six cores through Kilimanjaro's ice fields in 2000 and published their findings in the journal Science two years later. That work established a detailed baseline against which more recent data can be compared.

Thompson said the changes occurring on Mount Kilimanjaro mirror those on Mount Kenya and the Rwenzori Mountains in Africa, as well as tropical glaciers high in the South American Andes and in the Himalayas.

"The fact that so many glaciers throughout the tropics and subtropics are showing similar responses suggests an underlying common cause. The increase of Earth's near surface temperatures, coupled with even greater increases in the mid- to upper-tropical troposphere, as documented in recent decades, would at least partially explain the observed widespread similarity in glacier behavior," he said.

Along with Thompson, Ellen Mosley-Thompson, Henry Brecher and Bryan Mark, all with the Byrd Polar Research Center, and Douglas Hardy from the University of Massachusetts all contributed to the study.

The research was sponsored primarily by the Paleoclimate Program of the National Science Foundation with additional support from the Climate, Water and Carbon (CWC) Program at Ohio State University.

African Desert Rift Confirmed As New Ocean In The Making

2009-11-04T06:25:00.000-08:00

In 2005, a gigantic, 35-mile-long rift broke open the desert ground in Ethiopia. At the time, some geologists believed the rift was the beginning of a new ocean as two parts of the African continent pulled apart, but the claim was controversial.

Now, scientists from several countries have confirmed that the volcanic processes at work beneath the Ethiopian rift are nearly identical to those at the bottom of the world's oceans, and the rift is indeed likely the beginning of a new sea.

The new study, published in the latest issue of Geophysical Research Letters, suggests that the highly active volcanic boundaries along the edges of tectonic ocean plates may suddenly break apart in large sections, instead of little by little as has been predominantly believed. In addition, such sudden large-scale events on land pose a much more serious hazard to populations living near the rift than would several smaller events, says Cindy Ebinger, professor of earth and environmental sciences at the University of Rochester and co-author of the study.

"This work is a breakthrough in our understanding of continental rifting leading to the creation of new ocean basins," says Ken Macdonald, professor emeritus in the Department of Earth Science at the University of California, Santa Barbara, and who is not affiliated with the research. "For the first time they demonstrate that activity on one rift segment can trigger a major episode of magma injection and associated deformation on a neighboring segment. Careful study of the 2005 mega-dike intrusion and its aftermath will continue to provide extraordinary opportunities for learning about continental rifts and mid-ocean ridges."

"The whole point of this study is to learn whether what is happening in Ethiopia is like what is happening at the bottom of the ocean where it's almost impossible for us to go," says Ebinger. "We knew that if we could establish that, then Ethiopia would essentially be a unique and superb ocean-ridge laboratory for us. Because of the unprecedented cross-border collaboration behind this research, we now know that the answer is yes, it is analogous."

Atalay Ayele, professor at the Addis Ababa University in Ethiopia, led the investigation, painstakingly gathering seismic data surrounding the 2005 event that led to the giant rift opening more than 20 feet in width in just days. Along with the seismic information from Ethiopia, Ayele combined data from neighboring Eritrea with the help of Ghebrebrhan Ogubazghi, professor at the Eritrea Institute of Technology, and from Yemen with the help of Jamal Sholan of the National Yemen Seismological Observatory Center. The map he drew of when and where earthquakes happened in the region fit tremendously well with the more detailed analyses Ebinger has conducted in more recent years.

Ayele's reconstruction of events showed that the rift did not open in a series of small earthquakes over an extended period of time, but tore open along its entire 35-mile length in just days. A volcano called Dabbahu at the northern end of the rift erupted first, then magma pushed up through the middle of the rift area and began "unzipping" the rift in both directions, says Ebinger.

Since the 2005 event, Ebinger and her colleagues have installed seismometers and measured 12 similar -- though dramatically less intense -- events.

"We know that seafloor ridges are created by a similar intrusion of magma into a rift, but we never knew that a huge length of the ridge could break open at once like this," says Ebinger. She explains that since the areas where the seafloor is spreading are almost always situated under miles of ocean, it's nearly impossible to monitor more than a small section of the ridge at once so there's no way for geologists to know how much of the ridge may break open and spread at any one time. "Seafloor ridges are made up of sections, each of which can be hundreds of miles long. Because of this study, we now know that each one of those segments can tear open in a just a few days."

Ebinger and her colleagues are continuing to monitor the area in Ethiopia to learn more about how the magma system beneath the rift evolves as the rift continues to grow.

Additional authors of the study include Derek Keir, Tim Wright, and Graham Stuart, professors of earth and environment at the University of Leeds, U.K.; Roger Buck, professor at the Earth Institute at Columbia University, N.Y.; and Eric Jacques, professor at the Institute de Physique du Globe de Paris, France.

Deep-sea Ecosystems Affected By Climate Change

2009-11-04T06:22:00.000-08:00

The vast muddy expanses of the abyssal plains occupy about 60 percent of the Earth's surface and are important in global carbon cycling. Based on long-term studies of two such areas, a new paper in the Proceedings of the National Academy of Sciences (PNAS) shows that animal communities on the abyssal seafloor are affected in a variety of ways by climate change.

Historically, many people, including marine scientists, have considered the abyssal plains, more than 2,000 meters below the sea surface, to be relatively isolated and stable ecosystems. However, according to Ken Smith, a marine ecologist at the Monterey Bay Aquarium Research Institute (MBARI) and lead author of the recent PNAS article, changes in the Earth's climate can cause unexpectedly large changes in deep-sea ecosystems. Based on 18 years of studies, Smith and his coauthors show that such ecosystem changes occur over short time scales of weeks to months, as well as over longer periods of years to decades.

The recent paper covers two time-series studies -- one at "Station M," about 220 kilometers off the Central California coast, and a second on the Porcupine Abyssal Plain, several hundred kilometers southwest of Ireland. The flat, muddy seafloor at these sites lies between 4,000 and 5,000 meters beneath the ocean surface.

In this cold, dark environment, very little food is available. What food there is takes the form of bits of organic debris drifting down from the sunlit surface waters, thousands of meters above. During its long descent, this organic matter may be eaten, excreted, and decomposed, drastically reducing its nutritive value. It is estimated that less than five percent of the organic matter produced at the surface reaches the abyssal plains.

Research by Smith and his coauthors has shown that the amount of food reaching the deep sea varies dramatically over time. For example, at the Porcupine Abyssal Plain, the amount of organic material sinking from above can vary by almost an order of magnitude from one year to another.

Such variations in food supply have several causes. On a seasonal basis, algal blooms near the sea surface send pulses of organic material to the deep seafloor. Other factors may also come into play, including how much of the algae is eaten by marine animals, and how the material is moved by ocean currents.

The authors point out that global climate change could affect the food supply to the deep sea in many ways. Some relevant ocean processes that may be affected by climate change include wind-driven upwelling, the depth of mixing of the surface waters, and the delivery of nutrients to surface waters via dust storms. Climate-driven changes in these processes are likely to lead to altered year-to-year variation in the amount of organic material reaching the seafloor.

As one example of ongoing changes in deep-sea ecosystems, the authors point to the fact that one of the most important groups of fish on the deep seafloor, the grenadiers, doubled in abundance between 1989 and 2004 at Station M. They speculate that change may be linked to a combination of climate change and commercial fishing.

In another example, some previously common species of sea cucumbers at Station M virtually disappeared after 1998, while others became much more abundant. These changes were tied to a significant El Niño event in 1997-98. Similar dramatic year-to-year changes were observed at Porcupine Abyssal Plain, where they were linked to changes in both the quantity and type of food reaching the seafloor.

Based on their observations, the authors conclude that long-term climate change is likely to influence both deep-sea communities and the chemistry of their environment. According to Smith, "Essentially, deep-sea communities are coupled to surface production. Global change could alter the functioning of these ecosystems and the way carbon is cycled in the ocean."

Changes in deep-sea carbon cycling are not considered in most climate models, an oversight that the authors believe should be corrected. In order to obtain the information needed to include seafloor-community changes in global climate models, the authors suggest that long-term, automated systems must be developed for monitoring the deep sea.

Smith and his colleagues point out that deep-sea ecosystems are prime targets for monitoring using cabled ocean observatories, new seafloor moorings, and robots, which can provide continuous data to capture both long-term and short-term changes in seafloor conditions. As coauthor Henry Ruhl put it, "What we need is to move beyond fragmented research programs and transition to a comprehensive global effort to monitor deep-sea ecosystems."

The research at Station M was sponsored by grants from the National Science Foundation and the David and Lucile Packard Foundation. Research at the Porcupine Abyssal Plain Sustained Observatory site was supported by the European Union and the Natural Environment Research Council of the United Kingdom.

North Carolina Sea Levels Rising Three Times Faster Than In Previous 500 Years, Study Finds

2009-11-01T06:56:00.000-08:00

An international team of environmental scientists led by the University of Pennsylvania has shown that sea-level rise, at least in North Carolina, is accelerating. Researchers found 20th-century sea-level rise to be three times higher than the rate of sea-level rise during the last 500 years. In addition, this jump appears to occur between 1879 and 1915, a time of industrial change that may provide a direct link to human-induced climate change.

The results appear in the current issue of the journal Geology.
The rate of relative sea-level rise, or RSLR, during the 20th century was 3 to 3.3 millimeters per year, higher than the usual rate of one per year. Furthermore, the acceleration appears consistent with other studies from the Atlantic coast, though the magnitude of the acceleration in North Carolina is larger than at sites farther north along the U.S. and Canadian Atlantic coast and may be indicative of a latitudinal trend related to the melting of the Greenland ice sheet.
Understanding the timing and magnitude of this possible acceleration in the rate of RSLR is critical for testing models of global climate change and for providing a context for 21st-century predictions.
"Tide gauge records are largely inadequate for accurately recognizing the onset of any acceleration of relative sea-level rise occurring before the 18th century, mainly because too few records exist as a comparison," Andrew Kemp, the paper's lead author, said. "Accurate estimates of sea-level rise in the pre-satellite era are needed to provide an appropriate context for 21st-century projections and to validate geophysical and climate models."
The research team studied two North Carolina salt marshes that form continuous accumulations of organic sediment, a natural archive that provides scientists with an accurate way to reconstruct relative sea levels using radiometric isotopes and stratigraphic age markers. The research provided a record of relative sea-level change since the year 1500 at the Sand Point and Tump Point salt marshes in the Albemarle-Pamlico estuarine system of North Carolina. The two marshes provided an ideal setting for producing high-resolution records because thick sequences of high marsh sediment are present and the estuarine system is microtidal, which reduces the vertical uncertainty of aleosea-level estimates. The study provides for the first time replicated sea-level reconstructions from two nearby sites.
In addition, comparison with 20th-century tide-gauge records validates the use of this approach and suggests that salt-marsh records with decadal and decimeter resolution can supplement tide-gauge records by extending record length and compensating for the strong spatial bias in the global distribution of longer instrumental records.
The study was funded by the National Oceanic and Atmospheric Administration Coastal Ocean Program, North Carolina Coastal Geology Cooperative Program, U.S. Geological Survey and National Science Foundation.
The study was conducted by Kemp and Benjamin P. Horton of the Sea-Level Research Laboratory at Penn, Stephen J. Culver and D. Reide Corbett of the Department of Geological Sciences at East Carolina University, Orson van de Plassche of Vrije Universiteit, W. Roland Gehrels of the University of Plymouth, Bruce C. Douglas of Florida International University and Andrew C. Parnell of University College Dublin.

Why Is The Ocean Salty?

2009-11-01T06:49:00.000-08:00

The saltiness of the sea comes from dissolved minerals, especially sodium, chlorine, sulfur, calcium, magnesium, and potassium, says Galen McKinley, a UW-Madison professor of atmospheric and oceanic sciences.

Today’s ocean salt has ancient origins. As the earth formed, gases spewing from its interior released salt ions that reached the ocean via rainfall or land runoff.
Now, the ocean’s salinity is basically constant. “Ions aren’t being removed or supplied in an appreciable amount,” McKinley says. “The removal and sources that do exist are so small and the reservoir is so large that those ions just stay in the water.” For example, she says, “Each year, runoff from the land adds only 0.00005 percent of total ocean salts.”
In lakes, relatively rapid turnover of water and its dissolved salts keeps the water fresh – a water droplet and its ions will stay in Lake Superior for about 200 years, compared to roughly 100 to 200 million years in the ocean. “Even if you did have any accumulation of an ion in a lake, it would be washed out quickly,” McKinley explains.
Ocean salts, however, have no place to go. “The ions that were put there long ago have managed to stick around,” McKinley says. “There is geologic evidence that the saltiness of the water has been the way that it is for at least a billion years

New Wrinkle In Ancient Ocean Chemistry

2009-11-01T06:42:00.000-08:00

Scientists widely accept that around 2.4 billion years ago, the Earth's atmosphere underwent a dramatic change when oxygen levels rose sharply. Called the "Great Oxidation Event" (GOE), the oxygen spike marks an important milestone in Earth's history, the transformation from an oxygen-poor atmosphere to an oxygen-rich one paving the way for complex life to develop on the planet.
Two questions that remain unresolved in studies of the early Earth are when oxygen production via photosynthesis got started and when it began to alter the chemistry of Earth's ocean and atmosphere.
Now a research team led by geoscientists at the University of California, Riverside corroborates recent evidence that oxygen production began in Earth's oceans at least 100 million years before the GOE, and goes a step further in demonstrating that even very low concentrations of oxygen can have profound effects on ocean chemistry.
To arrive at their results, the researchers analyzed 2.5 billion-year-old black shales from Western Australia. Essentially representing fossilized pieces of the ancient seafloor, the fine layers within the rocks allowed the researchers to page through ocean chemistry's evolving history.
Specifically, the shales revealed that episodes of hydrogen sulfide accumulation in the oxygen-free deep ocean occurred nearly 100 million years before the GOE and up to 700 million years earlier than such conditions were predicted by past models for the early ocean. Scientists have long believed that the early ocean, for more than half of Earth's 4.6 billion-year history, was characterized instead by high amounts of dissolved iron under conditions of essentially no oxygen.
"The conventional wisdom has been that appreciable atmospheric oxygen is needed for sulfidic conditions to develop in the ocean," said Chris Reinhard, a Ph.D. graduate student in the Department of Earth Sciences and one of the research team members. "We found, however, that sulfidic conditions in the ocean are possible even when there is very little oxygen around, below about 1/100,000th of the oxygen in the modern atmosphere."
Reinhard explained that at even very low oxygen levels in the atmosphere, the mineral pyrite can weather on the continents, resulting in the delivery of sulfate to the ocean by rivers. Sulfate is the key ingredient in hydrogen sulfide formation in the ocean.
Timothy Lyons, a professor of biogeochemistry, whose laboratory led the research, explained that the hydrogen sulfide in the ocean is a fingerprint of photosynthetic production of oxygen 2.5 billion years ago.
"A pre-GOE emergence for oxygenic photosynthesis is a matter of intense debate, and its resolution lies at the heart of understanding the evolution of diverse forms of life," he said. "We have found an important piece of that puzzle."
Study results appear in the Oct. 30 issue of Science.
"Our data point to oxygen-producing photosynthesis long before concentrations of oxygen in the atmosphere were even a tiny fraction of what they are today, suggesting that oxygen-consuming chemical reactions were offsetting much of the production," said Reinhard, the lead author of the research paper.
The researchers argue that the presence of small amounts of oxygen may have stimulated the early evolution of eukaryotes -- organisms whose cells bear nuclei -- millions of years prior to the GOE.
"This initial oxygen production set the stage for the development of animals almost two billion years later," Lyons said. "The evolution of eukaryotes had to take place first."
The findings also have implications for the search for life on extrasolar planets.
"Our findings add to growing evidence suggesting that biological production of oxygen is a necessary but not sufficient condition for the evolution of complex life," Reinhard said. "A planetary atmosphere with abundant oxygen would provide a very promising biosignature. But one of the lessons here is that just because spectroscopic measurements don't detect oxygen in the atmosphere of another planet doesn't necessarily mean that no biological oxygen production is taking place."
To analyze the shales, Reinhard first pulverized them into a fine powder in Lyons's laboratory. Next, the powder was treated with a series of chemicals to extract different minerals. The extracts were then run on a mass-spectrometer at UC Riverside.
"One exciting thing about our discovery of sulfidic conditions occurring before the GOE is that it might shed light on ocean chemistry during other periods in the geologic record, such as a poorly understood 400 million-year interval between the GOE and around 1.8 billion years ago, a point in time when the deep oceans stopped showing signs of high iron concentrations," Reinhard said. "Now perhaps we have an explanation. If sulfidic conditions could occur with very small amounts of oxygen around, then they might have been even more common and widespread after the GOE."
Said Lyons, "This is important because oxygen-poor and sulfidic conditions almost certainly impacted the availability of nutrients essential to life, such as nitrogen and trace metals. The evolution of the ocean and atmosphere were in a cause-and-effect balance with the evolution of life."
Reinhard and Lyons were joined in the research by Clint Scott of UCR; Ariel Anbar of the Arizona State University, Tempe; and Rob Raiswell of the University of Leeds, United Kingdom

First Detailed Documentation Of Tsunami Erosion

2009-10-31T06:56:00.000-07:00

Tsunamis are among the most-devastating natural calamities. These earthquake-generated waves can quickly engulf low-lying land and bring widespread destruction and death. They can deposit sand and debris far inland from where they came ashore.

Now, for the first time, a group of scientists working in the Kuril Islands off the east coast of Russia has documented the scope of tsunami-caused erosion and found that a wave can carry away far more sand and dirt than it deposits.

The fortuitous observations resulted because the Kuril Biocomplexity Project had made detailed surveys of some Kuril Island coastlines during the summer of 2006, and then returned for additional work in the summers of 2007 and 2008. That provided a unique opportunity for before-and-after comparisons following a magnitude 8.3 earthquake and accompanying tsunami on Nov. 15, 2006, and an 8.1 quake and resulting tsunami on Jan. 13, 2007.

When the scientists revisited coastlines they had surveyed in 2006, they found that in some places the amount of sand and soil removed by tsunami erosion was nearly 50 times greater than the amount deposited.

"It was so extreme. I was really surprised," said Breanyn MacInnes, a University of Washington doctoral student in Earth and space sciences.

The team observed shorelines stripped of vegetation, small hills of soil and volcanic cinders washed away to expose boulders and, in one place, the unearthed rusty remnants of military equipment left behind at the end of World War II.

"We were there the year before and it had been completely covered with vegetation, and there were ridges closer to shore that had been completely removed when we returned," MacInnes said.

She is the lead author of a paper describing the observed differences in erosion and deposition, published in the November issue of the journal Geology. Co-authors are Joanne Bourgeois, a UW professor of Earth and space sciences and MacInnes' doctoral adviser, and Tatiana Pinegina and Ekaterina Kravchunovskaya of the Far East Branch of the Russian Academy of Sciences. The work was funded by the National Science Foundation and the Russian Academy of Sciences Institute of Marine Geology and Geophysics.

The Nov. 15, 2006, Kurils earthquake was large enough to raise alarms about the potential for a tsunami throughout the Pacific basin. Only very tiny waves were recorded on the Japanese island of Hokkaido, relatively near the Kurils. However, a tsunami nearly 6 feet high did more than $10 million damage to the harbor at Crescent City, Calif., some 4,500 miles away.

The Kurils themselves were hit by tsunami waves more than 70 feet high in some places, and changes in topography were dramatic.

The amount of erosion from a tsunami depends somewhat on the topography of the land, but definitely is related to the force of the wave, the scientists found. They noted that an area called South Bay on Matua Island lost about 50 cubic meters, or about 1,765 cubic feet, of sediment per meter of width, while an area called Ainu Bay lost an astounding 200 cubic meters, or about 7,060 cubic feet, of sediment per meter of width because of tsunami-induced erosion.

At a spot called Dushnaya Bay, where the tsunami was at a relatively low elevation at its greatest distance from shore, the biggest change occurred on the sandy beach, with about 5 cubic meters, or about 177 cubic feet, of sediment eroded per meter of width.

In other areas, relatively fine volcanic sand from the shore and much coarser volcanic cinders unearthed from ridges were deposited well inland, but the amount of sediment deposited was far less than the amount eroded, the researchers found.

Some of the landscape scars will remain visible for decades, or even centuries, the scientists reported. For example, along Ainu Bay ridges were removed, depressions were scoured into the topography and a lake was breached and drained.

"One thing we really noticed was that anywhere there had been human disturbance, like the remnants of a military base or even just a fencepost, there was always some sort of blowout or deeper erosion," MacInnes said.

She noted that geologists have long considered erosion to be an important factor in studying tsunamis.

"There are a lot of papers that describe erosion but they can't really quantify it. Our study is the first to say, 'This much sand was removed from the coast,'" she said.

"This emphasizes that erosion is something to consider when assessing a community's risks and vulnerability."

Skull Of Crocodile 100 Million Years Old Unearthed

2009-10-31T06:52:00.000-07:00

Paleontologists have made the most important discovery to date at the Arlington Archosaur Site, a prolific fossil site in North Arlington, Texas. The disassembled skull of a crocodile with two and a half inch long teeth that lived nearly 100 million years ago has been unearthed.

"We have over 50 bones exposed," said The University of Texas at Arlington dinosaurs lecturer Derek Main, who heads the project. "They are truly impressive. The teeth measure 6.5 centimeters, larger than my thumb."

To date, more dinosaur fossils have been recovered from the Arlington Archosaur Site, where excavation began little more than a year ago, than from any other site in the Dallas-Fort Worth area. The site lies within Cretaceous rocks, formed 95 million years ago when Arlington was the beachhead for a giant sea that divided the continent.

The site has yielded fossils from various species of animals, including dinosaurs. A skeleton of a large herbivorous "duck billed" dinosaur was excavated from the northern hillside at the site. Crocodile fossils are among the most commonly found.

Main said the site is unique because it is a major dinosaur excavation in the middle of a large metropolitan setting and it preserves many fossils from different animals. he site also has fossils from turtles, lungfish, fish and sharks. The excavation of the Arlington Archosaur Site began in the spring of 2008 when the Huffines Group obtained the property and granted land access to UT Arlington.

Newly Discovered Ankylosaur Dinosaur Is 'Biological Version Of An Army Tank'

2009-10-31T06:44:00.000-07:00

A husband and wife team of American paleontologists has discovered a new species of dinosaur that lived 112 million years ago during the early Cretaceous of central Montana.

The new dinosaur, a species of ankylosaur, is documented in the October issue of the Canadian Journal of Earth Sciences. Ankylosaurs are the biological version of an army tank. They are protected by a plate-like armour with two sets of sharp spikes on each side of the head, and a skull so thick that even 'raptors' such as Deinonychus could leave barely more than a scratch.

Bill and Kris Parsons, Research associates of the Buffalo Museum of Science, found much of the skull of the newly describedTatankacephalus cooneyorumresting on the surface of a hillside in 1997. Because the skull was 90% complete, it was possible to justify this fossil as a new species.

"This is the first member of Ankylosauridae to be found within the Early Cretaceous Cloverly Geologic Formation," said Bill Parsons, who characterized the fossil as a transitional evolutionary form between the earlier Jurassic ankylosaurs and the better known Late Cretaceous ankylosaurs.

The skull is heavily protected by two sets of lateral horns, two thick domes at the back, and smaller thickenings around the nasal region. "Heavy ornamentation and horn-like plates would have covered most of the dorsal surface of this dinosaur" said Bill Parsons.

"For years, Bill and Kris have been collecting fossils from a critical time in Earth's history, and their hard work has paid off," said Lawrence Witmer, professor of paleontology at Ohio University who was not involved with this study. "This is a really important find and gives us a clearer view of the evolution of armored dinosaurs. But this is just the first; I'm sure, of what will be a series of important discoveries from this team."

Parsons also illustrated the dermal armour of this new species based on the theory by Museum of the Rockies paleontologist John R. Horner that there was an outer keratinous sheathing on it as found in modern turtle shells and bird beaks. In his new reconstruction, Parsons suggests that Tatankacephalusexhibited complex and colorful patterns rather than the dull appearance suggested in earlier ankylosaur portraits. "According to Horner's theory, many other dinosaurs also had this kind of sheathing and also may have been diversely colored," said Parsons.

As to its name, the broad, short horns on the back of its skull resemble the horns found on a modern buffalo skull andTatankacephalus loosely translates as 'Buffalo head.' Parsons also noted, "of course any further allusions to the city of Buffalo are completely intentional as well