Science News

Revealing the Explosive Heart of Eta Carinae

2010-01-05T19:25:00.003+01:00

Using adaptive optics to remove atmospheric blurring, Gemini Observatory released an image today showing previously hidden forensic secrets at the ballistic core of the Homunculus Nebula, part of the explosive Eta Carinae star system.

The infrared image, revealed at the 215th American Astronomical Society meeting in Washington DC, is a high-resolution view of the complex tendrils and puffs of glowing gas and dust surrounding the violent and convulsive death of an exceptionally massive, short-lived star.

The compelling modern history of Eta Carinae began in April 1843 when the system underwent a huge 20-year outburst that, throughout some of that period, made it the sky’s second brightest stellar object. During the “Great Eruption” astronomers estimate that about 20 times the mass of our Sun was ejected into interstellar space. Today, astronomers study this relatively nearby stellar oddity to help understand the late evolution of massive stars – a messy process involving outflows, eruptions, strong magnetic fields and powerful jets. The result of this activity is reflected in the new Gemini image presented by John Martin of the University of Illinois Springfield who, along with an international team of researchers, obtained their data using the Near-Infrared Coronagraphic Imager (NICI) at the Gemini South telescope in Chile.

Martin’s team used NICI to study gas and dust features surrounding the central star where the complex structure includes an intricate network of wispy clouds, inspiring the “Butterfly Nebula” moniker. The data also uncover a feature never directly imaged before called the Little Homunculus Nebula. “The Homunculus is an evolving corpse of a dying star and most of what we see is the visible outer layer, like a skin, from the Great Eruption. The Little Homunculus is under that skin,” said Martin. “The Gemini images have allowed us to perform something akin to an autopsy by peeling away the obscuring, outer dusty skin and giving us a glimpse of what’s inside. In the process we're finding things we have never imaged before and didn't expect. It’s like finding your murder victim has a third lung, an extra liver, or something more exotic hidden away under their skin!” Martin and his team hope that these observations will soon trace the uncertain history of a minor eruption in the Eta Carinae system in the late 1890s. The research team also includes Etienne Artigau (University of Montréal, Canada, lead author on subsequent paper and previously at Gemini South), Kris Davidson (University of Minnesota), Roberta Humphreys (University of Minnesota), Olivier Chesneau (FIZEAU, France), and Nathan Smith (University of California).

Eta Carinae, located only about 7,500-8,000 light years away, consists of at least two stars at its core, the largest of which is among the most luminous and massive stars in our galaxy having a mass of at least 100 times that of our sun. The stellar component is visible to the naked eye from the southern hemisphere and very low northern latitudes. Because of the complexity and advanced age of this stellar system, Eta Carinae has displayed consistently odd behavior and its brightness has varied greatly over the centuries. During its massive explosion (that lasted from 1843 through the 1850’s) it gave off as much light energy as a typical supernova but somehow survived the normally annihilating event. What we see as the Homunculus Nebula are the remains of that explosion–sometimes called the supernova imposter event. The gasses expelled from this explosion are hurtling outward at up to 2 million kilometers per hour and are comprised of a mixture of diverse elements (from nitrogen to iron) formed by the massive star.

NICI, the Gemini South instrument used to obtain the data for this result, incorporates a built-in curvature-sensing adaptive optics system and is optimized for the detection of faint, sub-stellar companions. It images over a field of about 18 arcseconds from 1 – 5 microns. In addition to images like the one featured in this release, NICI is currently being utilized in an aggressive planet-finding campaign targeting about 300 nearby stars for possible planetary companions.

Looks Can Be Deceiving

2010-01-02T13:53:00.004+01:00

Does it matter if nature solves the same problem multiple ways? A NSF-supported study of lizard populations in White Sands, New Mexico has helped researcher Erica Rosenblum of the University of Idaho begin to answer that question. Published December 28 in the Proceedings of the National Academy of Sciences, the article describes genetic differences between lizards found in habitats that contain white or dark soils. These stark differences in color are an ideal environment to study natural selection and gene flow.

In three separate lizard species, Rosenblum and her team identified mutations in the gene encoding the melanocortin-1 receptor (Mc1r), all resulting in lizards with light skin. Further biochemical characterization of the mutations revealed that, although the same gene is affected in two of the species, the functional changes caused by the mutations were distinct. In one species the receptor is in the wrong location in the cell, while in a different species the receptor is in the correct location, but it is unable to transmit signal.

"The mutations we observed resulted in two distinct changes in how the Mc1 receptor functioned. Mc1r acts like a light switch for melanin, so even though the way the signaling is disrupted is different, outwardly we see the same result: light-skinned lizards," Rosenblum explained.

Although the end point, light skin, is the same, the different ways the reptiles achieve this have important implications for gene flow in each species. For instance, the dominance pattern of the mutated genes is different in the two species. The mutation that results in improperly located Mc1r protein is dominant, meaning it takes only one copy of the new gene to result in light-skinned lizards. In contrast, the lizards that appear white due to faulty receptor signal transmission must harbor two copies of the mutant gene because the trait is recessive.

Rosenblum added, "There is preliminary evidence that suggests the genes involved in adaptation can also affect speciation. Changes in melanin affect coloration on the top of the body, which predators see, and also the sides of the body, which other lizards use to decide who to mate with. Therefore both natural selection and sexual selection appear to play a role in this system."

This habitat provides researchers the unique opportunity to observe natural selection and speciation in progress. New species can form relatively quickly (over a few thousand years) in some selection environments, but catching organisms in the act is rare. The more researchers understand the speciation process, the better equipped we will be to try to preserve this process as our landscape changes.

Marine Scientists Discover Deepest Undersea Erupting Volcano

2010-01-02T13:47:00.002+01:00

Scientists funded by the National Science Foundation (NSF) and NOAA have recorded the deepest erupting volcano yet discovered --West Mata Volcano-- describing high-definition video of the undersea eruption as "spectacular."

"For the first time we have been able to examine, up close, the way ocean islands and submarine volcanoes are born," said Barbara Ransom, program director in NSF's Division of Ocean Sciences. "The unusual primitive compositions of the West Mata eruption lavas have much to tell us."

The volcanic eruption, discovered in May, is nearly 4,000 feet below the surface of the Pacific Ocean, in an area bounded by Fiji, Tonga and Samoa.

"We found a type of lava never before seen erupting from an active volcano, and for the first time observed molten lava flowing across the deep-ocean seafloor," said the expedition's chief scientist Joseph Resing, a chemical oceanographer at the University of Washington.

"It was an underwater Fourth of July, a spectacular display of fireworks nearly 4,000 feet deep," said co-chief scientist Bob Embley, a marine geologist at NOAA's Pacific Marine Environmental Laboratory in Newport, Ore.

"Since the water pressure at that depth suppresses the violence of the volcano's explosions, we could get an underwater robot within feet of the active eruption. On land, or even in shallow water, you could never hope to get that close and see such great detail."

Imagery includes large molten lava bubbles three feet across bursting into cold seawater, glowing red vents exploding lava into the sea, and the first-observed advance of lava flows across the deep-ocean floor.

Sounds of the eruption were recorded by a hydrophone and later matched with the video footage.

Expedition scientists released the video and discussed their observations at a Dec. 17 news conference at the American Geophysical Union (AGU)'s annual fall meeting in San Francisco.

The West Mata Volcano is producing boninite lavas, believed to be among the hottest on Earth in modern times, and a type seen before only on extinct volcanoes more than one million years old.

University of Hawaii geochemist Ken Rubin believes that the active boninite eruption provides a unique opportunity to study magma formation at volcanoes, and to learn more about how Earth recycles material where one tectonic plate is subducted under another.

Water from the volcano is very acidic, with some samples collected directly above the eruption, the scientists said, as acidic as battery acid or stomach acid.

Julie Huber, a microbiologist at the Marine Biological Laboratory, found diverse microbes even in such extreme conditions.

Tim Shank, a biologist at the Woods Hole Oceanographic Institution (WHOI), found that shrimp were the only animals thriving in the acidic vent water near the eruption. Shank is analyzing shrimp DNA to determine whether they are the same species as those found at seamounts more than 3,000 miles away.

The scientists believe that 80 percent of eruptive activity on Earth takes place in the ocean, and that most volcanoes are in the deep sea.

Further study of active deep-ocean eruptions will provide a better understanding of oceanic cycles of carbon dioxide and sulfur gases, how heat and matter are transferred from the interior of the Earth to its surface, and how life adapts to some of the harshest conditions on Earth.

The science team worked aboard the University of Washington's research vessel Thomas Thompson, and deployed Jason, a remotely-operated vehicle owned by WHOI.

Jason collected samples using its manipulator arms, and obtained imagery using a prototype still and HD imaging system developed and operated by the Advanced Imaging and Visualization Lab at WHOI.

Newly Discovered Dinosaur Illuminates Ancient Lineage

2010-01-02T13:40:00.002+01:00

When Darwin's finches diverged from their common ancestor, the isolation of their island home allowed many species to arise from one.

When their dinosaur ancestors emerged in the Triassic, the island home was the unified landmass Pangea, and the evolution was far more complicated.

In the Dec. 11, 2009, issue of Science, a team of paleontologists introduces the Triassic dinosaur Tawa hallae, an animal that may answer longstanding questions about the earliest years of dinosaur evolution.

The Tawa fossils, collected along with other specimens during recent field excursions to Ghost Ranch in New Mexico, are some of the most complete and best preserved dinosaur skeletons from the Late-Triassic time period.

Tawa possesses features that appear in its contemporaries and features that do not, a finding that helps unite all Triassic carnivorous dinosaurs into one group, the theropods, the same group that included Tyrannosaurus rex, and now includes birds.

The recent finds also support the hypothesis that dinosaurs first originated in what is now South America and soon after diverged into theropods, sauropodomorphs (the line that includes the ground-shaking giants like Apatosaurus) and ornithischians (a line that includes a range of body types, including Stegosaurus and Triceratops).

Only after this divergence did dinosaurs disperse across the Triassic world more than 220 million years ago.

"Tawa gives us an unprecedented window into early dinosaur evolution, solidifying the relationships of early dinosaurs, revealing how they spread across the globe, and providing new insights into the evolution of their characteristics," says Sterling Nesbitt of the University of Texas at Austin, the lead author on the paper.

Nesbitt's co-authors included Nathan Smith of the University of Chicago and the Field Museum of Natural History; Randall Irmis of the Utah Museum of Natural History, University of Utah; 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, where Nesbitt was a researcher at the time of the discovery.

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

Instead, Nesbitt and his colleagues observed three distantly related carnivores in the fossil-rich, Late Triassic beds, implying that each carnivore descended from a separate lineage before arriving in North America, instead of all evolving from a local ancestor. In addition to Tawa, 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 two- to four-meter-long skeletons of Tawa display characteristics that exist in both of its contemporaries, and features found in neither, implying a separate lineage. Unlike many theropods, Tawa's lineage does not lead directly to birds.

According to Nesbitt, the old view held that Herrerasaurus split off of the family tree after the ornithischians, but before the sauropods and theropods diverged. "Tawa now appears to show that the three groups split from each other as soon as dinosaurs evolved," he adds, though paleontologists have not yet found a concrete example of a dinosaur that existed before the divergence.

"Tawa is a very good example of a fossil that fills in what we call a morphological gap," says Nesbitt, referring to a gap in knowledge about how morphology, or body structures, changed over time, a result of the incomplete nature of the fossil record. While theropods were changing quickly in the Triassic, paleontologists have found few animals that preserve the "steps" that define the sequence of changes.

One of the most significant morphological gaps for early dinosaurs lies between Herrerasaurus and animals that are clearly more closely related to birds, such as Coelophysis. According to Nesbitt, Tawa fits perfectly in between. "It is not a missing link," he adds, "It evolved on its own lineage, but it retains characteristics that existed in Herrerasaurus that we thought were more primitive while also possessing features seen in unmistakable theropods, including birds, such as the presence of air sacs surrounding the braincase and neck."

"Usually, early dinosaur specimens are not as complete or well preserved, so they spur a lot more questions than answers," says Nesbitt. "Tawa is so well preserved that every bone we have, we can examine it in three dimensions. And we can analyze five of the skeletons this way, with examples of both mature and immature animals. This is just the tip of the iceberg. All dinosaurs share a common feature, an open hip socket, and you can dissect your Thanksgiving turkey and still see that original feature. But the earliest lineages that lie in between are far from understood."

The Snows of Kilimanjaro: For How Much Longer?

2010-01-02T13:36:00.002+01:00

The iconic snows of Kilimanjaro still exist--but for how long? 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 on the mountain.

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

The findings, by paleoclimatologist Lonnie Thompson at Ohio State University and co-authors, indicate that a major cause of this ice loss is 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 loss of Mount Kilimanjaro's ice cover has attracted worldwide attention because of its impact on regional water resources," said David Verardo, director of NSF's Paleoclimate Program, which funded the research along with Ohio State University's Climate, Water and Carbon Program. "The remaining ice fields are melting from all sides," said Verardo. "Like many glaciers in mid-to-low latitudes, Kilimanjaro's may only be with us for a short time longer."

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

Thompson and colleagues have 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 some 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 tops 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 material which dates back 11,700 years.

•Even 4,200 years ago, a drought in this 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 at 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 scientist at 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 for samples, has thinned as much as 50 percent between 2000 and 2009.

"It has lost half of its thickness," Thompson said. "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," he said.

"The increase of Earth's near-surface temperatures, coupled with even greater such 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."

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

The fossil primate Darwinius and a new find, Afradapis, are not related to humans

2010-01-02T13:30:00.003+01:00

About 40 miles outside Cairo, Egypt, National Science Foundation (NSF)-supported paleontologists from three American universities are revealing features of a newly discovered African primate and solving a riddle about humankind's evolutionary past.

Lead researcher Erik Seiffert of New York's Stony Brook University and his colleagues say their find has the potential to clear up a portion of the human evolutionary tree by resolving the location of a misplaced species.

"The recently described fossil Darwinius, originally recovered from a disused quarry near Messel, Germany in the 1980s, has been widely publicized as an important 'link' in the lineage to higher primates," said Seiffert. He and his research team recently discovered a lemur-like relative of Darwinius in Africa that they named Afradapis and analyzed its place in primate evolution.

"Our study results indicate that Darwinius and its now extinct relatives, including Afradapis, are not in the evolutionary lineage leading to monkeys, apes, and humans as has been debated," he said. "Instead they are more closely related to the living lemurs and lorises."

They report the finding in the October 20 issue of the journal Nature. NSF supports the research through its social, behavioral and economic sciences directorate's physical anthropology program.

Seiffert's team, which includes Jonathan M. G. Perry of Midwestern University, Ill; Elwyn L. Simons of Duke University, N.C. and Doug M. Boyer also of Stony Brook, base their findings on analysis of Afradapis fossils collected from an excavation site modestly called BQ-2 near the Fayum Depression in northern Egypt.

They first discovered a poorly-preserved Afradapis fossil, a fragment that showed features of the front teeth and jaw bone that were almost identical to those of later Old World monkeys. But it didn't make sense to the researchers that a member of that primate lineage would have been present in Africa at such an early time period, about 37 million years ago.

Soon they recovered additional Afradapis fossils and through dental analysis eventually clarified that Afradapis and Darwinius weren't in the line of Old World monkeys, apes and humans, but had concurrently evolved similar features with their distant relative, a type of anthropoid.

"The similar features evolved through the process of convergent evolution," Seiffert explained. "This means that under similar selection pressures, both lineages came to have similar specializations, but these features were not present in their last common ancestor."

Noted shared specializations from dental examinations include fusion of the two halves of the jaw, reduction and loss of the first few premolar teeth, and the presence of front incisors that are each shaped like a spatula, rather than being shaped more like a cone.

Interestingly, the ancestors of Old World monkeys, apes, and humans developed these features millions of years later, long after Afradapis and Darwinius were extinct. But, reconstructing the most likely family tree of both living and extinct primates, taking into consideration virtually all available anatomical evidence, the paleontologists determined that Darwinius, and its relative Afradapis, are not in the direct evolutionary line with humans.

"Our discoveries certainly contribute to a growing body of evidence that indicates that convergent evolution was a common phenomenon in early primate evolution," Seiffert said.

Paleontologists Discover New Fossil Mammal

2010-01-02T13:26:00.003+01:00

Paleontologists in the U.S. and China have discovered a new species of mammal that lived 123 million years ago in what is now the Liaoning Province in China. The newly discovered chipmunk-sized animal, named Maotherium asiaticus, was found in the famous fossil-rich beds of the Yixian Formation in China.

The fossil mammal, reported in this week's issue of the journal Science, offers an important clue to how the mammalian middle ear evolved. It represents an intermediate stage in the evolutionary process of how modern mammals acquired a middle ear structure.

Hearing is an important sensory function for humans, whether for listening to an interesting conversation or to beautiful music, says Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pa., and an author of the Science paper. For mammals as a whole, Luo says, hearing is an evolutionary adaptation vital for survival.

"With a tiny and intricate middle ear structure, mammals have more sensitive hearing in a wider range of sounds than other vertebrates," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences. "This sensitive hearing was crucial for mammals to develop nocturnal adaptations and to survive in dinosaur-dominated times."

The newly discovered ground-living mammal, some five inches long, had teeth with symmetrically arranged cusps specialized for feeding on insects and worms.

By studying this exquisitely preserved fossil, Luo and colleagues believe Maotherium is closely related to marsupials and placentals. What's most surprising, they say, is the animal's ear.

Mammals have highly sensitive hearing, far better than the hearing capacity of all other vertebrates. According to the Chinese and American scientists who discovered the new mammal, the middle ear bones of Maotherium are similar to those of modern mammals.

But unlike modern mammals, Maotherium's middle ear has an unusual connection to its lower jaw.

This connection, also known as the ossified Meckel's cartilage, resembles the embryonic condition of living mammals and the primitive middle ear of pre-mammalian ancestors. These mammal middle ear bones evolved from the bones of the jaw hinge in reptilian relatives.

Paleontologists have long tried to understand the evolutionary pathway through which these precursor jaw-bones became separated from the jaw and moved into the middle ears of modern mammals.

Maotherium asiaticus is a beautifully preserved fossil, one that made it possible for us to reconstruct how the middle ear could be attached to the jaw, says Luo.

Modern biology has shown that genes can trigger the development of unusual middle ear structures like the "re-appearance" of the Meckel's cartilage in modern mice.

The scientists suggest that the unusual middle ear structure found in the Chinese fossil, such as the ossified Meckel's cartilage, is the manifestation of developmental gene mutations in long-ago mammal evolution.

The Science paper is co-authored by paleontologists Qiang Ji of the Chinese Academy of Geological Sciences in Beijing and Xinliang Zhang of the Henan Provincial Geological Museum, along with other collaborators.

The researchers also received support from the National Natural Science Foundation (China), Ministry of Science and Technology (China), and National Geographic Society.

North Meets South? Glaciers Move Together in Far-flung Regions

2010-01-02T13:13:00.002+01:00

Results of a new study add evidence that climate swings in the northern hemisphere over the past 12,000 years have been tightly linked to changes in the tropics.

The findings, published this week in the journal Science, suggest that a prolonged cold spell that caused glaciers in Europe and North America to creep forward several hundred years ago may have affected climate patterns as far south as Peru, causing tropical glaciers there to expand, too.

Glaciers in both the tropics and North Atlantic region reached their most recent maximum extents during the so-called Little Ice Age, about 1650 AD to 1850 AD, according to the scientists conducting the research.

To make the discovery, they employed a cutting-edge technique for dating glacial deposits.

"The results bring us one step closer to understanding global-scale patterns of glacier activity and climate during the Little Ice Age," says lead author Joe Licciardi, a glacial geologist at the University of New Hampshire.

By understanding how glaciers behaved in the past, the geoscientists hope to predict how parts of the world will react as the planet warms.

Human civilization arose during fairly stable temperatures since the end of the last ice age, about 12,000 years ago. But research shows that even during this time glaciers fluctuated in large and sometimes surprising ways.

Most of the world's glaciers are now retreating, as manmade greenhouse gas levels rise.

The Intergovernmental Panel on Climate Change predicts that global temperatures may climb another 1.1 to 6.4 degrees Celsius by this century's end.

"If the current dramatic warming projections are correct, we have to face the possibility that the glaciers may soon disappear," said Joerg Schaefer, a geochemist at Columbia University's Lamont-Doherty Earth Observatory (LDEO) and co-author of the paper.

In a warmer world, regions that depend on glaciers for drinking water, farming and hydropower will need to come up with strategies to adapt.

Recent developments in a technique called surface exposure dating have allowed scientists to place far more precise dates on glacial fluctuations during recent times than was previously possible.

When glaciers advance, they drag rocks and dirt with them. When they recede, ridges of debris called moraines are left behind, and the newly exposed deposits are bombarded by cosmic rays passing through Earth's atmosphere.

The rays react with the rock and over time form tiny amounts of the rare chemical isotope beryllium-10. By measuring the buildup of this isotope in glacial rocks, scientists can calculate when the glaciers receded.

Using this technique, the authors showed that glaciers in southern Peru moved at times similar to those in the northern hemisphere.

"The results are based on the CRONUS-Earth Project, which aims to improve measurements of these isotopes so precise ages may be assigned to 'young' glacial moraines," says Enriqueta Barrera, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

"Through CRONUS-Earth, we hope to create a global map of recent glacial fluctuations."

The global picture is complex. Glaciers in New Zealand's Southern Alps, 7,000 miles southwest of this study area in Peru, for example, expanded and contracted more frequently than northern glaciers, reaching their most recent maximum 6,500 years ago--long before the Little Ice Age.

"If we compare records--New Zealand, Europe, Peru--we can say that the tropical Andes look like Europe but not New Zealand," said Licciardi. "What's emerging is a more complicated picture of recent glaciations."

Licciardi first noticed the glacial deposits in 2003 while he was in Peru on vacation.

Hiking to the ruins of the ancient Inca city of Machu Picchu, he was struck by the massive, well-preserved moraines he encountered along the way.

Two years later, David Lund, a paleoclimatologist at the University of Michigan, hiked the same trail and collected rock samples there, which he sent to Licciardi. "That was the catalyst for turning our ideas into a project," says Licciardi.

Licciardi returned in 2006 to the nearby slopes of Nevado Salcantay, a 20,000-foot-high peak that's the tallest in the Cordillera Vilcabamba range.

Over the next two years, Licciardi and graduate student Jean Taggart, also a co-author of the paper, collected more rock samples from the moraines and analyzed them using the beryllium isotope method, with the help of Schaefer.

The beryllium dating method was pioneered in the 1980s, but only recently has it become precise enough to track the ebb and flow of glaciers over the last thousand years.

"Until the last year or two, we had no way of dating the youngest deposits with this method," said Licciardi." Recent breakthroughs in the technique have allowed this story to emerge."

With Peru's climate now linked to northern Europe's, the scientists plan to expand their research to other parts of the South American tropics. They hope to establish a regional pattern of glacial advances and retreats that can be compared with other places worldwide.

Funding also was provided by UNH, Sigma Xi, and the Geological Society of America.

More to Solar Cycle Than Sunspots

2010-01-02T13:08:00.002+01:00

Challenging conventional wisdom, new research finds that the number of sunspots provides an incomplete measure of changes in the sun's impact on Earth over the course of the 11-year solar cycle. The study, led by scientists at the National Center for Atmospheric Research (NCAR) and the University of Michigan, finds that Earth was bombarded last year with high levels of solar energy at a time when the sun was in an unusually quiet phase and sunspots had virtually disappeared.

"The sun continues to surprise us," says lead author Sarah Gibson of NCAR's High Altitude Observatory. "The solar wind can hit Earth like a fire hose even when there are virtually no sunspots."

The study, also written by scientists at NOAA and NASA, is being published today in the Journal of Geophysical Research. It was funded by NASA and by the National Science Foundation, NCAR's sponsor.

"It is vitally important to realize that the 'quiet' sun really isn't all that quiet," says Rich Behnke, program director in NSF's Division of Atmospheric Sciences. "These high-speed streams of wind can affect many of our communications and navigation systems. And they can come at any time, during any part of the solar cycle."

Scientists for centuries have used sunspots, which are areas of concentrated magnetic fields that appear as dark patches on the solar surface, to determine the approximately 11-year solar cycle. At solar maximum, the number of sunspots peaks. During this time, intense solar flares occur daily and geomagnetic storms frequently buffet Earth, knocking out satellites and disrupting communications networks.

Gibson and her colleagues focused instead on another process by which the sun discharges energy. The team analyzed high-speed streams within the solar wind that carry turbulent magnetic fields out into the solar system.

When those streams blow by Earth, they intensify the energy of the planet's outer radiation belt. This can create serious hazards for Earth-orbiting satellites and affect global communications systems, while also threatening astronauts in the International Space Station. Auroral storms light up the night sky repeatedly at high latitudes as the streams move past, driving mega-ampere electrical currents a few hundred miles above Earth's surface. All that energy heats and expands the upper atmosphere. This expansion pushes denser air higher, slowing down satellites and causing them to drop to lower altitudes.

Scientists previously thought that the streams largely disappeared as the solar cycle reached minimum. But when the study team compared measurements within the current solar minimum interval, taken in 2008, with measurements of the last solar minimum in 1996, they found that the Earth in 2008 was continuing to resonate with the effects of the streams. Although the current solar minimum has fewer sunspots than any minimum in 75 years, the sun's effect on Earth's outer radiation belt, as measured by electron fluxes, was more than three times greater last year than in 1996.

Gibson said that observations this year show that the winds have finally slowed, almost two years after sunspots reached the levels of last cycle's minimum.

The authors note that more research is needed to understand the impacts of these high-speed streams on the planet. The study raises questions about how the streams might have affected Earth in the past when the sun went through extended periods of low sunspot activity, such as a period known as the Maunder minimum that lasted from about 1645 to 1715.

"The fact that Earth can continue to ring with solar energy has implications for satellites and sensitive technological systems," Gibson says. "This will keep scientists busy bringing all the pieces together."

Buffeting Earth with streams of energy

For the new study, the scientists analyzed information gathered from an array of space- and ground-based instruments during two international scientific projects: the Whole sun Month in the late summer of 1996 and the Whole Heliosphere Interval in the early spring of 2008. The solar cycle was at a minimal stage during both the study periods, with few sunspots in 1996 and even fewer in 2008.

The team found that strong, long, and recurring high-speed streams of charged particles buffeted Earth in 2008. In contrast, Earth encountered weaker and more sporadic streams in 1996. As a result, the planet was more affected by the sun in 2008 than in 1996, as measured by such variables as the strength of electron fluxes in the outer radiation belt, the velocity of the solar wind in the vicinity of Earth, and the periodic behavior of auroras (the Northern and Southern lights) as they responded to repeated high-speed streams.

The prevalence of high-speed streams during this solar minimum appears to be related to the current structure of the sun. As sunspots became less common over the last few years, large coronal holes lingered in the surface of the sun near its equator. The high-speed streams that blow out of those holes engulfed Earth during 55 percent of the study period in 2008, compared to 31 percent of the study period in 1996. A single stream of charged particles can last for as long as seven to 10 days. At their peak, the accumulated impact of the streams during one year can inject as much energy into Earth's environment as massive eruptions from the sun's surface can during a year at the peak of a solar cycle, says co-author Janet Kozyra of the University of Michigan.

The streams strike Earth periodically, spraying out in full force like water from a fire hose as the sun revolves. When the magnetic fields in the solar winds point in a direction opposite to the magnetic lines in Earth's magnetosphere, they have their strongest effect. The strength and speed of the magnetic fields in the high-speed streams can also affect Earth's response.

The authors speculate that the high number of low-latitude coronal holes during this solar minimum may be related to a weakness in the sun's overall magnetic field. The sun in 2008 had smaller polar coronal holes than in 1996, but high-speed streams that escape from the sun's poles do not travel in the direction of Earth.

"The sun-Earth interaction is complex, and we haven't yet discovered all the consequences for the Earth's environment of the unusual solar winds this cycle," Kozyra says. "The intensity of magnetic activity at Earth in this extremely quiet solar minimum surprised us all. The new observations from last year are changing our understanding of how solar quiet intervals affect the Earth and how and why this might change from cycle to cycle."

Unraveling the Chemistry of Titan's Hazy Atmosphere

2010-01-02T13:04:00.003+01:00

An international team of scientists has announced the confirmation of a key chemical reaction that forms the molecule triacetylene in the ultra-cold atmosphere of Saturn's moon Titan.

Since Titan's current atmosphere is thought to resemble Earth's early atmosphere, the researchers' study suggests triacetylene may have been formed in Earth's early atmosphere and offers clues to the evolution of Earth's atmosphere before the development of life some 3.5 billion years ago.

The team presents their findings in the Sept. 14, 2009, advance online issue of the Proceedings of the National Academy of Sciences. Funding for the study was provided by the National Science Foundation (NSF).

Triacetylene is member of the polyyne family of compounds. Polyynes are thought to serve as an ultraviolet radiation shield in planetary environments, thus acting as prebiotic ozone, and as important components of the orange-colored and aerosol-based haze shrouding Titan.

Scientists have been researching the role of triacetylene, as well as the polyyne diacetylene, in the chemical evolution of Titan's atmosphere for the last four decades.

Triacetylene and diacetylene are molecules consisting of six and four carbon atoms, respectively, and two hydrogen atoms. The atoms in each molecule are connected by alternating single and triple bonds.

Alas, the underlying chemical processes initiating and controlling the formation and growth of the two polyynes are the least understood to date.

Based on limited laboratory studies related to the formation of soot, early planetary chemists developed photochemical models of Titan's atmosphere.

"Surprisingly, the photochemical models show inconsistent mechanisms for the production of polyynes," said Ralf Kaiser, a physical chemist at the University of Hawaii, co-author and team leader. A mechanism is the sequence of steps in a chemical reaction.

The arrival of the Cassini spacecraft at Titan in 2004, and the landing of its Huygens probe on Titan's surface in 2005, confirmed the abundance of diacetylene and acetylene on Titan. Acetylene is made of two carbon and two hydrogen atoms; the carbon atoms are connected by a triple bond. Triacetylene was also detected in Titan's most outer atmosphere via a positively charged form of triacetylene with an additional hydrogen atom.

The mission also revealed that the transformation of acetylene and diacetylene to polyacetylenes such as triacetylene likely present one of the most fundamental steps in the evolution of planetary atmospheres.

To unravel the formation of triacetylene and provide an accurate photochemical model, Kaiser and his collaborators first confirmed in their earthly laboratory that triacetylene can be formed by a single collision of a "radical" ethynyl molecule and a diacetylene molecule.

Ethynyl is highly reactive and made of two carbon atoms connected by a triple bond, one hydrogen atom connected by a single bond, and a lone electron on the exterior carbon atom. It is the lone or radical electron that initiates ethynyl's attack on other molecules (see third side image).

Ethynyl is produced in Titan's atmosphere by the photodissociation of acetylene by ultraviolet light. Photodissociation is a chemical reaction that uses light's photons to break down a chemical compound.

To conduct the experiment, Kaiser's group used a "crossed molecular beam" machine to collide supersonic gaseous beams of ethynyl and diacetylene molecules. Angular resolved mass spectrometer measurements of the reaction products confirmed that triacetylene, plus a single hydrogen atom, were produced.

To reveal the mechanism involved in the formation of triacetylene, Alexander Mebel, a theoretical chemist at Florida International University, merged the experimental results with theoretical computations of the reaction of ethynyl and diacetylene. Theoretical computations also provide the 3-D distribution of electrons in atoms and thus the overall energy level of a molecule.

Mebel's computations confirmed that triacetylene may be formed from the reaction of a single radical ethynyl molecule colliding with diacetylene and the existence of three transient intermediate molecules.

Perhaps most importantly, since the temperature of Titan's atmosphere ranges from -99 F, or -73 C, to -290 F, or -179 C, which necessitates the need for chemical reactions to release energy, Mebel's computations confirmed that the formation of triacetylene releases energy.

To complete their study, Danie Liang and Yuk Yung, planetary scientists at Taiwan's Academia Sinica and California Institute of Technology (Caltech), respectively, performed photochemical modeling studies of Titan's atmosphere. The models suggest that triacetylene may serve as a building block to form more complex and longer polyynes and produce potential precursors for the aerosol-based layers of haze surrounding Titan.

Using a combined experimental, theoretical and modeling study, "Kaiser and his collaborators have demonstrated a successful approach to solving a complex chemistry problem," said Charles Pibel, a program director in the NSF Division of Chemistry.

Global Warming Causes Outbreak of Rare Algae in Caribbean Corals

2010-01-02T12:57:00.003+01:00

A rare opportunity has allowed a team of scientists 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 to rise.

The team, led by Penn State biologist Todd LaJeunesse, found that a rare species of algae that's tolerant of stressful environmental conditions proliferated in corals at a time when more sensitive algae that usually dwell within the corals were being expelled.

The results will be published in the online version of the journal Proceedings of the Royal Society B on September 9, 2009.

Certain species of algae have evolved over millions of years to live in symbiotic relationships with species of corals. These photosynthetic algae provide the corals with nutrients and energy, while the corals provide the algae with a place to live.

"There is a fine balance between giving and taking in these symbiotic relationships," said LaJeunesse.

Symbiodinium trenchi is normally a rare species of algae in the Caribbean, according to LaJeunesse. "Because the species is apparently tolerant of high or fluctuating temperatures, it was able to take advantage of a 2005 warming event and become more prolific."

Symbiodinium trenchi appears to have saved certain colonies of coral from the damaging effects of unusually warm water.

"As ocean temperatures rise as a result of global warming, we can expect this species to become more common and persistent," said LaJeunesse. "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."

If Symbiodinium trenchi takes from the corals more than it gives back, over time the corals' health will decline.

"'Experiments of nature' provide unique opportunities to discover important new insights," said Michael Mishkind, program director in the National Science Foundation (NSF)'s Division of Integrative Organismal Systems, which funded the research.

"These scientists took advantage of just such an event--with the unexpected discovery that an alternate algal species was waiting in the wings. Whether this 'understudy' helps or hinders its host remains to be determined."

In 2005, sea surface temperatures in the Caribbean 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 corals.

The 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.

By late November, water temperatures had peaked and many corals were bleached.

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 is rarely found in the Caribbean, had increased in frequency by 50 percent or more in coral species that are most sensitive to warm water," said LaJeunesse.

"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. Today the symbioses have mostly recovered to their normal state, and the corals have been repopulated by their typical algal symbionts."

Although Symbiodinium trenchi saved some corals from dying in 2005, LaJeunesse is concerned that the species might not be good for the corals if warming trends continue and Symbiodinium trenchi becomes more common.

"Because Symbiodinium trenchi does not appear to have successfully co-evolved with Caribbean coral species, it may not provide the corals with adequate nutrition," he said.

LaJeunesse plans to further investigate the relationship between Symbiodinium trenchi and Caribbean coral species.

"We're interested in looking at how it behaves in other regions of the world where it's naturally common," he said.

The research also was supported by Florida International University, Penn State University, and the University of the West Indies.

Nearby star should harbor detectable, Earth-like planets

2008-05-02T12:02:00.002+02:00

A rocky planet similar to Earth may be orbiting one of our nearest stellar neighbors and could be detected using existing techniques, according to a new study led by astronomers at the University of California, Santa Cruz.

The closest stars to our Sun are in the three-star system called Alpha Centauri, a popular destination for interstellar travel in works of science fiction. UCSC graduate student Javiera Guedes used computer simulations of planet formation to show that terrestrial planets are likely to have formed around the star Alpha Centauri B and to be orbiting in the "habitable zone" where liquid water can exist on the planet's surface. The researchers then showed that such planets could be observed using a dedicated telescope.

"If they exist, we can observe them," said Guedes, who is the first author of a paper describing the new findings. The paper has been accepted for publication by the Astrophysical Journal.

Coauthor Gregory Laughlin, professor of astronomy and astrophysics at UCSC, said a number of factors converge to make Alpha Centauri B an excellent candidate for finding terrestrial planets. The Doppler detection method, which has revealed the majority of the 228 known extrasolar planets, measures shifts in the light from a star to detect the tiny wobble induced by the gravitational tug of an orbiting planet. Factors that favor the use of this technique for Alpha Centauri B include the brightness of the star and its position in the sky, which gives it a long period of observability each year from the Southern Hemisphere, Laughlin said.

Detecting small, rocky planets the size of Earth is challenging, however, because they induce a relatively small wobble in their host stars. According to Laughlin, five years of observations using a dedicated telescope would be needed to detect an Earth-like planet around Alpha Centauri B.

Coauthor Debra Fischer of San Francisco State University is leading an observational program to intensively monitor Alpha Centauri using the 1.5-meter telescope at the Cerro Tololo Inter-American Observatory in Chile. The researchers hope to detect real planets similar to the ones that emerged in the computer simulations.

"I think the planets are there, and it's worth a try to have a look," Laughlin said.

To study planet formation around Alpha Centauri B, the team ran repeated computer simulations, evolving the system for the equivalent of 200 million years each time. Because of variations in the initial conditions, each simulation led to the formation of a different planetary system. In every case, however, a system of multiple planets evolved with at least one planet about the size of Earth. In many cases, the simulated planets had orbits lying within the habitable zone of the star.

In addition to Guedes, Laughlin, and Fischer, the authors of the paper include UCSC postdoctoral researcher Eugenio Rivera and graduate student Erica Davis, and Elisa Quintana of the SETI Institute. This research was supported by NASA and the National Science Foundation.

UC Santa Cruz

Genetic Sequencing of Protein from T. rex Bone Confirms Dinosaurs' Link to Birds

2008-04-25T18:43:00.002+02:00

Scientists have put more meat on the theory that dinosaurs' closest living relatives are modern-day birds. Molecular analysis, or genetic sequencing, of a 68-million-year-old Tyrannosaurus rex protein from the dinosaur's femur confirms that T. rex shares a common ancestry with chickens, ostriches, and to a lesser extent, alligators.

The dinosaur protein was wrested from a fossil T. rex femur discovered in 2003 by paleontologist John Horner of the Museum of the Rockies; the bone was found in a fossil-rich stretch of land in Wyoming and Montana.

The new research results, published this week in the journal Science, represent the first use of molecular data to place a non-avian dinosaur in a phylogenetic tree, a "tree of life," that traces the evolution of species.

"These results match predictions made from skeletal anatomy, providing the first molecular evidence for the evolutionary relationships of a non-avian dinosaur," says Science paper co-author Chris Organ, a researcher at Harvard University. "Even though we only had six peptides--just 89 amino acids--from T. rex, we were able to establish these relationships."

"Tests of the peptide sequences in T. rex bone fossils have confirmed that newer methods of molecular systematics agree with more traditional methods of taxonomic classification based on morphology, or shapes," says Paul Filmer, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

Paper co-author Mary Schweitzer of North Carolina State University (NCSU) and the North Carolina Museum of Natural Sciences first discovered the soft-tissue preservation in the T. rex bone in 2005.

The current paper builds on work reported in Science last year. In that paper, a team headed by John Asara and Lewis Cantley, both of Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School (HMS), first captured and sequenced tiny pieces of collagen protein from T. rex.

Asara became involved in analysis of the collagen protein because of his expertise in mass spectrometry techniques capable of sequencing minute amounts of protein from human tumors.

For the current work, Organ, Asara and colleagues compared collagen protein from several dozen species. The goal: placing T. rex on the animal kingdom's family tree using molecular evidence.

"Most of the collagen sequence was obtained from protein and genome databases, but we also needed to sequence some critical organisms, including modern alligator and modern ostrich, by mass spectrometry," says Asara.

"We determined that T. rex, in fact, grouped with birds--ostrich and chicken--better than any other organism that we studied," he says. "We also showed that it groups better with birds than modern reptiles, such as alligators and green anole lizards."

While scientists have long suspected that birds, and not more basal reptiles, are dinosaurs' closest living relatives, for years that hypothesis rested largely on morphological similarities in bird and dinosaur skeletons.

The scientists also report that a similar analysis of 160,000- to 600,000-year-old collagen protein sequences derived from a mastodon bone establishes a close phylogenetic relationship between that extinct species and modern elephants.

Organ, Asara, Schweitzer and Cantley's co-authors on the current Science paper are Wenxia Zheng of NCSU and Lisa Freimark of BIDMC.

The research also was funded by the National Institutes of Health, the Paul F. Glenn Foundation and the David and Lucile Packard Foundation.

National Science Foundation (NSF)

Upright Walking Began 6 Million Years Ago

2008-04-09T19:49:00.003+02:00

A shape comparison of the most complete fossil femur (thigh bone) of one of the earliest known pre-humans, or hominins, with the femora of living apes, modern humans and other fossils, indicates the earliest form of bipedalism occurred at least six million years ago and persisted for at least four million years.

William Jungers, Ph.D., of Stony Brook University, and Brian Richmond, Ph.D., of George Washington University, say their finding indicates that the fossil belongs to very early human ancestors, and that upright walking is one of the first human characteristics to appear in our lineage, right after the split between human and chimpanzee lineages. Their findings are published in the March 21 issue of the journal Science.

The research is the first thorough quantitative analysis of the Orrorin tugenensis fossil – a fragmentary piece of femur – which was discovered in Kenya in 2000 by a French research team. Dr. Jungers, Chair of Anatomical Sciences at SBU School of Medicine, and Dr. Richmond, Associate Professor of Anthropology at GWU and a member of GWU’s Center for the Advanced Study of Hominid Paleobiology, completed a multivariate analysis of the proximal femora shape of a young adult O. tugenensis that enabled them to pinpoint the pattern of bipedal gait for this controversial hominin. Their analysis included a large and diverse sample of apes, other early hominins, including Australopithecus, and modern humans of all body sizes.

“This research solidifies the evidence that the human lineage split off as far back as six million years ago, that we share ancestry with Orrorin, and that our ancestors were walking upright at the time,” says Dr. Richmond. “These answers were not clear before this analysis.”

“Our study confirms that as early as six million years ago, basal hominins in Africa were already similar to later australopithecines in their anatomy and inferred locomotor biomechanics,” adds Dr. Jungers. “At the same time, by way of the analysis, we see no special phylogenetic connection between Orrorin and our own genus, Homo.”

In “Orrorin tugenensis Femoral Morphology and the Evolution of Hominin Bipedalism,” the authors articulate that the analysis and morphological comparisons among femora from the fossils showed that O. tugenensis is distinct from those of modern humans and the great apes in having a long, anteroposteriorly narrow neck and wide proximal shaft. Early Homo femora have larger heads and broader necks compared to early hominins. In addition to these features, modern human femora have short necks and mediolaterally narrow shafts.

The challenge ahead, explains Dr. Jungers, is “to identify what precipitated the change from this ancient and successful adaptation of upright walking, and climbing, to our own obligate form of bipedalism.”

The Department of Anatomical Sciences centers on teaching and research in the areas of evolutionary morphology, functional morphology, musculoskeletal biology, and vertebrate paleontology. The department interacts with other departments in the School of Medicine, as well as those in Biological Sciences and the Department of Anthropology, through which the Interdepartmental Doctoral Program in Anthropological Sciences (IDPAS) is administered. The IDPAS faculty brings world-renowned strengths in functional morphology and human evolution.

Stony Brook University

Recovering from a mass extinction

2008-03-18T18:39:00.002+01:00

The full recovery of ecological systems, following the most devastating extinction event of all time, took at least 30 million years, according to new research from the University of Bristol.

About 250 million years ago, at the end of the Permian, a major extinction event killed over 90 per cent of life on earth, including insects, plants, marine animals, amphibians, and reptiles. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. This was the nearest life ever came to being completely wiped out.

Previous work indicates that life bounced back quite quickly, but this was mostly in the form of ‘disaster taxa’ (opportunistic organisms that filled the empty ecospace left behind by the extinction), such as the hardy Lystrosaurus, a barrel-chested herbivorous animal, about the size of a pig.

The most recent research, conducted by Sarda Sahney and Professor Michael Benton at the University of Bristol and published in Proceedings of the Royal Society B this week, indicates that specialised animals forming complex ecosystems, with high biodiversity, complex food webs and a variety of niches, took much longer to recover.

Sahney said: “Our research shows that after a major ecological crisis, recovery takes a very long time. So although we have not yet witnessed anything like the level of the extinction that occurred at the end of the Permian, we should nevertheless bear in mind that ecosystems take a very long time to fully recover.”

Sahney and Benton looked at the recovery of tetrapods – animals with a backbone and four legs, such as amphibians and reptiles – and found that although globally tetrapods appeared to recover quickly, the dramatic restructuring that occurred at the community level was not permanent and communities did not recover numerically or ecologically until about 30 million years later.

Professor Benton explained: “Diversity is most commonly assessed by tallying the number of taxa on a global scale, but these studies are subject to the vagaries of sampling. By examining well-preserved and well-studied faunas, the taxonomic and ecological recovery of communities after the Permian extinction event can be examined more accurately, and the problems of geological bias are largely avoided.”

The Permian extinctions occurred in three waves, the largest being at the boundary between the Permian and Triassic periods, 251 million years ago. This was the most devastating ecological event of all time, thought to be caused by large-scale volcanism in Russia which produced the ‘Siberian Traps’, covering over 200,000 square kilometers (77,000 square miles) in lava.

University of Bristol

1000 Genomes Project

2008-03-07T19:01:00.002+01:00

An international research consortium today announced the 1000 Genomes Project, an ambitious effort that will involve sequencing the genomes of at least a thousand people from around the world to create the most detailed and medically useful picture to date of human genetic variation. The project will receive major support from the Wellcome Trust Sanger Institute in Hinxton, England, the Beijing Genomics Institute, Shenzhen (BGI Shenzhen) in China and the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health (NIH).

Drawing on the expertise of multidisciplinary research teams, the 1000 Genomes Project will develop a new map of the human genome that will provide a view of biomedically relevant DNA variations at a resolution unmatched by current resources. As with other major human genome reference projects, data from the 1000 Genomes Project will be made swiftly available to the worldwide scientific community through freely accessible public databases.

"The 1000 Genomes Project will examine the human genome at a level of detail that no one has done before," said Richard Durbin, Ph.D., of the Wellcome Trust Sanger Institute, who is co-chair of the consortium. "Such a project would have been unthinkable only two years ago. Today, thanks to amazing strides in sequencing technology, bioinformatics and population genomics, it is now within our grasp. So we are moving forward to build a tool that will greatly expand and further accelerate efforts to find more of the genetic factors involved in human health and disease."

Any two humans are more than 99 percent the same at the genetic level. However, it is important to understand the small fraction of genetic material that varies among people because it can help explain individual differences in susceptibility to disease, response to drugs or reaction to environmental factors. Variation in the human genome is organized into local neighborhoods called haplotypes, which are stretches of DNA usually inherited as intact blocks of information.

Recently developed catalogs of human genetic variation, such as the HapMap, have proved valuable in human genetic research. Using the HapMap and related resources, researchers already have discovered more than 100 regions of the genome containing genetic variants that are associated with risk of common human diseases such as diabetes, coronary artery disease, prostate and breast cancer, rheumatoid arthritis, inflammatory bowel disease and age-related macular degeneration.

However, because existing maps are not extremely detailed, researchers often must follow those studies with costly and time-consuming DNA sequencing to help pinpoint the precise causative variants. The new map would enable researchers to more quickly zero in on disease-related genetic variants, speeding efforts to use genetic information to develop new strategies for diagnosing, treating and preventing common diseases.

The scientific goals of the 1000 Genomes Project are to produce a catalog of variants that are present at 1 percent or greater frequency in the human population across most of the genome, and down to 0.5 percent or lower within genes. This will likely entail sequencing the genomes of at least 1,000 people. These people will be anonymous and will not have any medical information collected on them, because the project is developing a basic resource to provide information on genetic variation. The catalog that is developed will be used by researchers in many future studies of people with particular diseases.

"This new project will increase the sensitivity of disease discovery efforts across the genome five-fold and within gene regions at least 10-fold," said NHGRI Director Francis S. Collins, M.D., Ph.D. "Our existing databases do a reasonably good job of cataloging variations found in at least 10 percent of a population. By harnessing the power of new sequencing technologies and novel computational methods, we hope to give biomedical researchers a genome-wide map of variation down to the 1 percent level. This will change the way we carry out studies of genetic disease."

National Human Genome Research Institute www.genome.gov

Blue-eyed humans have a single, common ancestor

2008-02-16T14:07:00.002+01:00

New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.

“Originally, we all had brown eyes”, said Professor Eiberg from the Department of Cellular and Molecular Medicine. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch”, which literally “turned off” the ability to produce brown eyes”. The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin. The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue. The switch’s effect on OCA2 is very specific therefore. If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour – a condition known as albinism.

Limited genetic variation

Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.

Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey. His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.

Nature shuffles our genes

The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human’s chance of survival. As Professor Eiberg says, “it simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so.”

University of Copenhagen

Paleontologists say two explosive evolutionary events shaped early history of multicellular life

2008-02-12T19:55:00.000+01:00

Scientists have known for some time that most major groups of complex animals appeared in the fossils record during the Cambrian Explosion, a seemingly rapid evolutionary event that occurred 542 million years ago. Now Virginia Tech paleontologists, using rigorous analytical methods, have identified another explosive evolutionary event that occurred about 33 million years earlier among macroscopic life forms unrelated to the Cambrian animals.

They dubbed this earlier event the "Avalon Explosion."

The discovery, reported in the Jan. 4 issue of Science, suggests that more than one explosive evolutionary event may have taken place during the early evolution of animals.

The Cambrian explosion event refers to the sudden appearance of most animal groups in a geologically short time period between 542 and 520 million years ago, in the early Cambrian Period. Although there were not as many animal species as in modern oceans, most (if not all) living animal groups were represented in the Cambrian oceans.

"The explosive evolutionary pattern was a concern to Charles Darwin, because he expected that evolution happens at a slow and constant pace," said Shuhai Xiao, associate professor of geobiology at Virginia Tech. “Darwin’s perception could be represented by an inverted cone with ever expanding morphological range, but the fossil record of the Cambrian Explosion and since is better represented by a cylinder with a morphological radiation at the base and morphological constraint afterwards.”

Darwin reckoned that there should be long and hidden periods of animal evolution before the Cambrian Explosion, Xiao said.

But paleontologists have not found such evidence, and recently scientists have learned that biological evolution has not been moving on a smooth road. “Accelerated rates may characterize the early evolution of many groups of organisms,” said Michal Kowalewski, professor of geobiology at Virginia Tech.

To test whether other major branches of life also evolved in an abrupt and explosive manner, Virginia Tech graduate students Bing Shen and Lin Dong, along with Xiao and Kowalewski, analyzed the Ediacara fossils: the oldest complex, multicellular organisms that had lived in oceans from 575 to 542 million years ago; that is, before the Cambrian Explosion of animals.

"These Ediacara organisms do not have an ancestor-descendant relationship with the Cambrian animals, and most of them went extinct before the Cambrian Explosion," said Shen. “And this group of organisms – most species – seems to be distinct from the Cambrian animals.”

But how did those Ediacara organisms first evolve, Shen asked. Did they also appear in an explosive evolutionary event, or is the Cambrian Explosion a truly unparalleled event?

“We identified 50 characters and mapped the distribution of these characters in more than 200 Ediacara species. These species cover three evolutionary stages of the entire Ediacara history across 33 million years,” said Shen.

The three successive evolutionary stages are represented by the Avalon, White Sea, and Nama assemblages (all named after localities where representative fossils of each stage can be found). The earliest Avalon stage was represented by relatively few species.

Surprisingly, however, as shown by Shen and colleagues, these earliest Ediacara life forms already occupied a full morphological range of body plans that would ever be realized through the entire history of Ediacara organisms. "In other words, major types of Ediacara organisms appeared at the dawn of their history, during the Avalon Explosion," Dong said. "Subsequently, Ediacara organisms diversified in White Sea time and then declined in Nama time. But, despite this notable waxing and waning in the number of species, the morphological range of the Avalon organisms were never exceeded through the subsequent history of Ediacara."

Kowalewski said their research team had not anticipated the discovery. “Using the scientific literature, we were trying to create a more rigorous reconstruction of the morphological history of Ediacara organisms,” he said.

The process involved adapting quantitative methods that had been used previously for studying morphological evolution of animals, but never applied to the enigmatic Ediacara organisms. “We think of diversity in terms of individual species. But species may be very similar in their overall body plan. For example, 50 species of fly may not differ much from one another in terms of their overall shape – they all represent the same body plan. On the other hand, a set of just three species that include a fly, a frog and an earthworm represent much more morphological variation. We can thus think of biodiversity not only in terms of how many different species there are but also how many fundamentally distinct body plans are being represented. Our approach combined both those approaches,” said Kowalewski.

“In addition, the method relies on converting different morphologies into numerical (binary) data. This strategy allows us to describe, more objectively and more consistently, enigmatic fossil life forms, which are preserved mostly as two-dimensional impressions and are not understood well in terms of function, ecology, or physiology,” Kowalewski said.

Scientists are still unsure what were the driving forces behind the rapid morphological expansion during the Avalon explosion, and why the morphological range did not expand, shrink, or shift during the subsequent White Sea and Nama stages.

"But, one thing seems certain -- the evolution of earliest macroscopic and complex life also went through an explosive event before to the Cambrian Explosion,” Xiao said. “It now appears that at the dawn of the macroscopic life, between 575 and 520 million years ago, there was not one, but at least two major episodes of abrupt morphological expansion."

Virginia Tech

Losses of long-established genes contributed to human evolution, scientists find

2008-02-01T19:27:00.000+01:00

The evolution of new genes is not the only way for a species to change. The loss of genes may also lead to adaptations that help species survive, but this idea has not been well studied. Now, scientists at the University of California, Santa Cruz, have carried out the first systematic computational analysis to identify long-established genes that were lost during the millions of years of evolution leading to the human species. Their findings appear in the December 14 issue of PLoS Computational Biology.

"This is the first study designed to search the entire genome for recent loss of genes that do not have any near-duplicate copies elsewhere in the genome. These are likely to be the more important gene losses," said David Haussler, professor of biomolecular engineering at UCSC.

Haussler and five others in his research group--postdoctoral researcher Jingchun Zhu, graduate students Zack Sanborn and Craig Lowe, technical projects manager Mark Diekhans, and evolutionary biologist Tom Pringle--are coauthors of the paper.

"The idea that gene losses might contribute to adaptation has been kicked around, but not well studied," said Zhu, who is first author of the paper. "We found three examples in the literature, and all of them could have medical implications."

To find gene losses, Zhu employed a software program called TransMap that Diekhans had developed. The program compared the mouse and human genomes, searching for genes having changes significant enough to render them nonfunctional sometime during the 75 million years since the divergence of the mouse and the human lineages.

Genes can be lost in many ways. This study focused on losses caused by mutations that disrupt the DNA sequences known as open reading frames. These are either point mutations, where events such as the insertion or substitution of a DNA base alter the instructions encoded in the DNA, or changes that occur when a large portion of a gene is deleted altogether or moves to a new place on the genome.

Because the dog diverged from our ancient common ancestor earlier than the mouse, the researchers used the dog genome as an "out group" to filter out false positives, Sanborn said. "If a gene is still living in both dog and mouse but not in human, it was probably living in the common ancestor and then lost in the human lineage," he explained.

Using this process, they identified 26 losses of long-established genes, including 16 that were not previously known. The gene-loss candidates found in this study do not represent a complete list of gene losses in the human lineage, however, because the analysis was designed to produce more false negatives than false positives.

Next they compared the identified genes in the complete genomes of the human, chimpanzee, rhesus monkey, mouse, rat, dog, and opossum to estimate the evolutionary time when the gene was functional before it was lost. This analysis refined the timing of the gene loss and also served as a benchmark for whether the gene in question was long-established, and therefore probably functional, or merely a redundant gene copy. Through this process, they found six genes that were lost only in the human.

One previously unknown loss, the gene for acyltransferase-3 (ACYL3), particularly caught their attention. Multiple copies of the ACYL3 gene are encoded in the fly and worm genomes.

"This is an ancient protein that exists throughout the whole tree of life," said Zhu. "In the mammalian clade there is only one copy left, and somewhere along primate evolution, that copy was lost."

"In our analysis, we found that this gene contains a nonsense mutation in human and chimp, and it appears to still be functional in rhesus," added Sanborn. The researchers also found that the mutation is not present in the orangutan, so the gene is probably still functional in that species. To further narrow down the timing of the loss, the researchers looked to see if the gene is still active in the gorilla.

"On the evolutionary tree leading to human, on the branch between chimp and orangutan, sits gorilla," Sanborn explained.

After sequencing the corresponding region in a DNA sample from a gorilla, he found the gene intact, without the mutation, meaning the loss likely occurred in the primate lineage after the speciation of the gorilla and before that of the chimpanzee.

In addition to ACYL3, the researchers identified other genes that were lost in humans and did not have any "functional homologues," or alternate genes that could perform the same function, in the human genome. The researchers called these "orphan losses."

"A highlight of our research was that we were able to find a list of these orphan losses," said Zhu. "Some of them have been functional for more than 300 million years, and they were the last copies left in the human genome."

While the copies of these genes remaining in the human genome appear to be nonfunctional, functional copies of all of them exist in the mouse genome.

"These orphan genes may be interesting candidates for experimental biologists to explore," said Zhu. "It would be interesting to find out what was the biological effect of these losses. Once their function is well characterized in species that still have active copies, we could maybe speculate about their effects on human evolution."

This research was funded by the National Human Genome Research Institute, the National Institutes of Health, the National Cancer Institute, and the Howard Hughes Medical Institute.

UCSC

Lush or Lightweight?

2008-01-05T12:04:00.000+01:00

Some fruit flies can drink others under the table. Now, scientists at North Carolina State University have a few more genetic clues behind why some flies are more sensitive to alcohol than others. And the results might lead to more knowledge about alcoholism in humans.

After genetically modifying fruit flies to be either extremely sensitive or extremely resistant to alcohol – lightweights or lushes – the NC State scientists found that a number of fruit fly genes undergo changes when sensitivity to alcohol changes.

A number of these genes, the researchers report, are similar to genes found in humans, suggesting that they may be good targets to study human predisposal to alcoholism.

The research is published in the November edition of Genome Biology, which is available online at http://genomebiology.com.

The research team – Dr. Tatiana Morozova, a post-doctoral researcher in zoology; Dr. Trudy Mackay, William Neal Reynolds Professor of Genetics; and Dr. Robert Anholt, professor of zoology and genetics – used a unique approach in the study.

Rather than examining gene changes after exposure to alcohol and the development of tolerance to it, the NC State study first artificially selected flies for alcohol sensitivity – creating the lushes and the lightweights – and then, in a "whole-genome" approach, examined the entire genome, or set of all genes, to find genes that had consistent changes in expression as a response to the artificial selection.

"We wanted to find the genetic factors that changed when flies became more sensitive or more resistant to alcohol, knowing that genes that undergo changes are potential candidate genes for mediating sensitivity," Anholt said.

In the study, flies were exposed to alcohol vapors in a so-called inebriometer, a long vertical tube filled with a number of slanted platforms onto which the flies can cling. As flies became inebriated, they fell from platform to platform until they became so intoxicated that they fell to the bottom of the tube, where they were collected.

"When you expose flies to alcohol, they go through the tube at a rate more or less determined by their genetic background," Mackay said.

By mating the most extreme lightweights with other extreme lightweights for 25 generations and mating extreme lushes with other extreme lushes for 25 generations, the researchers created both "lightweight" flies that needed just a minute or two of exposure to fall to the bottom of the inebriometer and fly "lushes" that finally reached the tube's bottom after a "bender" of about 18 minutes.

More than 1,500 genes changed in testing, the study showed. Tests of 35 especially promising candidate genes showed 32 genes affecting alcohol sensitivity. Seventy-two percent of these 32 genes have human counterparts, the researchers said.

Some of these changed genes are involved in one of the metabolic pathways that converts alcohol into fat, and have not been previously studied for a correlation to alcohol sensitivity, the researchers added.

Finding relevant genes, Mackay says, could some day lead to devising a drug for people with higher genetic risk factors for alcoholism.

The study was funded by a grant from the National Institute of Alcoholism and Alcohol Abuse.

NCSU News

Strong Evidence Points to Earth’s Proximity to Sun as Ice Age Trigger

2007-10-09T19:47:00.000+02:00

Analysis of Antarctic ice cores led by Kenji Kawamura, a visiting scientist at Scripps Institution of Oceanography, UC San Diego, shows that the last four great ice age cycles began when Earth’s distance from the sun during its annual orbit became great enough to prevent summertime melts of glacial ice. The absence of those melts allowed buildups of the ice over periods of time that would become characterized as glacial periods.

Results of the study appear in the Aug. 23 edition of the journal Nature.

Jeff Severinghaus, a Scripps geoscientist and co-author of the paper, said the finding validates a theory formalized in the 1940s but first postulated in the 19th Century. The work also helps clarify the role of carbon dioxide in global warming and cooling episodes past and present, he said.

“This is a significant finding because people have been asking for 100 years the question of why are there ice ages,” Severinghaus said.

A premise advanced in the 1940s known as the Milankovitch theory, named after the Serbian geophysicist Milutin Milankovitch, proposed that ice ages start and end in connection with changes in summer insolation, or exposure to sunlight, in the high latitudes of the Northern Hemisphere. To test it, Kawamura used ice core samples taken thousands of miles to the south in Antarctica at a station known as Dome Fuji.

Scientists studying paleoclimate often use gases trapped in ice cores to reconstruct climatic conditions from hundreds of thousands of years in the past, digging thousands of meters deep into ice sheets. By measuring the ratio of oxygen and nitrogen in the cores, Kawamura’s team was able to show that the ice cores record how much sunlight fell on Antarctica in summers going back 360,000 years. The team’s method enabled the researchers to use precise astronomical calculations to compare the timing of climate change with sunshine intensity at any spot on the planet.

Kawamura, a former postdoctoral researcher at Scripps, used the oxygen-nitrogen ratio data to create a climate timeline that was used to validate the calculations Milankovitch had created decades earlier. The team found a correlation between ice age onsets and terminations, and variations in the season of Earth’s closest approach to the sun. Earth's closest pass, or perihelion, happens to fall in June about every 23,000 years. When the shape of Earth's orbit did not allow it to approach as closely to the sun in that month, the relatively cold summer on Earth encouraged the spread of ice sheets on the Northern Hemisphere's land surface. Periods in which Earth passed relatively close in Northern Hemisphere summer accelerated melt and brought an end to ice ages.

“When we start to come to the point of closest approach in June, that’s when the big ice melts off,” said Severinghaus.

Kawamura said the new timeline will serve as a guide that will allow researchers to test climate forecast models of the effects of carbon dioxide levels in the atmosphere. The team found that the changes in Earth’s orbit that terminate ice ages amplify their own effect on climate through a series of steps that leads to more carbon dioxide being released from the oceans into the air. This secondary effect, or feedback, has accounted for as much as 30 percent of the warming seen as ice ages of the past have come to an end.

“An important point is that climate models should be validated with the past climate so that we can better predict what will happen in the future with rising CO2 levels,” said Kawamura. “For that, my new timescale can distinguish the contribution to past climate change from insolation change and CO2.”

UCSD

Comet May Have Exploded Over North America 13,000 Years Ago

2007-10-01T20:21:00.000+02:00

New scientific findings suggest that a large comet may have exploded over North America 12,900 years ago, explaining riddles that scientists have wrestled with for decades, including an abrupt cooling of much of the planet and the extinction of large mammals.

The discovery was made by scientists from the University of California at Santa Barbara and their colleagues. James Kennett, a paleoceanographer at the university, said that the discovery may explain some of the highly debated geologic controversies of recent decades.

The period in question is called the Younger Dryas, an interval of abrupt cooling that lasted for about 1,000 years and occurred at the beginning of an inter-glacial warm period. Evidence for the temperature change is recorded in marine sediments and ice cores.

According to the scientists, the comet before fragmentation must have been about four kilometers across, and either exploded in the atmosphere or had fragments hit the Laurentide ice sheet in northeastern North America.

Wildfires across the continent would have resulted from the fiery impact, killing off vegetation that was the food supply of many of larger mammals like the woolly mammoths, causing them to go extinct.

Since the Clovis people of North America hunted the mammoths as a major source of their food, they too would have been affected by the impact. Their culture eventually died out.

The scientific team visited more than a dozen archaeological sites in North America, where they found high concentrations of iridium, an element that is rare on Earth and is almost exclusively associated with extraterrestrial objects such as comets and meteorites.

They also found metallic microspherules in the comet fragments; these microspherules contained nano-diamonds. The comet also carried carbon molecules called fullerenes (buckyballs), with gases trapped inside that indicated an extraterrestrial origin.

The team concluded that the impact of the comet likely destabilized a large portion of the Laurentide ice sheet, causing a high volume of freshwater to flow into the north Atlantic and Arctic Oceans.

"This, in turn, would have caused a major disruption of the ocean's circulation, leading to a cooler atmosphere and the glaciation of the Younger Dryas period," said Kennett. "We found evidence of the impact as far west as the Santa Barbara Channel Islands."

Seas could rise higher than we thought

2007-09-13T19:03:00.000+02:00

Leading climatologist Professor Stefan Rahmstorf has revealed at a UNSW public lecture that sea-level rises caused by global warming are higher than those published by the Intergovernmental Panel on Climate Change earlier this year.

Professor Rahmstorf, who is from the Potsdam Institute for Climate Impact Research, is being hosted in Sydney by UNSW’s Climate Change Research Centre, led jointly by Professor Andy Pitman and Professor Matthew England.

Professor England warned that global warming being caused by burning fossil fuels, and the resulting carbon dioxide accumulation in the atmosphere, could lead to unpredictable, non-linear effects on climate.

“The combined effects of ocean warming and melting polar ice caps will weaken the overturning of the ocean’s water, which is critical for absorbing carbon dioxide and buffering the effects of global warming,” says England, who has pioneered scientific understanding of the Southern Ocean’s relationship to climate change effects in the Southern hemisphere. “If the buffering effects of ocean overturning are greatly impeded or halted it could produce catastrophic climatic effects for the planet.”

“Sea level rise is one of the most serious long term impacts of global warming,” Professor Rahmstorf says. “The most recent information reveals that sea-levels are rising fifty per cent faster than levels predicted in the 2001 IPCC report.

“If global warming continues unabated, we could eventually see the melting of the massive ice sheets covering western Antarctica. This alone could cause global sea levels to rise by 5-7 metres and cause widespread devastation.”

The combination of higher rainfall and higher sea-level rises in the Asia-Pacific region would create millions of climate refugees. The UN estimates that some 150 million people live less than one metre above the high-tide level and 250 million live within five metres. Potential consequences of climate change include increased flooding resulting in the loss of life and property, the destruction of coastal infrastructure such as bridges and the loss of beaches and damage to wetlands.

Professor England and Professor Stefan Rahmstorf have been invited to write a new comprehensive review of the risk of abrupt ocean change for a forthcoming issue of the prestigious journal Proceedings of the National Academy of Science (PNAS).

UNSW has recently supported the establishment of the Climate Change Research Centre via its 2007 strategic initiatives fund. Priority areas of research for the centre include climate extremes, predictability, oceanic change, and terrestrial-climate interactions.

Read more here: Recent climate observations compared to projections.

A catastrophic megaflood separated Britain from France

2007-08-25T12:42:00.000+02:00

A catastrophic megaflood separated Britain from France hundreds of thousands of years ago, changing the course of British history, according to research published in the journal Nature.

The study, led by Dr Sanjeev Gupta and Dr Jenny Collier from Imperial College London, has revealed spectacular images of a huge valley tens of kilometres wide and up to 50 metres deep carved into chalk bedrock on the floor of the English Channel.

Using high-resolution sonar waves the team captured images of a perfectly preserved submerged world in the channel basin. The maps highlight deep scour marks and landforms which were created by torrents of water rushing over the exposed channel basin.

To the north of the channel basin was a lake which formed in the area now known as the southern North Sea. It was fed by the Rhine and Thames, impounded to the north by glaciers and dammed to the south by the Weald-Artois chalk ridge which spanned the Dover Straits. It is believed that a rise in the lake level eventually led to a breach in the Weald-Artois ridge, carving a massive valley along the English Channel, which was exposed during a glacial period.

At its peak, it is believed that the megaflood could have lasted several months, discharging an estimated one million cubic metres of water per second. This flow was one of the largest recorded megafloods in history and could have occurred 450,000 to 200,000 years ago.

The researchers believe the breach of the ridge, and subsequent flooding, reorganised the river drainages in north-west Europe by re-routing the combined Rhine-Thames River through the English Channel to form the Channel River.

The breach and permanent separation of the UK also affected patterns of early human occupation in Britain. Researchers speculate that the flooding induced changes in topography creating barriers to migration which led to a complete absence of humans in Britain 100,000 years ago.

Dr Sanjeev Gupta, from the Department of Earth Science & Engineering at Imperial said: “This prehistoric event rewrites the history of how the UK became an island and may explain why early human occupation of Britain came to an abrupt halt for almost 120 thousand years.”

Project collaborator, Dr Jenny Collier, also from the Department of Earth Science & Engineering, speculates on the potential for future discoveries on the continental shelves.

“The preservation of the landscape on the floor of the English Channel, which is now 30-50 m below sea-level, is far better than anyone would have expected. It opens the way to discover a host of processes that shaped the development of north-west Europe during the past million years or so,” said Dr Collier.

The Imperial research team collaborated with the UK Hydrographic Office and the Maritime Coastguard Agency (MCA) on the project. Data collected by the MCA and archived by the Hydrographic Office was originally sourced for civil safety at sea.

Scientists propose the kind of chemistry that led to life

2007-07-26T19:33:00.000+02:00

Before life emerged on earth, either a primitive kind of metabolism or an RNA-like duplicating machinery must have set the stage – so experts believe. But what preceded these pre-life steps?

A pair of UCSF scientists has developed a model explaining how simple chemical and physical processes may have laid the foundation for life. Like all useful models, theirs can be tested, and they describe how this can be done. Their model is based on simple, well-known chemical and physical laws.

The basic idea is that simple principles of chemical interactions allow for a kind of natural selection on a micro scale: enzymes can cooperate and compete with each other in simple ways, leading to arrangements that can become stable, or “locked in,” says Ken Dill, PhD, senior author of the paper and professor of pharmaceutical chemistry at UCSF.

The scientists compare this chemical process of “search, selection, and memory” to another well-studied process: different rates of neuron firing in the brain lead to new connections between neurons and ultimately to the mature wiring pattern of the brain. Similarly, social ants first search randomly, then discover food, and finally build a short-term memory for the entire colony using chemical trails.

They also compare the chemical steps to Darwin’s principles of evolution: random selection of traits in different organisms, selection of the most adaptive traits, and then the inheritance of the traits best suited to the environment (and presumably the disappearance of those with less adaptive traits).

Like these more obvious processes, the chemical interactions in the model involve competition, cooperation, innovation and a preference for consistency, they say.

The model focuses on enzymes that function as catalysts – compounds that greatly speed up a reaction without themselves being changed in the process. Catalysts are very common in living systems as well as industrial processes. Many researchers believe the first primitive catalysts on earth were nothing more complicated than the surfaces of clays or other minerals.

In its simplest form, the model shows how two catalysts in a solution, A and B, each acting to catalyze a different reaction, could end up forming what the scientists call a complex, AB. The deciding factor is the relative concentration of their desired partners. The process could go like this: Catalyst A produces a chemical that catalyst B uses. Now, since B normally seeks out this chemical, sometimes B will be attracted to A -- if its desired chemical is not otherwise available nearby. As a result, A and B will come into proximity, forming a complex.

The word “complex” is key because it shows how simple chemical interactions, with few players, and following basic chemical laws, can lead to a novel combination of molecules of greater complexity. The emergence of complexity – whether in neuronal systems, social systems, or the evolution of life, or of the entire universe -- has long been a major puzzle, particularly in efforts to determine how life emerged.

Dill calls the chemical interactions “stochastic innovation” – suggesting that it involves both random (stochastic) interactions and the emergence of novel arrangements.

“A major question about life’s origins is how chemicals, which have no self-interest, became ‘biological’ -- driven to evolve by natural selection,” he says. “This simple model shows a plausible route to this type of complexity.” Dill is also a professor of biophysics and associate dean of research in the UCSF School of Pharmacy. He is a faculty affiliate at QB3, the California Institute for Quantitative Biomedical Research, headquartered at UCSF.

Lead author of the paper is Justin Bradford, a UCSF graduate student working with Dill.

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

Evidence of the monumental strength of tyrannosaurids

2007-07-16T18:57:00.000+02:00

New evidence may help explain the brute strength of the tyrannosaurid, says a University of Alberta researcher whose research findings demonstrate how a fused nasal bone turned the animal into a "zoological superweapon."

"Fused, arch-like nasal bones are a unique feature of tyrannosaurids," said Dr. Eric Snively, a post doctoral research fellow at the U of A. "This adaptation, for instance, was keeping the T. rexes from breaking their own skull while breaking the bones of their prey."

Snively and co-authors, number-crunching physicist Donald Henderson from the Royal Tyrrell Museum of Palaeontology and Doug Phillips from the University of Calgary, compared the skulls and teeth of a number of tyrannosaurids to non-tyrannosaurids. In one of the first studies that looked at the structural mechanics of dinosaur skulls, the scientists used CT scans to investigate such factors as tooth, nasal and cranium strength. The research is published in the journal Acta Palaeontologica Polonica.

Tyrannosaurids differ from other dinosaurs in the great robustness of their teeth and skulls, enlarged areas for attachment and expansion of jaw muscles and the consequent ability to bite deeply into bone.

Snively's team found that fused tyrannosaurid nasals were stronger than unfused carnosaur nasals. This extensive fusion increased the strength of such dinosaurs as the T. rex and helped them apply powerful bites that could splinter bone. With other carnivorous dinosaurs, says Snively, skull bones might shear apart slightly when they chomped down on other animals. "With tyrannosaurs, all the bite force was delivered to the prey," he said. "The T. rex especially had a very strong skull and jaw muscles that would turn it into a zoological superweapon."

A medium-sized T. rex had even more skull strength than a larger carnivorous creature, such as the Carcharadontosaurus saharicus, with a head nearly 1-1/2 times as long.

T. rex's neck power was similarly staggering. For instance, in a split second, a T. rex could toss its head at a 45 degree angle and throw a 50-kg person five metres in the air. And that's with conservative estimates of the creature's muscle force, says Snively.

"We kept the muscle numbers down because we thought they couldn't possibly be that powerful, but Tyrrell museum colleagues showed that a T. rex's lower jaw could apply 200,000 newtons of force - that's like lifting a semi-trailer," he said. "All of the T. rex's features came together to give it the strongest bite of any land animal. The T. rex just blows everyone out of the water when it comes to strength."

University of Alberta

Cancer drug enhances long-term memory

2007-07-10T13:48:00.000+02:00

A drug used to treat cancer has been shown to enhance long-term memory and strengthen neural connections in the brain, according to a new study by UC Irvine scientists.

In the study with mice, scientists found that histone deacetylase (HDAC) inhibitors – currently used in clinical trials to attack cancerous tumors – relaxes the protein structure that organizes and compacts genomic DNA, allowing for easier activation of genes involved in memory storage. This finding suggests that HDAC inhibitors could boost memory in humans and – because of the way they work – be therapeutic for people with Alzheimer’s and Huntington’s diseases and Rubenstein-Taybi syndrome.

“We have demonstrated for the first time that HDAC inhibitors applied directly to the hippocampus enhance memory and synaptic plasticity in the brain, and we now know a molecular mechanism through which these enhancements occur,” said Marcelo Wood, assistant professor in the Department of Neurobiology and Behavior at UCI and an author of the study.

This study appears June 6 in the Journal of Neuroscience.

A protein complex called chromatin causes genomic DNA to compress much like a telephone cord shortens as it coils. When chromatin loosens, genes associated with memory can activate more easily. Previous studies have shown that the protein CBP causes chromatin to relax, thus facilitating gene activation required for memory formation. The enzymes that reverse this process, or make the chromatin tighter, are known as HDACs. UCI scientists found in this study that HDAC inhibitors loosen chromatin and lead to stronger memory formation.

“This is a fundamental aspect of molecular biology, and it is fascinating that it can impact memory, cancer and neurodegeneration – and potentially other conditions such as drug addiction and other psychiatric disorders,” said Wood, also a fellow of the UCI Center for the Neurobiology of Learning and Memory.

Wood and his colleagues placed mice in a chamber and gave them mild electric shocks, similar to static electricity shocks that humans can get when they walk across a rug and touch a doorknob. Afterward, scientists injected HDAC inhibitors into the brains of mice, targeting the hippocampus, a region involved in short-term and long-term memory. A day later, the scientists returned the mice to the chamber to see how well they remembered the place in which they received the shock. Mice treated with HDAC inhibitors froze in place significantly longer than those that did not receive the drug, indicating that the treated mice formed stronger memories of the chamber than the untreated mice. The scientists also examined brain tissue and found that neural connections in the hippocampus were stronger in the samples treated with HDAC inhibitors.

“After an event, a critical window exists when memory consolidation is occurring. During that time, genes associated with memory need to be turned on for certain types of long-term memory to be formed,” Wood said. “For the HDAC inhibitor to enhance memory, we need to administer the drug during this critical period when gene expression is required.”

The protein CBP must be present for HDAC inhibitors to improve memory, Wood and his colleagues discovered. Tested in mice genetically engineered without CBP, the HDAC inhibitors did not improve memory. When CBP is blocked in humans, it can lead to neurodegeneration associated with Huntington’s disease and cognitive deficits in Rubenstein-Taybi syndrome. HDAC inhibitors may help overcome that blockage and lead to better neural function in people with those disorders – and perhaps improve memory as well.

UCI scientist Sara Cabrera, and researchers from the University of Pennsylvania, Oregon Health and Science University, and St. Jude Children’s Research Hospital worked on this study.

University of California, Irvine

Report Offers Guidance on How to Safely Explore Vast Aquatic Systems Buried Under Antarctic Ice

2007-07-04T12:49:00.000+02:00

The National Science Foundation (NSF) should work within the environmental framework of the international Antarctic Treaty system to develop a global scientific consensus on minimally disruptive ways to investigate one of the "last unexplored places on Earth"--a unique system of lakes, and the aquatic systems that may connect them, buried thousands of meters under the Antarctic ice sheet--according to a newly released report.

To avoid contaminating these lakes and other features, which scientists have only recently discovered and which have been cut off from the outside world for millions of years, the report calls for NSF to work with international scientific organizations and Treaty signatories to develop a management plan for any potential exploration efforts and, as part of that plan, "ensure that the environmental management of subglacial environments is held to the highest standards."

The report, "Exploration of Antarctic Subglacial Aquatic Environments: Environmental and Scientific Stewardship," was released in early May by the National Research Council of the National Academies of Science.

But before any efforts are made to take any samples, the report stresses, much more detailed surveys need to be made to catalogue the subglacial aquatic network and allow it to be afforded Treaty protection. Such a survey, while enabling the protecting of the entire system, would also allow for designating certain features more useful for scientific research and presenting less of a risk of widespread contamination of a subglacial "watershed."

The Department of State coordinates U.S. policy on Antarctica, working closely with NSF, which administers and manages the U.S. Antarctic Program. The State Department leads the U.S. delegation to the annual Antarctic Treaty Consultative Meeting (ATCM). NSF leads the ACTM's Committee on Environmental Protection.

NSF had requested guidance from the Academies on developing a set of environmental and scientific standards to guide scientifically responsible exploration. The report is the result of that request.

A subgroup of the Scientific Committee on Antarctic Research, called the Subglacial Antarctic Lake Environments (SALE) group, is scheduled to meet June 6 and 7 in Big Sky, Montana. John Priscu, a researcher at Montana State University, is organizing the meeting. A discussion of the report and its findings will be among the items on the agenda.

Ice-penetrating radar and other studies have identified more than 145 subglacial lakes under the ice of the southernmost continent, including one under the South Pole itself. The largest known is Lake Vostok, which has a surface area of roughly 14,000 square kilometers (5,400 square miles), making it roughly the size of Lake Ontario in North America.

Other studies have revealed that shallow, swamp-like features the size of several city blocks and layers of soils and broken rock may exist beneath the ice, adding to the diversity of subglacial aquatic environments. Scientific evidence further indicates that these environments comprise vast watersheds some of which appear to be connected by rivers and streams that flow freely beneath the ice sheet, which in most places is more than two miles thick.

"These lakes and their connected systems are among the last unexplored places on Earth," the report says. "Moreover, they have been sealed from free exchange with the atmosphere for millions of years, making it possible for unique microbial communities to exist."

In addition to the opportunity to study potentially unique microorganisms that have evolved in isolation for millions of years in extremes of cold and darkness, scientists are interested in these environments because sediments at the bottom of the lakes may contain evidence of past climate on the continent over millions of years and possibly even of a time before Antarctica was covered by ice.

This previously unknown system of aquatic features appears to be interconnected in many ways, the report notes, requiring that great care be taken in choosing which features to eventually explore in order to prevent accidentally contaminating an entire watershed.

But the 12-member expert panel that drafted the recommendations also recognized that in order to fully understand these unique environments it will eventually be necessary to sample the waters, most likely by drilling through the ice sheet to obtain the samples or introduce instruments.

"Direct exploration of subglacial environments is required if we are to understand these unique systems," the report states. "Exploration...should proceed and take a conservative approach to stewardship and management while encouraging field research."

Although previous drilling at Lake Vostok has reached to 120 meters above the place where ice and lake water meet, none of the Antarctic lakes has yet been breached. But plans are being actively pursued to explore more than one of Antarctica's lakes, with Russia having stated its intention to drill into Lake Vostok during the 2007-2008 Antarctic research season, which begins in the fall.

NSF supported scientists have studied various biological and geophysical aspects of Lake Vostok for several years.

Under its program of grants for the International Polar Year 2007-2008 (IPY), NSF has funded genomic studies of microbes found in Lake Vostok, not from the waters themselves, but from the ice that melted and refrozen at the interface of the ice sheet above and lake waters below. Another IPY grant will support an airborne imaging system to map the lake. The White House Office of Science and Technology Policy has designated NSF as the lead U.S. agency for IPY.

In the Academies' report, the panel recommends that before any of the aquatic systems are penetrated that comprehensive surveys should be made to insure that scientists have identified and catalogued all of the existing subglacial lakes and drainage systems to understand how the complex system is connected and to identify the best potential research sites.

Once the features are identified and catalogued, they should then designated as specially protected areas under the Treaty to ensure that scientific activities can be managed within an international plan. Some of the features, it adds, should be designated as "exemplar pristine" environments and afforded additional environmental protection.

The panel recognizes that, as is typically the case with spacecraft that visit other planets, it is likely impossible to insure that physically entering the lake with drills and other probes will not introduce contaminants. It therefore recommends that any effort to physically explore the lake be restricted to introducing concentrations of microbes that are less than those that naturally occur as microscopic life transported from other parts of the globe travel down through the ice sheet and into the waters below.

Even so, the report recommends that "investigators should make every effort practicable to maintain the integrity of lake chemical and physical structure during exploration."

Vigorous Exercise Keeps People Thin with Age

2007-06-14T18:51:00.000+02:00

The old adage “use it or lose it” is truer than ever. People who maintain a vigorously active lifestyle as they age gain less weight than people who exercise at more moderate levels, according to a first-of-its-kind study that tracked a large group of runners who kept the same exercise regimen as they grew older.

The study also found that maintaining exercise with age is particularly effective in preventing extreme weight gain, which is associated with high blood pressure, high cholesterol, diabetes, and other diseases.

The study, conducted by Paul Williams of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), followed 6,119 men and 2,221 women who maintained their weekly running mileage (to within three miles per week) over a seven-year period. On average, the men and women who ran over 30 miles per week gained half the weight of those who ran less than 15 miles per week.

“To my knowledge, this is the only study of its type,” says Williams, a staff scientist in Berkeley Lab’s Life Sciences Division. “Other studies have tracked exercise over time, but the majority of people will have changed their exercise habits considerably.”

The research is the latest report from the National Runners' Health Study, a 20-year research initiative started by Williams that includes more than 120,000 runners. It appears in the May 3 issue of the journal Medicine and Science in Sports and Exercise.

Specifically, between the time subjects entered the study and when they were re-contacted seven years later, 25-to-34-year-old men gained 1.4 pounds annually if they ran less than 15 miles per week. In addition, male runners gained 0.8 pounds annually if they ran between 15 and 30 miles per week, and 0.6 pounds annually if they ran more than 30 miles per week.

This trend is mirrored in women. Women between the ages of 18 and 25 gained about two pounds annually if they ran less than 15 miles per week, 1.4 pounds annually if they ran 15 to 30 miles per week, and slightly more than three-quarters of a pound annually if they ran more than 30 miles per week. Other benefits to running more miles each week included fewer inches gained around the waist in both men and women, and fewer added inches to the hips in women.

“As these runners aged, the benefits of exercise were not in the changes they saw in their bodies, but how they didn’t change like the people around them,” says Williams.

Although growing older and gaining weight is something of a package deal, it isn’t the same in everyone. The lucky few remain lean as they age, most people pack on several pounds, and some people become obese. The latter group is particularly at risk for high blood pressure, high cholesterol, and diabetes. Fortunately, Williams’ results show that maintaining exercise can combat such extreme weight gain.

“Getting people to commit to a vigorously active lifestyle while young and lean will go a long way to reducing the obesity epidemic in this country,” says Williams.

Another paper published in the November 2006 issue of the journal Obesity by Williams and Paul Thompson of Hartford (CT) Hospital found that runners who increased their running mileage gained less weight than those who remained sedentary, and runners that quit running became fatter.

“The time to think about exercise is before you think you need it,” says Williams. “The medical journals are full of reports on how difficult it is to regain the slenderness of youth. The trick is not to get fat.”

Williams’ research was funded by the National Heart, Lung and Blood Institute. The May 3 paper in the journal Medicine and Science in Sports and Exercise is entitled Maintaining Vigorous Activity Attenuates 7-yr Weight Gain in 8,340 Runners.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

Visit our Website at www.lbl.gov

New Deep-Sea Hydrothermal Vents, Life Form Discovered

2007-05-22T20:32:00.000+02:00

A new "black smoker"--an undersea mineral chimney emitting hot springs of iron-darkened water--has been discovered at 8,500-foot depths by an expedition funded by the National Science Foundation (NSF) to explore the Pacific Ocean floor off Costa Rica.

Scientists from Duke University, the Universities of New Hampshire and South Carolina, and the Woods Hole Oceanographic Institution in Massachusetts have named their discovery the Medusa Hydrothermal Vent Field.

The researchers chose that name to highlight the presence there of a unique pink form of the jellyfish order stauromedusae. The jellyfish resemble "the serpent-haired Medusa of Greek myth," said expedition leader Emily Klein, a geologist at Duke University.

The bell-shaped jellyfish sighted near the vents may be of a new species "because no one has seen this color before," said Karen Von Damm, a geologist at the University of New Hampshire.

According to Von Damm, stauromedusae are usually found away from high-temperature hydrothermal vents, where the fluids are a little bit cooler, not close to the vents as these are.

Aboard the Research Vessel (R/V) Atlantis, the researchers are studying ocean floor geology of the East Pacific Rise, one of the mid-ocean ridge systems where new crust is made as the earth spreads apart to release molten lava.

"Each new vent site has the potential to reveal new discoveries in interactions between hot rocks beneath the seafloor, the fluids that interact with those rocks and the oceans above, as well as a rich biosphere that depends on vent processes," said Adam Schultz, program director in NSF's Division of Ocean Sciences, which funded the expedition through its Ridge 2000 program. "This discovery has implications for understanding the origin of Earth's crust, its evolution over time and how living organisms adapt to extreme environmental conditions."

Jason II, a remotely-controlled robotic vehicle the scientists are using to probe the vent field, logged water temperatures of 330 degrees Celsius (626 degrees Fahrenheit) at the mouth of one of the vents. Jason II subsequently found a second vent about 100 yards away.

Von Damm said that heat-tolerant tubeworms found living on Medusa's chimneys, a type known as alvinellids, are commonplace in the equatorial Pacific and thrive on high-iron fluids. Jason also has retrieved two other types of tubeworms--tevnia and riftia--from the vent area.

In addition, the camera-studded robot, which can collect biological specimens with the aid of the mechanical arms it uses to remove rock samples, has gathered samples of mussels from the vent area.

According to Von Damm, wherever there are mid-ocean ridges, scientists frequently find geothermal vents warmed by heat energy from underlying volcanic conduits.

"Each new vent sparks fresh excitement, because each one is different. Every vent has a different chemistry, and that helps us understand the processes going on in the ocean crust. Each one gives us a different piece of the puzzle," Von Damm said.

More than 500 new species have been found at vents since they were first discovered in 1977.

"After looking at relatively barren lava flows for several days on this expedition," said geologist Scott White of the University of South Carolina, "we all knew it would be special when we found creatures living at this new vent field."

National Science Foundation (NSF)

When fish first started biting

2007-05-19T19:50:00.000+02:00

Before fish began to invade land, about 365 million years ago, they had some big problems to solve. They needed to come up with new ways to move, breathe, and eat.

Take the latter, for example. Fish usually pucker up and suck prey into their mouths. But air is 900 times less dense than water, so land-livers must bite into their food to get a meal. Researchers at Harvard University have just completed a study that gives a clear picture of how that change was made.

“Aquatic creatures developed the tools they needed to feed on land before they completely left water,” notes Molly Markey, a lecturer on earth and planetary sciences. “Our research suggests that these first tetrapods, four-footed animals, bit on prey in shallow water or on land. Although they may have occasionally captured a meal by suction.”

To become biters, the invaders had to change their teeth and skulls, and learn to walk. Along with Charles Marshall, a professor of biology and of geology at Harvard’s Museum of Comparative Zoology, Markey compared the boney remains of a 365-million-year-old fish named Eusthenopteron, two ancient tetrapods called Acanthostega and Phonerpeton, and a modern fish. The salamanderlike Acanthostega spent much of its life in the water, Phonerpeton lived on land. Both Acanthostega and Eusthenopteron possessed lungs and gills, so they could breathe air or water, like today’s lungfishes. All three ancients boasted pointed teeth, indicating that they were meat-eating predators.

Studies done by Jenny Clark at Cambridge University in England show that Acanthostega had short legs that stuck out to its sides, ending in what look like webbed toes. Such limbs would not be very supportive, so it’s likely that the old tetrapod slithered or scooted, rather than walked, when it ventured on land.

One big question is why Acanthrostega and its relatives left their aquatic domain in the first place. Were they trying to get away from bigger predators, or were they looking for new prey to feed on? “It’s likely that both reasons are true,” Markey says.

Markey and Marshall compared models of the ancient tetrapods and Eusthenopteron, the fish that stayed at home. They published their findings in the April 16 online edition of the Proceedings of the National Academy of Sciences.

The comparison found that the key to evolving from sucking to biting lay in the tops of the animals’ skulls. These boney skull roofs, rather than being solid, were made up of lots of different pieces. Markey compares them to pieces of a jigsaw puzzle. “Imagine that skull bones are puzzle pieces,” she explains. “Places where they touch each other are known as sutures, and the bones can move around them a bit. The sutures get wider or narrower depending on motions such as chewing.”

By analyzing sutures in the skulls of the ancient tetrapods and fish, then comparing them with those in a living fish, the researchers could determine how the skull roof deformed under the compression and tension of eating. Such analyses led to the conclusion that Eusthenopteron was a sucker and the awkward-moving Acanthostega was a biter — perhaps the first one in the animal kingdom.

Harvard News Office

Dinosaur extinction didn’t cause the rise of present-day mammals

2007-05-16T20:24:00.000+02:00

A new, complete 'tree of life' tracing the history of all 4,500 mammals on Earth shows that they did not diversify as a result of the death of the dinosaurs, says new research published in Nature today.

The study was undertaken in the UK by scientists at Imperial College London and the Zoological Society of London (ZSL). It contradicts the previously accepted theory that the Mass Extinction Event (MEE) that wiped out the dinosaurs 65 million years ago prompted the rapid rise of the mammals we see on the earth today.

The multinational research team has been working for over a decade to compile the tree of life from existing fossil records and new molecular analyses. They show that many of the genetic 'ancestors' of the mammals we see around us today existed 85 million years ago, and survived the meteor impact that is thought to have killed the dinosaurs. However, throughout the Cretaceous epoch, when dinosaurs walked the earth, these mammal species were relatively few in number, and were prevented from diversifying and evolving in ecosystems dominated by dinosaurs.

The tree of life shows that after the MEE, certain mammals did experience a rapid period of diversification and evolution. However, most of these groups have since either died out completely, such as Andrewsarchus (an aggressive wolf-like cow), or declined in diversity, such as the group containing sloths and armadillos.

The researchers believe that our 'ancestors', and those of all other mammals on earth now, began to radiate around the time of a sudden increase in the temperature of the planet – ten million years after the death of the dinosaurs.

Professor Andy Purvis from Imperial College London's Division of Biology explains: "Our research has shown that for the first 10 or 15 million years after the dinosaurs were wiped out, present day mammals kept a very low profile, while these other types of mammals were running the show. It looks like a later bout of 'global warming' may have kick-started today’s diversity – not the death of the dinosaurs.

"This discovery rewrites our understanding of how we came to evolve on this planet, and the study as a whole gives a much clearer picture than ever before as to our place in nature."

Dr Kate Jones from the Zoological Society of London adds: "Not only does this research show that the extinction of the dinosaurs did not cause the evolution of modern-day mammals, it also provides us with a wealth of other information. Vitally, scientists will be able to use the research to look into the future and identify species that will be at risk of extinction. The benefit to global conservation will be incalculable."

The study was supported by the UK Natural Environment Research Council (NERC), the National Center for Ecological Analysis and Synthesis (NCEAS), the German Federal Ministry of Education and Research (BMBF), the German Research Association (DFG) Heisenberg, the Leverhulme Trust, the National Science Foundation (NSF), the Earth Institute at Columbia University, and the Cyberinfrastructure for Phylogenetic Research (CIPRES).

Imperial College London

Engineers create 'optical cloaking' design for invisibility

2007-05-14T20:01:00.000+02:00

Researchers using nanotechnology have taken a step toward creating an "optical cloaking" device that could render objects invisible by guiding light around anything placed inside this "cloak."

The Purdue University engineers, following mathematical guidelines devised in 2006 by physicists in the United Kingdom, have created a theoretical design that uses an array of tiny needles radiating outward from a central spoke. The design, which resembles a round hairbrush, would bend light around the object being cloaked. Background objects would be visible but not the object surrounded by the cylindrical array of nano-needles, said Vladimir Shalaev, Purdue's Robert and Anne Burnett Professor of Electrical and Computer Engineering.

The design does, however, have a major limitation: It works only for any single wavelength, and not for the entire frequency range of the visible spectrum, Shalaev said.

"But this is a first design step toward creating an optical cloaking device that might work for all wavelengths of visible light," he said.

Research findings are detailed in a paper appearing this month in the journal Nature Photonics. The paper, which is appearing online this week, was co-authored by doctoral students Wenshan Cai and Uday K. Chettiar, research scientist Alexander V. Kildishev and Shalaev, all in Purdue's School of Electrical and Computer Engineering.

Calculations indicate the device would make an object invisible in a wavelength of 632.8 nanometers, which corresponds to the color red. The same design, however, could be used to create a cloak for any other single wavelength in the visible spectrum, Shalaev said.

"How to create a design that works for all colors of visible light at the same time will be a big technical challenge, but we believe it's possible," he said. "It is clearly doable. In principle, this cloak could be arbitrarily large, as large as a person or an aircraft."

The research is based at the Birck Nanotechnology Center at Purdue's Discovery Park.

Other researchers published findings in 2006 describing the mathematics generally required for the optical cloaking device. Those researchers include: John Pendry at the Imperial College in London, along with David Schurig and David R. Smith at Duke University, and simultaneously, Ulf Leonhardt at the University of St. Andrews in Scotland.

"These mathematical requirements were very general, and then we determined how to fulfill the requirements with a specific design," Shalaev said.

Leonhardt, a professor of theoretical physics, wrote a commentary piece about the Purdue paper appearing in the same issue of Nature Photonics. In the commentary, he compares the Purdue design to the Roman creation of "the first optical metamaterial," a type of glass containing nanometer-scale particles of gold. In ordinary daylight, a cup made of the glass appeared green, but then it glowed ruby when illuminated from the inside.

The Purdue research, Leonhardt writes, represents " ... theoretical simulations that show that a modified Roman cup based on modern nanofabrication technology will act as an invisibility device ... Any object you put inside will disappear as if dissolved in air, provided it is viewed through polarizing tinted glasses of precisely that colour."

Other researchers have developed concepts for cloaking objects smaller than the wavelengths of visible light and for objects detected in the microwave range of the spectrum, which are much larger than the wavelengths of visible light. But the new design is the first for cloaking an arbitrary object in the range of light visible to humans.

"What we propose is the cloaking of objects of any shape and size," Shalaev said.

Two requirements are needed to render an object invisible: Light must not reflect off of the object, and the light must bend around the object so that people would see only the background and not the cloaked object itself.

"If you satisfied only the first requirement of preventing light from reflecting off of the object, you would still see the dark shadowlike shape of the object, so you would know something was there," Shalaev said. "The most difficult requirement is to bend light around the cloaked object so that the background is visible but not the object being cloaked. The viewer would, in effect, be seeing around, or through, the object."

The device would be made of so-called "non-magnetic metamaterials." Meta in Greek means beyond, so the term metamaterial means to create something that doesn't exist in nature. Unlike designs for invisibility in the microwave range, the new design has no magnetic properties. Having no magnetic properties makes it much easier to cloak objects in the visible range but also causes a small amount of light to reflect off of the cloaked object.

"But this could, in principle, be offset by other means, for example, with antireflective coatings," Shalaev said. "The big challenge is how to make rays bend around the object, which we have described how to do in this paper."

A key factor in the design is the ability to reduce the "index of refraction" to less than 1. Refraction occurs as electromagnetic waves, including light, bend when passing from one material into another. Refraction causes the bent-stick-in-water effect, which occurs when a stick placed in a glass of water appears bent when viewed from the outside. Each material has its own refraction index, which describes how much light will bend in that particular material and defines how much the speed of light slows down while passing through a material.

Natural materials typically have refractive indices greater than 1. The new design reduces a refractive index to values gradually varying from zero at the inner surface of the cloak, to 1 at the outer surface of the cloak, which is required to guide light around the cloaked object.

Creating the tiny needles would require the same sort of equipment already used to fabricate nanotech devices. The needles in the theoretical design are about as wide as 10 nanometers, or billionths of a meter, and as long as hundreds of nanometers. They would be arranged in layers emanating from a central spoke in a cylindrical shape. A single nanometer is roughly the size of 20 hydrogen atoms strung together.

Although the design would work only for one frequency, it still might have applications, such as producing a cloaking system to make soldiers invisible to night-vision goggles.

"Because night-imaging systems detect only a specific wavelength, you could, in theory, design something that cloaks in that narrow band of light," Shalaev said.

Another possible application is to cloak objects from "laser designators" used by the military to illuminate a target, he said.

Leonhardt says in his commentary that creating a cloak for rendering total invisibility in the entire visible spectrum would require "further advances in optical metamaterials, new combinations of nanotechnology with highly abstract ideas ..."

The optical cloaking research is an indirect spinoff of research in Shalaev's lab that has been funded by the U.S. Army Research Office to develop metamaterials. In previous work, Shalaev's team created a metamaterial that has a "negative index of refraction" in the wavelength of light used for telecommunications, a step that could lead to better communications and imaging technologies. More recently, the researchers moved the wavelength for a negative refractive index material to the visible range.

Purdue University

"Missing Mass" Found in Recycled Dwarf Galaxies

2007-05-13T20:59:00.000+02:00

Astronomers studying dwarf galaxies formed from the debris of a collision of larger galaxies found the dwarfs much more massive than expected, and think the additional material is "missing mass" that theorists said should not be present in this kind of dwarf galaxy.

The scientists used the National Science Foundation's Very Large Array (VLA) radio telescope to study a galaxy called NGC 5291, 200 million light-years from Earth. This galaxy collided with another 360 million years ago, and the collision shot streams of gas and stars outward. Later, the dwarf galaxies formed from the ejected debris.

"Our detailed studies of three 'recycled' dwarf galaxies in this system showed that the dwarfs have twice as much unseen matter as visible matter. This was surprising, because they were expected to have very little unseen matter," said Frederic Bournaud, of the French astrophysics laboratory AIM of the French CEA and CNRS. Bournaud and his colleagues announced their discovery in the May 10 online issue of the journal Science.

"Dark matter," which astronomers can detect only by its gravitational effects, comes, they believe, in two basic forms. One form is the familiar kind of matter seen in stars, planets, and humans -- called baryonic matter -- that does not emit much light or other type of radiation. The other form, called non-baryonic dark matter, comprises nearly a third of the Universe but its nature is unknown.

The visible portion of spiral galaxies, like our own Milky Way, lies mostly in a flattened disk, usually with a bulge in the center. This visible portion, however, is surrounded by a much larger halo of dark matter. When spiral galaxies collide, the material expelled outward by the interaction comes from the galaxies' disks. For this reason, astronomers did not expect that "recycled" dwarf galaxies formed from this collision debris would contain much, if any, dark matter.

When Bournaud and his international team of scientists used the VLA to study three dwarf galaxies formed from the debris of NGC 5291's collision, they were surprised to find two to three times the amount of dark matter as visible matter in the dwarfs. They determined the dwarfs' masses by measuring the Doppler shift of radio waves emitted by atomic Hydrogen at a frequency of 1420 MHz. The amount of shift in the frequency indicated the rotational speed in the galaxy. That, in turn, allowed the scientists to calculate the dwarf's mass.

Images from two NASA satellites provided vital information about the dwarf galaxies. "Using ultraviolet images from the Galex satellite and infrared data collected by the Spitzer satellite, we had previously shown that the dwarfs all along the debris stream were star-forming galaxies," said Pierre-Alain Duc, also of the AIM laboratory (CEA/CNRS).

What is the dark matter in the dwarfs? The astronomers don't believe it is the mysterious non-baryonic type, but rather cold Hydrogen molecules that are extremely difficult to detect.

When the astronomers performed computer models of the collision of NGC 5291 to simulate the formation of the system seen today, the models left the resulting recycled dwarfs with almost no dark matter. These computer models had started off with all the dark matter in the galaxy's larger halo.

"The result of the computer models means that the additional mass we see in the real dwarfs came from the disks, not the haloes, of the larger galaxies that collided," Bournaud said. That additional mass, the scientists believe, almost certainly is "normal" baryonic matter, probably cold molecular Hydrogen.

While the discovery about NGC 5291's neighboring dwarf galaxies sheds new light on the composition of spiral galaxies, it doesn't tell the scientists anything about the non-baryonic dark matter, whose nature remains a mystery. "Still, this new information about the matter comprising galactic disks should help us work toward a better understanding of their formation and evolution," Bournaud concluded.

Bournaud and Duc worked with Mederic Boquien, also of the AIM laboratory (CEA/CNRS); Elias Brinks of the University of Hertfordshire in the UK; Phillipe Amram of the Astronomical Observatory of Marseille-Provence; Ute Lisenfeld of the University of Granada, Spain; Barbel S. Koribalski of the Australia Telescope National Facility; Fabian Walter of the Max Planck Institute for Astronomy in Heidelberg, Germany; and Vassilis Charmandaris of the University of Crete, Greece.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The California Institute of Technology leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, a division of Caltech, manages the mission and built the science instrument, and also manages the Spitzer Space Telescope

National Radio Astronomy Observatory

How Does the Brain Tell Time?

2007-05-12T19:07:00.000+02:00

"Time" is the most popular noun in the English language, yet how would we tell time if we didn't have access to the plethora of watches, clocks and cell phones at our disposal? For decades, scientists have believed that the brain possesses an internal clock that allows it to keep track of time. Now, a UCLA study of the journal Neuron proposes a new model in which a series of physical changes to the brain's cells helps the organ to monitor the passage of time.

"The value of this research lies in understanding how the brain works," said Dean Buonomano, associate professor of neurobiology and psychiatry at the David Geffen School of Medicine at UCLA and a member of the university's Brain Research Institute. "Many complex human behaviors — from understanding speech to playing catch to performing music — rely on the brain's ability to accurately tell time. Yet no one knows how the brain does it."

The most popular theory assumes that a clock-like mechanism — which generates and counts regular fixed movements — underlies timing in the brain. In contrast, Buonomano suggests a physical model that operates without using a clock. He offered an analogy to explain how it works.

"If you toss a pebble into a lake," Buonomano said, "the ripples of water produced by the pebble's impact act like a signature of the pebble's entry time. The farther the ripples travel, the more time has passed.

"We propose that a similar process takes place in the brain that allows it to track time," he said. "Every time the brain processes a sensory event, such as a sound or flash of light, it triggers a cascade of reactions between brain cells and their connections. Each reaction leaves a signature that enables the brain cell network to encode time."

The UCLA team used a computer model to test this theory. By simulating a network of interconnected brain cells in which each connection changed over time in response to stimuli, they were able to show that the network could tell time.

Their simulations indicated that a specific event is encoded within the context of events that precede it. In other words, if one could measure the response of many neurons in the brain to a tone or a flash of light, the response would reveal not only the nature of the event but the other events that preceded it and when they occurred.

The UCLA team tested the model by asking research volunteers in the study to judge the interval between two auditory tones under a variety of different conditions. The researchers found that volunteers' sense of timing was impaired when the interval was randomly preceded by a "distracter" tone.

"Our results suggest that the timing mechanisms that underlie our ability to recognize speech and enjoy music are distributed throughout the brain and do not resemble the conventional clocks we wear on our wrists," Buonomano said.

Because time-related information is critical to understanding speech, determining how the brain tells time represents an important step toward understanding the causes of diseases, such as dyslexia, that result in impaired linguistic abilities, he said.

The next step for the research will be recording the response from a large number of brain cells to determine whether they encode information about the timing of stimuli.

Buonomano collaborated with Uma Karmarkar, now a postdoctoral fellow at the University of California, Berkeley. The National Institute of Mental Health funded the study.

UCLA

James Webb Space Telescope

2007-05-12T13:05:00.000+02:00

The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope, scheduled for launch in 2013. JWST will find the first galaxies that formed in the early Universe, connecting the Big Bang to our own Milky Way Galaxy. JWST will peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System. JWST's instruments will be designed to work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range.

JWST will have a large mirror, 6.5 meters (21.3 feet) in diameter and a sunshield the size of a tennis court. Both the mirror and sunshade won't fit onto the rocket fully open, so both will fold up and open only once JWST is in outer space. JWST will reside in an orbit about 1.5 million km (1 million miles) from the Earth.

This May, there will be more than one "web slinger" coming to town. In addition to the superhero, who will make his third movie appearance, NASA has its own "Webb" slinger – the James Webb Space Telescope. The Webb space telescope will be much larger than the Hubble Space Telescope, its predecessor. A life-sized model of the "Webb" telescope is coming to the National Mall, Washington.

NASA and Northrop Grumman, the contractor who built the model, will set up information booths next to the model, where visitors can get information and educational materials, and speak with people who are involved in the project to build the real James Webb Space Telescope.

The full-scale telescope model was built to give the viewing public a better understanding of the size, scale and complexity of this breakthrough satellite. Specifically designed for an environment subject to gravity and weather, the model is constructed mainly of aluminum and steel, weighs 12,000 lbs., and is approximately 80 feet long, 40 feet wide and 40 feet tall. A specially manufactured material imported from France called "Ferrari Precontraint" allows the sunshield to 'breathe.' The model requires 2 trucks for shipping, and assembly takes a crew of 12 approximately four days.

Image/animation above: This animation shows the JWST Sunshield unfolding like a spiderweb, as it will appear after its launch into space. Click image to view animation. Credit: Animation courtesy of Northrop Grumman Space Technology

James Webb Space Telescope

NASA Finds Extremely Hot Planet, Makes First Exoplanet Weather Map

2007-05-11T18:42:00.000+02:00

Researchers using NASA's Spitzer Space Telescope have learned what the weather is like on two distant, exotic worlds. One team of astronomers used the infrared telescope to map temperature variations over the surface of a giant gas planet, HD 189733b, revealing it likely is whipped by roaring winds. Another team determined that the gas planet HD 149026b is the hottest yet discovered.

"We have mapped the temperature variations across the entire surface of a planet that is so far away, its light takes 60 years to reach us," said Heather Knutson of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of the paper describing HD 189733b.

The two planets are "hot Jupiters" -- sizzling, gas giant planets that zip closely around their stars. Roughly 50 of the more than 200 known planets outside our solar system, called exoplanets, are hot Jupiters. Visible-light telescopes can detect these strange worlds and determine certain characteristics, such as their sizes and orbits, but not much is known about their atmospheres or what they look like.

Since 2005, Spitzer has been revolutionizing the study of exoplanets' atmospheres by examining their infrared light, or heat. In one of the new studies, Spitzer set its infrared eyes on HD 189733b, located 60 light-years away in the constellation Vulpecula. HD 189733b is the closest known transiting planet, which means that it crosses in front and behind its star when viewed from Earth. It races around its star every 2.2 days.

Spitzer measured the infrared light coming from the planet as it circled around its star, revealing its different faces. These infrared measurements, comprising about a quarter of a million data points, were then assembled into pole-to-pole strips, and, ultimately, used to map the temperature of the entire surface of the cloudy, giant planet.

The observations reveal that temperatures on this balmy world are fairly even, ranging from 650 degrees Celsius (1,200 Fahrenheit) on the dark side to 930 degrees Celsius (1,700 Fahrenheit) on the sunlit side. HD 189733b, and all other hot Jupiters, are believed to be tidally locked like our moon, so one side of the planet always faces the star. Since the planet's overall temperature variation is mild, scientists believe winds must be spreading the heat from its permanently sunlit side around to its dark side. Such winds might rage across the surface at up to 9600 kilometers per hour (6,000 miles per hour). The jet streams on Earth travel at 322 kilometers per hour (200 miles per hour).

"These hot Jupiter exoplanets are blasted by 20,000 times more energy per second than Jupiter," said co-author David Charbonneau, also of the Harvard-Smithsonian Center for Astrophysics. "Now we can see how these planets deal with all that energy."

Also, HD 189733b has a warm spot 30 degrees east of "high noon," or the point directly below the star. In other words, if the high-noon point were in Seattle, the warm spot would be in Chicago. Assuming the planet is tidally locked to its parent star, this implies that fierce winds are blowing eastward.

In the second Spitzer study, astronomers led by Joseph Harrington of the University of Central Florida in Orlando discovered that HD 149026b is a scorching 2,038 degrees Celsius (3,700 Fahrenheit), even hotter than some low-mass stars. Spitzer was able to calculate the temperature of this transiting planet by observing the drop in infrared light that occurs as it dips behind its star.

"This planet is like a chunk of hot coal in space," said Harrington. "Because this planet is so hot, we believe its heat is not being spread around. The day side is very hot, and the night side is probably much colder."

HD 149026b is located 256 light-years away in the constellation Hercules. It is the smallest and densest known transiting planet, with a size similar to Saturn's and a core suspected to be 70 to 90 times the mass of Earth. It speeds around its star every 2.9 days.

According to Harrington and his team, the oddball planet probably reflects almost no starlight, instead absorbing all of the heat into its fiery body. That means HD 149026b might be the blackest planet known, in addition to the hottest.

Spitzer Space Telescope

Nanogenerator Provides Continuous Electrical Power

2007-05-10T23:27:00.000+02:00

Researchers have demonstrated a prototype nanometer-scale generator that produces continuous direct-current electricity by harvesting mechanical energy from such environmental sources as ultrasonic waves, mechanical vibration or blood flow.

Based on arrays of vertically-aligned zinc oxide nanowires that move inside a novel “zig-zag” plate electrode, the nanogenerators could provide a new way to power nanoscale devices without batteries or other external power sources.

“This is a major step toward a portable, adaptable and cost-effective technology for powering nanoscale devices,” said Zhong Lin Wang, Regents’ Professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “There has been a lot of interest in making nanodevices, but we have tended not to think about how to power them. Our nanogenerator allows us to harvest or recycle energy from many sources to power these devices.”

Details of the nanogenerator are reported in the April 6 issue of the journal Science. The research was sponsored by the Defense Advanced Research Projects Agency (DARPA), the National Science Foundation (NSF), and the Emory-Georgia Tech Center of Cancer Nanotechnology Excellence.

The nanogenerators take advantage of the unique coupled piezoelectric and semiconducting properties of zinc oxide nanostructures, which produce small electrical charges when they are flexed.

Fabrication begins with growing an array of vertically-aligned nanowires approximately a half-micron apart on gallium arsenide, sapphire or a flexible polymer substrate. A layer of zinc oxide is grown on top of substrate to collect the current. The researchers also fabricate silicon “zig-zag” electrodes, which contain thousands of nanometer-scale tips made conductive by a platinum coating.

The electrode is then lowered on top of the nanowire array, leaving just enough space so that a significant number of the nanowires are free to flex within the gaps created by the tips. Moved by mechanical energy such as waves or vibration, the nanowires periodically contact the tips, transferring their electrical charges. By capturing the tiny amounts of current produced by hundreds of nanowires kept in motion, the generators produce a direct current output in the nano-Ampere range.

Wang and his group members Xudong Wang, Jinhui Song and Jin Liu expect that with optimization, their nanogenerator could produce as much as 4 watts per cubic centimeter – based on a calculation for a single nanowire. That would be enough to power a broad range of nanometer-scale defense, environmental and biomedical applications, including biosensors implanted in the body, environmental monitors – and even nanoscale robots.

Nearly a year ago, in the April 14, 2006 issue of the journal Science, Wang’s research team announced the concept behind the nanogenerators. At that time, the nanogenerator could harvest power from just one nanowire at a time by dragging the tip of an atomic force microscope (AFM) over it. Made of platinum-coated silicon, the tip served as a Schottky barrier, helping accumulate and preserve the electrical charge as the nanowire flexed – and ensuring that the current flowed in one direction.

With its multiple conducting tips similar to those of an AFM, the new zig-zag electrode serves as a Schottky barrier to hundreds or thousands of wires simultaneously, harvesting energy from the nanowire arrays.

“Producing the top electrode as a single assembly sets the stage for scaling up this technology,” Wang said. “We can now see the steps involved in moving forward to a device that can power real nanometer-scale applications.”

Before that happens, additional development will be needed to optimize current production. For instance, though nanowires in the arrays can be grown to approximately the same length – about one micron – there is some variation. Wires that are too short cannot touch the electrode to produce current, while wires that are too long cannot flex to produce electrical charge.

“We need to be able to better control the growth, density and uniformity of the wires,” Wang said. “We believe we can make as many as millions or even billions of nanowires produce current simultaneously. That will allow us to optimize operation of the nanogenerator.”

In their lab, the researchers aimed an ultrasound source at their nanogenerator to measure current output over slightly more than an hour. Though there is some fluctuation in output, the current flow was continuous as long as the ultrasonic generator was operating, Wang said.

To rule out other sources of the current measured, the researchers substituted carbon nanotubes – which are not piezoelectric – for the zinc oxide nanowires, and used a top electrode that was flat. In both cases, the resulting devices did not produce current.

Providing power for nanometer-scale devices has long been a challenge. Batteries and other traditional sources are too large, and tend to negate the size advantages of nanodevices. And since batteries contain toxic materials such as lithium and cadmium, they cannot be implanted into the body as part of biomedical applications.

Because zinc oxide is non-toxic and compatible with the body, the new nanogenerators could be integrated into implantable biomedical devices to wirelessly measure blood flow and blood pressure within the body. And they could also find more ordinary applications.

Georgia Institute of Technology

Leading Scientists Announce Creation Of Encyclopedia Of Life

2007-05-10T19:04:00.000+02:00

Realizing a dream articulated in 2003 by renowned biologist E.O. Wilson, Harvard and four partner institutions have launched an ambitious effort to create an Encyclopedia of Life (EOL), an unprecedented project to document online every one of Earth's 1.8 million known species. For the first time in history, the EOL would grant scientists, students, and others multimedia access to all known living species, even those just discovered.

The effort will be supported by a new $10 million grant from the John D. and Catherine T. MacArthur Foundation and $2.5 million from the Alfred P. Sloan Foundation.

With a Wikipedia-style Web page detailing each organism's genome, geographic distribution, phylogenetic position, habitat, and ecological relationships, organizers hope the EOL will ultimately serve as a global beacon for biodiversity and conservation.

Harvard joins the Field Museum in Chicago, the Marine Biological Laboratory in Woods Hole, Mass., the Smithsonian Institution, and the Biodiversity Heritage Library (BHL) to initiate the project, bringing together species and software experts from across the world. An international advisory board of distinguished individuals will help guide the EOL.

Harvard's EOL participation will be led by James Hanken, director of Harvard's Museum of Comparative Zoology and Alexander Agassiz Professor of Zoology in the Faculty of Arts and Sciences. Harvard scientists will partner with colleagues at the Smithsonian to spearhead the education and outreach facets of the project.

"EOL is an audacious project, but one that is doable with existing technology," Hanken says. "It has the potential to transform how people learn and communicate about biology."

For more than 250 years, scientists have catalogued life, but traditional catalogues have long since become unwieldy, EOL organizers say. They believe technology can help science grasp the immense complexity of life on this planet while protecting Earth's biodiversity and better conserving our natural heritage.

Over the next 10 years, the EOL will create Web pages for all 1.8 million living species known to exist on Earth. The pages, housed at http://www.eol.org, will provide written information and, when available, photographs, video, sound, location maps, and other multimedia information on each species. Built on the scientific integrity of thousands of experts around the globe, the EOL will be a moderated Wikipedia-like resource, freely available to all users everywhere.

A prolific and eloquent author and perhaps the world's foremost champion of biodiversity, Wilson, the Pellegrino University Professor Emeritus at Harvard and now the honorary chair of the EOL, cheers the project's advent.

"Our knowledge of biodiversity is so incomplete that we are at risk of losing a great deal of it before it is ever discovered," he says, adding the hope "that we will work together to help create the key tool that we need to inspire preservation of Earth's biodiversity: the Encyclopedia of Life.

"What excites me is that since I first put forward this idea, science has advanced, technology has moved forward," Wilson says. "Today, the practicalities of making this encyclopedia real are within reach as never before."

Scientists began creating individual Web pages for species in the 1990s. However, Internet technology needed to mature to allow efficient creation of a comprehensive encyclopedia. While specific EOL efforts, including the scanning of key research publications and data, have been under way since January 2006, work has accelerated with the support of the John D. and Catherine T. MacArthur Foundation.

Ultimately, the EOL will be made available in numerous languages and will connect scientific communities concerned with ants, apples, or zebras. While initial work will emphasize species of animals, plants, and fungi, the design can be extended to encompass microbial life.

To provide depth behind the portal page for each species, the Biodiversity Heritage Library, a consortium that holds most of the relevant scientific literature, will scan and digitize tens of millions of pages of the scientific literature that will offer open access to detailed knowledge. In fact, the BHL already has scanning centers operating in London, Boston, and Washington, D.C., which have scanned the first 1.25 million pages for the EOL.[JH1]

"I dream that in a few years, wherever a reference to a species occurs on the Internet, there will be a hyperlink to its page in the Encyclopedia of Life," says James Edwards, executive secretary of the Global Biodiversity Information Facility and executive director of the EOL.

Note: This story has been adapted from a news release issued by Harvard University.

Science Daily

Examination of radiation left from birth of universe could alter theories

2007-05-09T18:54:00.000+02:00

Using relic radiation from the birth of the universe, astrophysicists at the University of Illinois have proposed a new way of measuring the fine-structure constant in the past, and comparing it with today.

By focusing on the absorption of the cosmic microwave background by atoms of neutral hydrogen, the researchers say, they could measure the fine-structure constant during the “dark ages,” the time after the Big Bang before the first stars formed, when the universe consisted mostly of neutral hydrogen and helium.

The fine-structure constant characterizes the strength of the electromagnetic force, which is one of the four fundamental forces in physics. But, the fine-structure constant may not be constant. Recent observations of quasars – starlike objects billions of light-years away – have found a slightly different value for the fine-structure constant.

“If the fine-structure constant does vary over time and space, we could use it as a probe of new physics beyond the standard model and beyond general relativity,” said Benjamin Wandelt, a cosmologist at Illinois, who developed the proposed measurement technique with graduate student Rishi Khatri.

A varying fine-structure constant also could help explain the mysterious dark energy that pervades the universe, Wandelt said, and help constrain what kind of theory would unite the four fundamental forces into a “theory of everything.”

Using light from quasars, astronomers can look for variations in the fine-structure constant from the present up to 5 billion years ago. Using the spectra of neutral hydrogen, astronomers can peer much further back in time.

“There is a void from about 300,000 years after the Big Bang, when radiation that formed the cosmic microwave background was emitted, to about 500 million years later, when the first stars formed,” Wandelt said. “Our measurement technique could probe the fine-structure constant during this period, known as the dark ages.”

When a neutral hydrogen atom absorbs a photon of light from the cosmic microwave background, the electron flips its spin, causing a slight difference in its spectrum.

The telltale fingerprint of this atomic transition at a wavelength of 21 centimeters can serve as a sensitive search for past values of the fine-structure constant, said Wandelt and Khatri, who describe their measurement technique in a paper accepted for publication in the journal Physical Review Letters, and posted on its Web site.

While most radio telescopes are too small to look for variations in the fine-structure constant, there are new instruments in the design or construction phase – including the Long Wavelength Array and the Low Frequency Array – that will provide the first limits when brought on line.

“The measurements would be tricky, but not impossible,” Wandelt said.

University of Illinois at Urbana-Champaign

China's earliest modern human

2007-05-09T14:00:00.000+02:00

Researchers at WUSTL and the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing have been studying a 40,000-year-old early modern human skeleton found in China and have determined that the "out of Africa" dispersal of modern humans may not have been as simple as once thought.

Erik Trinkaus, Ph.D., the Mary Tileston Hemenway Professor of anthropology in Arts & Sciences, his colleague Hong Shang, and others at the IVPP examined the skeleton, recovered in 2003 from the Tianyuan Cave, Zhoukoudian, near Beijing City.

The skeleton dates to 42,000 to 38,500 years ago, making it the oldest securely dated modern human skeleton in China and one of the oldest modern human fossils in eastern Eurasia.

The find could help explain how early man moved across Europe and Asia towards the East, a movement that is not completely understood by anthropologists.

The "Out of Africa" theory proposes that modern humans evolved in Africa and then spread throughout the earth somewhere around 70,000 years ago, replacing earlier humans with little or no interbreeding.

The specimen is basically a modern human, but it does have a few archaic characteristics, particularly in the teeth and hand bone. According to Trinkaus, this morphological pattern implies that a simple spread of modern humans from Africa is unlikely, especially since younger specimens have been found in Eastern Eurasia with similar feature patterns.

According to Trinkaus and Shang, "the discovery promises to provide relevant paleontological data for our understanding of the emergence of modern humans in eastern Asia."

They argue that the most likely explanation for the mix of features is interbreeding between early modern humans and the archaic populations of Europe and Asia.

Washington University in St. Louis

NASA's Chandra Sees Brightest Supernova Ever

2007-05-08T19:19:00.000+02:00

The brightest stellar explosion ever recorded may be a long-sought new type of supernova, according to observations by NASA's Chandra X-ray Observatory and ground-based optical telescopes. This discovery indicates that violent explosions of extremely massive stars were relatively common in the early universe, and that a similar explosion may be ready to go off in our own galaxy.

"This was a truly monstrous explosion, a hundred times more energetic than a typical supernova," said Nathan Smith of the University of California at Berkeley, who led a team of astronomers from California and the University of Texas in Austin. "That means the star that exploded might have been as massive as a star can get, about 150 times that of our sun. We've never seen that before."

Astronomers think many of the first generation of stars were this massive, and this new supernova may thus provide a rare glimpse of how the first stars died. It is unprecedented, however, to find such a massive star and witness its death. The discovery of the supernova, known as SN 2006gy, provides evidence that the death of such massive stars is fundamentally different from theoretical predictions.

"Of all exploding stars ever observed, this was the king," said Alex Filippenko, leader of the ground-based observations at the Lick Observatory at Mt. Hamilton, Calif., and the Keck Observatory in Mauna Kea, Hawaii. "We were astonished to see how bright it got, and how long it lasted."

The Chandra observation allowed the team to rule out the most likely alternative explanation for the supernova: that a white dwarf star with a mass only slightly higher than the sun exploded into a dense, hydrogen-rich environment. In that event, SN 2006gy should have been 1,000 times brighter in X-rays than what Chandra detected.

"This provides strong evidence that SN 2006gy was, in fact, the death of an extremely massive star," said Dave Pooley of the University of California at Berkeley, who led the Chandra observations.

The star that produced SN 2006gy apparently expelled a large amount of mass prior to exploding. This large mass loss is similar to that seen from Eta Carinae, a massive star in our galaxy, raising suspicion that Eta Carinae may be poised to explode as a supernova. Although SN 2006gy is intrinsically the brightest supernova ever, it is in the galaxy NGC 1260, some 240 million light years away. However, Eta Carinae is only about 7,500 light years away in our own Milky Way galaxy.

"We don't know for sure if Eta Carinae will explode soon, but we had better keep a close eye on it just in case," said Mario Livio of the Space Telescope Science Institute in Baltimore, who was not involved in the research. "Eta Carinae's explosion could be the best star-show in the history of modern civilization."

Supernovas usually occur when massive stars exhaust their fuel and collapse under their own gravity. In the case of SN 2006gy, astronomers think that a very different effect may have triggered the explosion. Under some conditions, the core of a massive star produces so much gamma ray radiation that some of the energy from the radiation converts into particle and anti-particle pairs. The resulting drop in energy causes the star to collapse under its own huge gravity.

After this violent collapse, runaway thermonuclear reactions ensue and the star explodes, spewing the remains into space. The SN 2006gy data suggest that spectacular supernovas from the first stars - rather than completely collapsing to a black hole as theorized - may be more common than previously believed.

"In terms of the effect on the early universe, there's a huge difference between these two possibilities," said Smith. "One pollutes the galaxy with large quantities of newly made elements and the other locks them up forever in a black hole."

Chandra X-ray Observatory

Scientists Offer New View of Photosynthesis

2007-05-08T18:41:00.000+02:00

During the remarkable cascade of events in photosynthesis, plants approach the pinnacle of stinginess by scavenging nearly every photon of available light energy to produce food.Yet after many years of careful research into the exact mechanisms, some key questions remain about this fundamental biological process that supports almost all life on Earth.

Now a research team led by Neal Woodbury, a scientist at the Arizona State University (ASU) Biodesign Institute, has come up with a new insight into the mechanism of photosynthesis.

The discovery involves the orchestrated movement of proteins on the timescale of a millionth of a millionth of a second.

"This pioneering research gives us new insights into the basic mechanism of photosynthesis," said Kamal Shukla, program director in the National Science Foundation (NSF) Division of Molecular and Cellular Biosciences. "Understanding such basic biological processes can lead to important societal benefits."

For example, the answer may be good news for the development of organic solar cells, said Shukla, which have been of commercial interest because of their relatively low cost compared to traditional silicon solar cells.

Traditional solar cells use semi-conductor devices (silicon chemistry) to convert solar energy into electricity, whereas organic solar cells are based on biological systems that use the same chemistry as living organisms to harvest the energy of sunlight to drive photosynthesis.

So, inspiration for the design of organic solar cells would be based upon the principle of photosynthesis.

Woodbury's research is focused on understanding the basic principles of photosynthesis and it could be valuable in the design of organic solar cells. The efficiency of energy conversion by photosynthesis is much higher than traditional solar devices.

To get a closer look at what happens during photosynthesis, the research team used a well-studied purple photosynthetic bacterium named Rhodobacter sphaeroides. This organism is likely one of the earliest photosynthetic bacteria to evolve.

The researchers focused their efforts on studying the center stage of photosynthesis, the reaction center, where light energy is funneled into specialized chlorophyll-binding proteins.

Woodbury and his colleagues tried to uncover more of the physical mechanism driving photosynthesis by creating mutants that would tweak the electron transfer relationships between molecules in the reaction center.

The researchers started to inch closer to an answer when Haiyu Wang, a postdoctoral research associate in Woodbury's lab, noticed something in common with all of the different mutants: a similarity in how fast electrons moved in the reaction center. He decided that there must be some sort of underlying physical principle involved.

Few research groups are equipped to measure the early events in photosynthesis because of the extremely short timescale--similar to the amount of time it takes a supercomputer to carry out a single flop.

Wang used ASU's ultrafast laser facility, funded by NSF, which acts like a high-speed motion picture camera that can capture data from these lightning-fast reactions.

The movement of the reaction center proteins during photosynthesis allows a plant or bacteria to harness light energy efficiently, even if conditions aren't optimal.

National Science Foundation (NSF)

How Plants Manage Calcium May Reduce Effects of Acid Rain

2007-05-07T23:42:00.000+02:00

A new understanding of how plants manage their internal calcium levels could lead to modifying plants to avoid damage from acid rain. The pollutant disrupts calcium balance in plants by leaching significant amounts of the mineral from leaves as well as the agricultural and forest soils the plants live in.

"Our findings should help scientists understand how plant ecosystems respond to soil calcium depletion and to design appropriate strategies to protect the environment," said Zhen-Ming Pei, a Duke University biologist who led the study, which is published in the March 9, issue of the journal Science."

The research was supported by the National Science Foundation (NSF), the U.S. Department of Agriculture and Xiamen University in China.

To grow, a plant needs a reliable supply of calcium, which enters the plant dissolved in water the roots take in from surrounding soil. As the water circulates through a plant, dissolved calcium gets shuttled where it is needed to give the plant's cells their structural rigidity. But calcium supplies coming into the plant cycle up and down over the course of the day, dropping to a minimum at night.

"Calcium is a key regulator of vital physiological functions in both plants and animals," said Maryanna Henkart, director of NSF's Division of Molecular and Cellular Biosciences. "The discovery of the relationship between calcium in soil, in plant cells, and cellular mechanisms sheds new light on the role of this important mineral in plant growth and development."

Plants use molecular sensors and flows of chemical messengers to detect and regulate the storage and distribution of vital nutrients such as water and calcium. To track the calcium sensors in the laboratory plant Arabidopsis, Pei and his coworkers used molecules originally found in jellyfish that emit light in the presence of calcium. To deduce the calcium sensor's role, the researchers also introduced an altered version of the sensor protein that abolishes the sensor's effects.

According to Pei, the sensors try to detect how much calcium there is and coordinate that level with growth and development. "If the sensors detect there is not enough calcium, they may tell the plant to hold off on growing, at least until it gets more calcium."

Although acid rain robs soil of much of its calcium, enough is still left for plants to live on, Pei added. But he suspects that sensors may misinterpret "less" as "too little" in those plants and unnecessarily signal for growth shutdowns.

"Some soils have lost as much as 75 percent of their calcium during the past century," Pei said. "One way to respond is to add new calcium to the soil. But we can't do that everywhere that it's needed, and it is also expensive. Perhaps a plant's calcium sensors could instead be tricked into interpreting "less" as "still enough" and keep building new cell walls."

Other Duke researchers who participated in the current study were postdoctoral researchers Ru-Hang Tang and Shengcheng Han; Hailei Zheng, a visiting professor from Xiamen University; Charles Cook, a laboratory technician; Christopher Choi, an undergraduate student; Todd Woerner, a chemistry instructor; and Robert Jackson, a biologist and director of Duke's Center on Global Change.

National Science Foundation (NSF)

Archaeologists Reveal Ancient Solar Observatory in Peru

2007-05-07T20:30:00.000+02:00

Solar calendars and sun cults were an important part of indigenous American culture, from the Hopi to the Inca sun temple in Cusco, Peru. The latest issue of Science features a new discovery at Chankillo, in the Casma Valley of Peru's coastal desert, pushing sun cults in the region back nearly 2,000 years.

A line of structures known as the 13 towers run north-south along the ridge of a low hill at Chankillo, a ceremonial center dating back to the fourth century B.C. From evident observation points on either side, the towers form a "toothed" horizon that spans the annual rising and setting arcs of the sun, indicating their use in solar observations.

"Chankillo is arguably the oldest solar calendar that can be identified as such with confidence within the Americas," said Ivan Ghezzi (Pontificia Universidad Catolica del Peru), who coauthored the Science paper with Clive Ruggles (University of Leicester).

Starting in 2000, Earthwatch volunteer teams assisted Ghezzi at Chankillo for three years, conducting excavations that supported this new revelation about the site's importance in ancient sun cults. They assisted in mapping the 13 towers, recording their alignments, and excavating the "solar observatory" to the west. Earthwatch volunteers also took tree ring samples from well-preserved wooden lintels that helped date the site.

"Many indigenous American sites have been found to contain one or a few putative solar orientations," continued Ghezzi. "Chankillo, in contrast, provides a complete set of horizon markers and two unique and indisputable observation points."

Excavation of ancient buildings to the west of the towers revealed one corridor that was clearly an observation point for watching the sun rise over the toothed horizon. The end of the corridor was littered with offerings of pottery, shell, and stone artifacts not found elsewhere nearby, indicating significant rituals associated with solar observations. A building to the east is in the exact mirror position of the western observation point, and is lined up to view the sunsets over the 13 towers.

The gaps between the towers are wide enough for just one or two sunrises to be observed in each. The regularity of the gaps suggests that the year was divided into regular intervals.

Plazas near the 13 towers apparently provided a setting for people participating in public rituals and feasts directly linked to solar observations. However, the observation points themselves appear to have been highly restricted to individuals with special status. This, along with ceramic warrior figurines found at the site, suggest the authority of an elite few. As with the Inca empire, two millennia later, sun worship and cosmology may have helped legitimize that authority.

"Chankillo was built approximately 1700 years before the Incas began their expansion," said Ghezzi. "Although there is obviously no direct culture-historical relationship between the 13 Towers of Chankillo and the sun pillars of Cuzco, they are analogous as horizon markers for calendrical purposes. Now we know these practices are quite a bit older, and were highly developed by Chankillo's time."

Earthwatch Institute

Unique Data Collected on Double Asteroid Antiope

2007-05-07T14:26:00.000+02:00

Combining precise observations obtained by ESO's Very Large Telescope with those gathered by a network of smaller telescopes, astronomers have described in unprecedented detail the double asteroid Antiope, which is shown to be a pair of rubble-pile chunks of material, of about the same size, whirling around one another in a perpetual pas de deux. The two components are egg-shaped despite their very small sizes.

The asteroid (90) Antiope was discovered in 1866 by Robert Luther from Dusseldorf, Germany. The 90th asteroid ever discovered, its name comes from Greek mythology. In 2000, William Merline and his collaborators found that the asteroid was composed of two similarly-sized components, making it a truly 'double' asteroid, one of the very first of this kind in the main belt of asteroids that lies between the orbits of Mars and Jupiter.

"The way double asteroids have formed in the main belt is still unclear," says Pascal Descamps, from the Paris Observatory and lead-author of the paper presenting the new results. "The Antiope system provides us with a unique opportunity to know more about this class of objects and we decided to study it in detail," he adds.

Descamps, with colleague Franck Marchis from the University of California at Berkeley, USA, therefore initiated a large campaign of observations for more than two and a half years starting in January 2003. They used the NACO instrument on ESO's Very Large Telescope at Cerro Paranal for the larger part, while using one of the Keck telescopes for some additional observations in 2005.

NACO allows the astronomers to perform adaptive optics observations, providing images that are mostly free from the blurring effect of the atmosphere. With these, it was always possible to separate clearly the two components of the Antiope system, thereby obtaining a large set of very precise measurements of their positions.

"With this unique set of data, we could determine with utmost precision the course of the two pieces of cosmic rock as they turn around each other," says Marchis. "We found that the two objects are separated by 171 km, and that they perform their celestial dance in 16.5 hours. In fact, we now know this orbital period with a precision of better than half a second."

With the orbit determined, the astronomers could derive the total mass of the system: 828 millions million tons, and found the two objects were rotating around their own axes at the same speed as they orbit each other. Thus, in the same way than the Moon does to the Earth, they always present to each other the same side (something astronomers call 'tidal locking'). Moreover, the two asteroids rotate in the same plane as they orbit each other.

The adaptive optics observations could, however, never resolve the shape of the individual components as they are too small. "But with the new orbit, we could precisely predict that from the end of May to the end of November 2005 the system would present eclipses and occultations," says Marchis. "Such 'mutual events' are unique opportunities to learn a great deal about this double asteroid."

The astronomers invited observers around the world to turn their eyes on the asteroid pair to measure the drops in brightness resulting from the predicted events. Over the six-month period, amateurs and professionals from as far afield as Brazil, Chile, France, Réunion Island, South Africa, and the USA, observed repeated occultations as well as shadows passing over one of the pair.

With this new data, Descamps, Marchis and their team, found enough evidence that the two mountain-like chunks of material forming the Antiope system have the shape of ellipsoids, that is, slightly deformed spheres, almost similar in size: 93.0 x 87.0 x 83.6 km and 89.4 x 82.8 x 79.6 km, respectively. Each asteroid in the pair is thus roughly the size of a large city.

Perhaps the most astonishing result is the fact that the two components have a shape close to the one predicted by the French scientist Edouard Roche in 1849 for self-gravitating, rotating fluid objects orbiting each other and tidally locked.

Of course, the asteroids are not gaseous nor liquids, they are solids, but their internal structure must be so loose that their bodies can readjust themselves due to the gravitational influence of the companion.

The scientists were also able to derive the density of the objects, only a quarter higher than the density of water. This means the asteroids are very porous, having 30 percent empty space, and thereby suggesting a rubble-pile structure. This structure could explain why it was easier for the asteroids to reach equilibrium shapes, while being so small.

"Despite this intensive study, the origin of this unique doublet still remains a mystery," says Descamps. "The formation of such a large double system is an improbable event and represents a formidable challenge to theory. One possibility is that a parent body was spun up so much that it took the shape of an apple core, then split into two similar-sized pieces."

European Southern Observatory

Finding Evidence of First Plate Tectonics 3.8 Billion Years Ago

2007-05-06T20:45:00.000+02:00

Identification of the oldest preserved pieces of Earth's crust in southern Greenland has provided evidence of active plate tectonics as early as 3.8 billion years ago, according to a report by an international team of geoscientists in the March 23 edition of Science magazine.

The finding pushes back the date of continent-forming processes previously determined as 2.5 billion years ago to a much earlier era considerably closer to Earth's formation some 4.5 billion years ago. Geochemical analysis of rocks has previously suggested an earlier date for plate tectonics, but this is the first study to find physical evidence of tectonics among Earth's oldest known rock structures, according to Hubert Staudigel of Scripps Institution of Oceanography at UC San Diego.

"The fact that this rock structure is so well preserved is particularly lucky," Staudigel said. "The materials were formed as seafloor along a spreading center and accreted to a continental plate and just stuck there, surviving almost unscathed for as long as 3.8 billion years."

Coauthors of the report are Harald Furnes of University of Bergen, Norway; Maarten de Wit of University of Cape Town, South Africa; Minik Rosing of the University of Copenhagen, Denmark; and Karlis Muehlenbachs of the University of Alberta, Canada.

The study focuses on an area near the southwestern coast of Greenland where there is a rare outcrop of ancient rock, called the Isua Supracrustal Belt, which have been dated at 3.8 billion years old. The Isua rocks are ophiolites, which have a green hue from the chlorite minerals within them and are found in all major mountain belts, usually located in areas associated with volcanism and plate tectonics. The Isua deposits were first described in the 1960s. They also have been found to contain fossilized evidence of the earliest bacterial life on Earth, also about 3.8 billion years old, in studies conducted in 1999 by Minik Rosing.

The new study reveals the geological structure at Isua contains both seafloor pillow lavas and dikes, or sheets, of basalt that intruded into the pillow lavas after they formed. These features and the chemistry of the ophiolites indicate that the area was formed as the result of seafloor spreading, according to lead author Furnes. Even though the rocks have physically changed over time, it is still possible to see their original characteristics because of the preservation of fine-grained crystals that show they were cooled by contact with surrounding colder rocks, Furnes said.

"To what extent one is able to see an original structure in a highly deformed rock depends basically on the experience of the observer," Furnes said. "In our case we knew what we were looking for, and all of us who did the field work have reasonably good experience with identifying pillow lavas and associated dikes."

The finding of ophiolites in the oldest known rock structures leads the scientists to believe that such rocks have formed throughout Earth's nearly 4.5 billion year history, according to de Wit.

"Our work shows that some form of seafloor spreading and oceanic crust formation occurs as far back in history as geological records go," de Wit said.

Rosing said, "Our paper describes large-scale structural relationships that show the ancient oceanic crust was comparable to the modern crust in its structure and composition and that a section of ancient oceanic crust could be preserved by uplifting onto stable crust, similar to how more modern ophiolite complexes have formed."

The paper also sheds light on the ongoing debate about the oxygen isotope composition of seawater through geological time periods. The reactions of seafloor and seawater largely control the ocean's oxygen isotope makeup, but scientists have been polarized between those that maintain the oxygen isotope content has remained relatively constant and those that argue for variation. According to Muehlenbachs, this work shows that the early ocean had the same or slightly heavier oxygen isotope composition as that of the modern ocean.

"We can conclude from the oxygen isotope analyses of the pillows and dIkes that the earliest ocean had already chemically reacted with the seafloor," Muehlenbachs said. "This has great implications to the historical chemical composition of the oceans and may have played a role in the evolution of life."

The geological processes of the early Earth were largely responsible for the distribution of elements throughout the land, air and oceans, having fundamental consequences for the development of life, according to Staudigel. He said the science team was sampling the Isua Supracrustal Belt looking for chemical or isotopic traces of life in the pillow lavas when they realized the area supplied geological structures proving plate tectonics from the earliest history of Earth.

The Norwegian Research Council, the Nordic Center for Earth Evolution, GeoForschungsZentrum Potsdam, Agouron Institute and the National Sciences and Engineering Research Council of Canada provided funding for the research.

Scripps Institution of Oceanography

Video

Staudigel and Tectonics

Man’s Earliest Direct Ancestors Looked More Apelike Than Previously Believed

2007-05-06T20:29:00.000+02:00

Modern man’s earliest known close ancestor was significantly more apelike than previously believed, a New York University College of Dentistry professor has found.

A computer-generated reconstruction by Dr. Timothy Bromage, a paleoanthropologist and Adjunct Professor of Biomaterials and of Basic Science and Craniofacial Biology, shows a 1.9 million-year-old skull belonging to Homo rudolfensis, the earliest member of the human genus, with a surprisingly small brain and distinctly protruding jaw, features commonly associated with more apelike members of the hominid family living as much as three million years ago.

Dr. Bromage’s findings call into question the extent to which H. rudolfensis differed from earlier, more apelike hominid species. Specifically, he is the first scientist to produce a reconstruction of the skull that questions renowned paleontologist and archeologist Richard Leakey’s depiction of modern man’s earliest direct ancestor as having a vertical facial profile and a relatively large brain - an interpretation widely accepted until now.

Dr. Bromage’s reconstruction also suggests that humans developed a larger brain and more vertical face with a less pronounced jaw and smaller teeth at least 300,000 years later than commonly believed, perhaps as recently as 1.6 million to one million years ago, when two later species, H. ergaster and H. erectus, lived. Dr. Bromage presented his findings at the annual scientific session of the International Association for Dental Research in New Orleans.

The fragmented skull Dr. Bromage reconstructed was originally discovered in Kenya in 1972 by Dr. Leakey, who reassembled it by hand and dated it at nearly three million years of age, an estimate revised to 1.9 million years by scientists who later discovered problems with the dating.

“Dr. Leakey produced a biased reconstruction based on erroneous preconceived expectations of early human appearance that violated principles of craniofacial development,” said Dr. Bromage, whose reconstruction, by contrast, shows a sharply protruding jaw and a brain less than half the size of a modern human’s. These characteristics make the 1.9 million-year-old early human skull more like those of two archaic, apelike hominids, Australopithecus and early Paranthropus, living at least three million and 2.5 million years ago, respectively.

Dr. Bromage developed his reconstruction according to biological principles holding that the eyes, ears, and mouth must be in precise relationship to one another in all mammals.

“Because he did not employ such principles, Dr. Leakey produced a reconstruction that could not have existed in real life,” Dr. Bromage concluded.

New York University

Fossil from 160,000 years ago shows growth profile similar to modern man

2007-05-05T14:36:00.000+02:00

An international team of scientists have found that the oldest member (160,000 years old) of the Homo sapiens species shows a life history profile similar to modern humans. These findings, based on experiments at ESRF, are in contrast to previous studies suggesting that early fossil humans possessed short growth periods, which were more similar to chimpanzees than to living humans.

The origins of modern humans continues to be one of the most hotly debated topics among anthropologists, and there is little consensus about where and when the first members of our species, Homo sapiens, became fully modern. While fossil evidence tells a complex tale of mosaic change during the African Stone Age, almost nothing is known about changes in human 'life history', or the timing of development, reproductive scheduling, and lifespan. Research during the past two decades has shown that early fossil humans (australopithecines and early Homo) possessed short growth periods, which were more similar to chimpanzees than to living humans. However, it is unclear when and in which group of fossil humans the modern condition of a relatively long childhood arose.

The North African fossil mandible superimposed over horizontal developmental lines on an incisor tooth, with the internal daily lines shown in the black and white image on the bottom. With this non-destructive technique it is now possible to accurately and non-destructively reconstruct how fossil teeth grew and how old juvenile individuals were when they died. The circular image on the left shows the organization of the third generation synchrotron at the European Synchrotron Radiation Facility in Grenoble, France, where the first ‘virtual tooth histology’ images were captured from fossil humans.

The team of scientists examined the tooth growth and eruption in a fossil from an 8 year old child using the unique tool that is the X-rays beams of the ESRF. The fossil is from one of the earliest representatives of Homo sapiens. It was found in Jebel Irhoud, Morocco and was dated to approximately 160,000 years ago.

The scientists come from the Max Planck Institute for Evolutionary Anthropology (Germany), the Laboratory of Geobiology, Biochronology and Human Paleontology in Poitiers (France), the ESRF (France), the School of Dental Sciences in Newcastle (United Kingdom), the Research School of Earth Sciences in Canberra (Australia) and from the Department of Geology of the Mohammed V-Agdal University in Rabat (Marocco).

Tooth growth, and most importantly first molar tooth eruption age, represents one of the most powerful clues to reconstruct growth processes in fossil humans. By using incremental growth lines in teeth, similar to annual rings in trees, developmental rate and time may be accurately established millions of years after death.

A) The North African juvenile fossil mandible showing the location of the incisor tooth enamel (white box) sampled with the Grenoble synchrotron. B) Close up of enamel fragment, with the area of interest (on right) shown in the white box. C) Synchrotron image showing growth lines (white arrows) with 10 daily lines between them (white brackets). The scale bar is 200 microns, or 0.2 mm.

The researchers used synchrotron light at the ESRF and combined a new application of a technique called phase imaging with developmental analysis. “It is the first non-destructive approach to characterize dental development with a high degree of precision, as synchrotron images reveal microscopic internal growth lines without damage to the sample”, explains Paul Tafforeau, one of the authors and developer of the virtual dental paleohistology using synchrotron light. Information on tooth growth in the Moroccan child was compared to other fossil and living human populations to determine if the modern condition of prolonged dental development was present.

These findings are not in contrast with our current wisdom that suggest that an extended period of development, and, by implication, childhood, may be linked to the origins of social, biological, and cultural changes needed to support dependent children with greater opportunities for early childhood learning.

European Synchrotron Radiation Facility (ESRF)

New form of matter-antimatter transformation observed for first time

2007-05-05T14:08:00.000+02:00

Whilst science fiction toys effortlessly with anti-matter, in reality it can be very hard to produce, so researchers around the world are celebrating a new break through in this area. For the first time, scientists using the BaBar experiment at the Stanford Linear Accelerator Center (SLAC) have observed the transition of one type of particle, the neutral D-meson, into its antimatter particle - a process known as 'mixing'. The new observation will be used as a test of the Standard Model, the current theory that best describes the entire universe's luminous matter and its associated forces.

UK BaBar spokesman, Fergus Wilson of the Rutherford Appleton Lab said "D-meson mixing was first predicted over three decades ago but it is such an elusive phenomenon that it has taken until today to see it. The observation of D-meson mixing is yet another outstanding achievement for the BaBar experiment. The BaBar collaboration continues to make ground-breaking measurements that challenge our understanding of how elementary particles behave."

"Achieving the large number of collisions needed to observe D-meson mixing is a testament to the tremendous capabilities of the laboratory's accelerator team," said SLAC Director Jonathan Dorfan. "The discovery of this long-sought-after process is yet another step along the way to a better understanding of the Standard Model and the physics beyond."

The PEP-II accelerator complex at SLAC, also known as the B Factory, allows the BaBar collaboration to study not only B-mesons but also several other types of particles including the D-meson. Mesons, of which there are about 140 types, are made up of fundamental particles called quarks, which can be produced when particles collide at high energy. A flurry of particles in a variety of combinations is produced when electrons and positrons smash together at high energy in the PEP-II collider facility. One of the most elusive results of this flurry is the transformation of one particle into its anti-particle in a process physicists call "mixing". Neutral K-mesons, observed more than 50 years ago, were the first elementary particles to demonstrate this phenomenon. About 20 years ago, scientists observed mixing with the B-meson. Now, for the first time, the BaBar experimenters have seen the D-meson transform into its anti-particle, and vice versa.

"This is a very exciting moment for us, having found the missing puzzle piece for particle-antiparticle mixing," said BaBar Spokesman Hassan Jawahery, a physics professor at the University of Maryland.

D-meson mixing is remarkably rare. Of the BaBar experiment's several billion recorded collisions, this study focuses on about a million events containing a D-meson decay that are candidates for this effect. The experimenters found about 500 events in which a D-meson had changed into an anti-D-meson before decaying.

By observing the rare process of D-meson mixing, BaBar collaborators can test the intricacies of the Standard Model. To switch from matter to antimatter, the D-meson must interact with "virtual particles," which through quantum fluctuations pop into existence for a brief moment before disappearing again. Their momentary existence is enough to spark the D-meson's transformation into an anti-D-meson. Although the BaBar detector cannot directly see these virtual particles, researchers can identify their effect by measuring the frequency of the D-meson to anti-D-meson transformation. Knowing that quantity will help determine whether the Standard Model is sufficient or whether it must be expanded to incorporate new physics processes.

"It's too soon to know if the Standard Model is capable of fully accounting for this effect, or if new physics is required to explain the observation," said Jawahery. "But in the coming weeks and months we are likely to see an abundance of new theoretical work to interpret what we've observed."

Some 600 scientists and engineers from 77 institutions in Canada, France, Germany, Italy, the Netherlands, Norway, Russia, Spain, the United Kingdom and the United States work on BaBar. SLAC is funded by the US Department of Energy's Office of Science. UK involvement is funded by PPARC.

Particle Physics and Astronomy Research Council (PPARC)

A New Theory of Climate Change

2007-05-05T13:50:00.000+02:00

In a review paper in the latest issue of the RAS journal Astronomy & Geophysics, Henrik Svensmark, the leader of Sun-climate research at the Danish National Space Center, puts together the findings reported by him and his colleagues in a dozen scientific papers, to tell how the climate is governed by atomic particles coming from exploded stars.

These cosmic rays help to make ordinary clouds. High levels of cosmic rays and cloudiness cool the world, while milder intervals occur when cosmic rays and cloud cover diminish.

The review paper entitled ‘Cosmoclimatology: a new theory emerges’ appears in the February issue of Astronomy & Geophysics. Here are some of its salient points.

For more than 20 years, satellite records of low-altitude clouds have closely followed variations in cosmic rays. Just how cosmic rays take part in cloud-making appeared in the SKY experiment, conducted in the basement of the Danish National Space Center. Electrons set free in the air by passing cosmic rays help to assemble the building blocks for cloud condensation nuclei on which water vapour condenses to make clouds.

Cosmic ray intensities – and therefore cloudiness – keep changing because the Sun’s magnetic field varies in its ability to repel cosmic rays coming from the Galaxy, before they can reach the Earth. Radioactive carbon-14 and other unusual atoms made in the atmosphere by cosmic rays provide a record of how cosmic-ray intensities have varied in the past. They explain repeated alternations between cold and warm periods during the past 12,000 years. Whenever the Sun was feeble and cosmic-ray intensities were high, cold conditions ensued, most recently in the Little Ace Age that climaxed 300 years ago.

On long timescales the intensity of cosmic rays varies more emphatically because the influx from the Galaxy changes. During the past 500 million years the Earth has passed through four ‘hothouse’ episodes, free of ice and with high sea levels, and four ‘icehouse’ episodes like the one we live in now, with ice-sheets, glaciers and relatively low sea levels.

Nir Shaviv of the Hebrew University in Jerusalem, together with Ján Veizer of the Ruhr University and the University of Ottawa, links these changes to the journey of the Sun and the Earth through the Milky Way Galaxy. They blame the icehouse episodes on encounters with bright spiral arms, where cosmic rays are most intense. More frequent chilling events, every 34 million years or so, occur whenever the solar system passes through with the mid-plane of the Galaxy.

In Snowball Earth episodes around 700 and 2300 million years ago, even the Equator was icy. At those times the birth-rate of stars in the Galaxy was unusually high, which would have also meant a large number of exploding stars and intense cosmic rays. Earlier still, the theory of cosmic rays and clouds helps to explain why the Earth did not freeze solid when it was very young. The Sun was much fainter than it is now, but also more vigorous in repelling cosmic rays, so the Earth would not have had much cloud cover.

While calculating the changing influx since life began about 3.8 billion years ago, Dr Svensmark discovered a surprising connection between cosmic-ray intensities and a variability of the productivity of life. The biggest fluctuations in productivity coincided with high star formation rates and cool periods in the Earth’s climate. Conversely, during a billion years when star formation was slow, cosmic rays were less intense and the Earth’s climate was warmer, the biosphere was almost unchanging in its productivity.

Near the end of his review Dr Svensmark writes: ‘The past 10 years have seen the reconnaissance of a new area of research by a small number of investigators. The multidisciplinary nature of cosmoclimatology is both a challenge and an opportunity for many lines of inquiry.’ Even the search for alien life is affected, because it should now take into account of the need for the right magnetic environment, if life is to originate and survive on the planets of other stars.

Royal Astronomical Society

First study reporting chimps using caves

2007-05-05T13:13:00.000+02:00

Chimpanzees in Senegal apparently have much in common with our earliest human ancestors.

A month after Iowa State University Assistant Professor of Anthropology Jill Pruetz reported chimpanzees at her Fongoli research site are using spear-shaped tools to hunt, her new study indicates those same chimps are also seeking shelter in caves to get out of the extreme African heat. The National Geographic Society-funded research is the first to document regular chimpanzee cave use.

Pruetz' paper, titled "Evidence of Cave Use by Savanna Chimpanzees (Pan troglodytes verus) at Fongoli, Senegal: Implications for Behavioral Thermoregulation," will be published in an upcoming issue of Primates, a professional journal.

The paper reports that the chimpanzees' cave use was based primarily on indirect evidence -- feeding traces, feces and hairs -- gathered from one cave from January through December 2004. Supplemental data from observational records was also collected from May 2001 through March 2006. Pruetz has also witnessed the chimps entering and exiting the cave.

"I talked about it (chimps using caves) at a meeting in Japan several years ago. I just kind of reported it and everyone was amazed," she said. "They thought it was great and nobody had ever heard anything like it, except that Jane Goodall actually came up to me after the talk and she said that she heard an incident in Mali where someone was doing a chimp survey and they surprised a bunch of chimps coming out of a cave. But that's the only other instance that anyone, as far as I know, has ever heard of it."

Chimps use caves to avoid African heat

In the paper, Pruetz concludes that the chimps' cave use is a response to heat at her Fongoli research site. She collected data on temperatures within Sakoto cave -- the largest cave within her site -- as well as the different habitats used by chimpanzees, such as gallery forest and woodland.

Her research found that chimps primarily use Sakoto cave as shelter during the hottest and driest times of the year, from October through May. The cave is several meters deep and located at the head of a shallow ravine, which was formed through water runoff from a plateau. Between 2001 and 2004, average annual daily temperature within the Sakoto cave was 24.2 degrees Celsius, compared with 29.6 degrees in the woodland habitat and 24.6 in grassland habitat -- both located approximately 30 meters from the cave and at the edge of the Sakoto ravine. Pruetz attributes the lower grassland temperature to wind. In the Sakoto gallery forest habitat approximately 20 meters from the cave, temperatures averaged 26.4 degrees Celsius.

"It seems very much cooler when you go into the cave, but I wanted to make sure I took temperature measurements in the cave and different habitats," said Pruetz. "It is significantly cooler in the cave and the only time they (chimps) use the cave is during the dry season when you have the hottest temperatures outside.

"They're (chimps) just using it as a way to avoid the heat," she said. "They just lie in there and rest. They'll bring food in and eat it in there, and groom. They sort of just hang out and relax."

Maximum temperatures produce primate heat stress

Pruetz wrote in the article that maximum temperatures may be a more important measure of heat stress to primates than average temperatures. And that stress may be what's driving the chimps into the caves, although the explanation may not be that simple.

"While cave use by Fongoli chimpanzees appears to correlate with temperature, a number of factors probably work in association to influence this behavior, underscoring the complexity of the relationship between climate, habitat, and the behavior of hominoids inhabiting a dry, open environment," she wrote.

But maybe it shouldn't be so surprising that chimpanzees are using caves after all.

"It shouldn't be surprising that chimps are using caves," said Pruetz. "If you look at the scientific name of the chimps, the species name is troglodytes, which means cave-dwelling."

Pruetz will return to Senegal in May. She and her Iowa State graduate students plan to measure relative humidity in the different habitats used in this research.

The study was supported by grants from the National Geographic Society, National Science Foundation, Leakey Foundation, U.S. Fish and Wildlife Great Ape Conservation Grant, Primate Conservation Inc., and Iowa State University.

Iowa State University

COROT discovers its first exoplanet and catches scientists by surprise

2007-05-04T21:41:00.000+02:00

COROT has provided its first image of a giant planet orbiting another star and the first bit of ‘seismic’ information on a far away, Sun-like star, with unexpected accuracy.The unanticipated level of accuracy of this raw data shows that COROT will be able to see rocky planets - perhaps even as small as Earth - and possibly provide an indication of their chemical composition.

The unanticipated level of accuracy of this raw data shows that COROT will be able to see rocky planets - perhaps even as small as Earth - and possibly provide an indication of their chemical composition.

COROT, a CNES project with ESA participation, is a mission with a dual goal. It is the first space mission dedicated entirely to the search of extra-solar planets. It provides a wide-field survey of planets like our own at an unprecedented level of accuracy. It is also making the most comprehensive study ever of the interior of stars other than our Sun. Both objectives are achieved by analysing the behaviour of light emitted by a target star.

An exoplanet is detected by COROT due to a sudden decrease in the intensity of light or the ‘light curve’ of a parent star when a planet transits in front of it.

The study of stellar interiors – or ‘asteroseismology’ – is carried out by analysing the oscillations in the light curve of the star. The oscillations are created due to mechanical waves propagating in the star itself and they give a clue to the structure of its interior.

COROT’s strength lies in the continued observation of the same targets in a given area of the sky. The observations have been on since the science operations began, 60 days ago. Another strong point is the accuracy with which it measures the variations in the luminosity of the star.

The first planet detected by COROT, now named ‘COROT-Exo-1b’, is a very hot gas giant, with a radius equal to 1.78 times that of Jupiter. It orbits a yellow dwarf star similar to our Sun with a period of about 1.5 days. ‘COROT-Exo-1b’ is situated roughly 1500 light years from us, in the direction of the constellation Unicorn (Monoceros). Coordinated spectroscopic observations from the ground have also allowed the determination of the mass of the planet, equivalent to about 1.3 Jupiter masses.

The scientific evaluation of the results that are streaming in will take some time. “The data we are presenting today is still raw but exceptional,” says Malcolm Fridlund, COROT Project Scientist for ESA. “It shows that the on-board systems are working better than expected in some cases - up to ten times the expectation before launch. This will have an enormous impact on the results of the mission.”

All the sources of noise and disturbance have not yet been taken into account in the data. This first exoplanet was detected with an error of only 0.0003 or 0.03% during one hour of observation.

On applying all the corrections to the light curves, the error will be reduced to only 5 parts out of 100 000. When many transits of the planet in front of the star are observed, the precision will approach just one or a few parts out of 100 000.

As a consequence, small planets down to the size of our Earth – three times smaller than initially thought possible - will be in the grasp of COROT. The satellite may also be able, in specific circumstances, to detect subtle variations in the stellar light reflected by the planet itself. This would give an indication of its chemical composition.

The quality of the asteroseismological data is equally impressive. Excellent ‘starquake’ data were obtained during the first 60 days of observations, with a margin of error of less than one part per million.

COROT observed a bright Sun-like star continuously for 50 days, showing large, unexpected luminosity variations on time scales of a few days. This may be related to the star’s magnetic activity.

The accuracy of these measurements was truly outstanding: with an error of five parts out of 100 000 in one minute (corresponding to one part per million over four minutes), COROT has already reached the maximum performance for a telescope of its size.

The preliminary analysis of the oscillations in stellar luminosity clearly shows the seismic signature typical of a Sun-like star. This analysis will eventually help scientists understand the star’s internal structure and age.

ESA New