Monday, November 2, 2009

GEOLOGISTS POINT TO OUTER SPACE AS SOURCE OF THE EARTH'S MINERAL RICHES

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According to a new study by geologists at the University of Toronto and the University of Maryland, the wealth of some minerals that lie in the rock beneath the Earth's surface may be extraterrestrial in origin.

"The extreme temperature at which the Earth's core formed more than four billion years ago would have completely stripped any precious metals from the rocky crust and deposited them in the core," said Professor James Brenan of geology at U of T and co-author of the study published in Nature Geoscience Oct. 18.

"So, the next question is why are there detectable, even mineable, concentrations of precious metals such as platinum and rhodium in the rock portion of the Earth today? Our results indicate that they could not have ended up there by any known internal process and instead must have been added back, likely by a 'rain' of extraterrestrial debris such as comets and meteorites."

Geologists have long speculated that four and a half billion years ago, the Earth was a cold mass of rock mixed with iron metal that was melted by the heat generated from the impact of massive planet-sized objects, allowing the iron to separate from the rock and form the Earth's core. Brenan and colleague William McDonough of the University of Maryland recreated the extreme pressure and temperature of this process, subjecting a similar mixture to temperatures above 2,000 C and measured the composition of the resulting rock and iron.

Because the rock became void of the metal in the process, the scientists speculate that the same would have occurred when the Earth was formed and that some sort of external source - such as a rain of extraterrestrial material - contributed to the presence of some precious metals in Earth's outer rocky portion today.

"The notion of extraterrestrial rain my also explain another mystery, which is how the rock portion of the Earth came to have hydrogen, carbon and phosphorous - the essential components for life, which were likely lost during Earth's violent beginning."

University of Toronto

ANCIENT LEMURS TAKE BITE OUT OF EVOLUTIONARY TREE

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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.

(Photo: Zina Deretsky, National Science Foundation)

National Science Foundation

DEEP-SEA MICROBES MAY ANSWER LONG-STANDING QUESTION ABOUT EARTH'S NITROGEN CYCLE

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Scientists have identified an unexpected metabolic ability in a symbiotic community of deep-sea microorganisms. It may help solve a lingering mystery about the world's nitrogen cycle.

The element nitrogen is a critical part of amino acids, the building blocks of proteins, and therefore essential to all life. Although nitrogen is plentiful on Earth--it represents 78 percent of the atmosphere, by volume--the element is usually found strongly bonded to itself.

To be biologically useful, a nitrogen atom must be released from this coupling and converted to a reduced, or "fixed," state; reduced nitrogen atoms gain an electron, which makes them chemically reactive.

Although lightning, combustion, and other non-biological processes can create reduced nitrogen, far more is generated by nitrogen-fixing microorganisms such as bacteria, in particular, photosynthetic aquatic cyanobacteria. These organisms produce the bulk of the nitrogen available to living things in the ocean.

When researchers add up all known sources of fixed nitrogen--biological and otherwise--in the global nitrogen cycle, and compare it to the sinks (biological uptake for growth and energy), they come up short.

More nitrogen appears to be used than is being made. The "nitrogen budget," in effect, does not balance.

The question has been whether the nitrogen cycle is out of balance, or whether the known inventories of sources and sinks are incomplete, says Victoria Orphan, a geobiologist at Caltech.

Orphan, along with Caltech graduate student Anne Dekas and Caltech postdoctoral researcher Rachel Poretsky, suggest the answer is, at least in part, an incomplete catalogue of the sources of fixed nitrogen.

A paper about their discovery appears in the journal Science.

The team studied ocean sediment samples in methane cold seeps 20 miles off northern California at a depth of 1,800 feet. The area, known as the Eel River Basin, is in a region that supports high levels of natural methane seepage at the sea-floor.

In the laboratory, the researchers examined the methane-rich sediment and the tiny microbial conglomerations that live within.

These spherical cell conglomerates, averaging 500 cells each, consist of two types of anaerobic microorganisms living in a unique symbiotic relationship fueled by methane.

The first is a bacterium that reduces the chemical sulfate into sulfide (the process that produces the rotten-egg odor of salt marshes and mud flats) to generate energy.

The second is a methane-oxidizing archaeon; the archaea are a group of non-bacterial single-celled microorganisms.

Working together, these two symbionts are responsible for consuming the majority of the naturally-released methane in the deep sea.

Although these symbiotic associations themselves are not new--the conglomerations were found about a decade ago--the scientists discovered something unexpected: the methane-consuming archaea were actively fixing nitrogen, and sharing it with their bacterial neighbors.

This is the first time nitrogen fixation has been documented in methane-oxidizing archaea, say the scientists.

"The past discovery that archaeal/bacterial consortia were the agents of methane oxidation led to a paradigm shift in our view of carbon cycling at the bottom of the ocean," says Matt Kane, program director in the National Science Foundation (NSF)'s division of environmental biology, which funded the research, along with NSF's division of ocean sciences. "This new finding extends that paradigm shift to the nitrogen cycle.

"Such discoveries are revolutionizing how we think about microbial physiological ecology and its impact on Earth's biogeochemical cycles."

Although the organisms have a nitrogen-poor diet of methane gas, they live in an environment that has reduced nitrogen in the form of ammonium and other chemicals, which means they shouldn't need to create their own.

It's possible that they do need to because they are living in a crowded community, say Orphan and colleagues, a tightly packed ball that prevents some organisms from having access to nitrogen.

The organisms have ultra-slow growth rates, doubling once every three to six months. "But they are passing on some nitrogen to their neighbors, which means they are producing more than they need, despite the energy cost of doing so," Dekas says.

"We don't know what benefit the archaeal organisms get from sharing it, but we know they need the bacterial symbiont to stay alive."

(Photo: Victoria Orphan, Caltech)

National Science Foundation

GEOLOGIST ANALYZES EARLIEST SHELL-COVERED FOSSIL ANIMALS

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The fossil remains of some of the first animals with shells, ocean-dwelling creatures that measure a few centimeters in length and date to about 520 million years ago, provide a window on evolution at this time, according to scientists. Their research indicates that these animals were larger than previously thought.

John Moore, a Ph.D. student in the Department of Earth Science at UC Santa Barbara, and his collaborators, analyzed fossils from the epoch called the Early Cambrian. During this important time in the history of the earth, there was a tremendous diversification of animal life in the oceans. Many of the major animal groups that are still alive today appeared at this time, as well as many unusual groups that went extinct. In particular, the Cambrian marked the first widespread occurrence of animals with shells or other hard parts. Many of these early animals had complex external armors containing dozens to thousands of tiny pieces. When the animals died, the armor fell apart. From the resulting jumbled puzzle pieces, Moore and his research team discerned what the animals were like, and how they are related to other animals.

"In our study, we focused on a strange Cambrian creature, called Cambrothyra," said Moore. He explained that Cambrothyra fossils look like tiny jars or vases, a few tenths of a millimeter long. They have been found in only a few locations in central China. The research team collected rocks from China's Shaanxi Province and brought them back to the lab where they extracted the fossils from the host rocks.

"While some scientists once thought that each little jar-like structure of Cambrothyra was the shell of a tiny single-celled protist, our work instead supports the hypothesis that Cambrothyra was an animal, probably a few centimeters long, that was covered with an armor that was made up of hundreds of separate tiny, jar-shaped pieces," said Moore. "In particular, Cambrothyra seems to be related to another unusual Cambrian animal, the chancelloriids, which were attached to the sea floor and looked a bit like barrel cacti –– although they were animals rather than plants which suggests that Cambrothyra may have been a relative." Cambrothyra also shares similarities with a different Cambrian group, the halkieriids. This animal looked like a slug covered with armor. It traveled around the sea floor and thus may help support the idea that chancelloriids and halkieriids are closely related to each other, despite very different appearances.

Moore presented his findings at the annual meeting of the Geological Society of America in Portland, Ore., today. He completed the work in collaboration with his advisor Susannah Porter, assistant professor in the Department of Earth Science at UCSB; Michael Steiner of the Freie Universität, Berlin; and Guoxiang Li of the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences.

(Photo: UCSB)

2-MILLION-YEAR-OLD EVIDENCE SHOWS TOOL-MAKING HOMININS INHABITED GRASSLAND ENVIRONMENTS

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In an article published in the open-access, peer-reviewed journal PLoS ONE on October 21, 2009, Dr Thomas Plummer of Queens College at the City University of New York, Dr Richard Potts of the Smithsonian Institution National Museum of Natural History and colleagues report the oldest archeological evidence of early human activities in a grassland environment, dating to 2 million years ago. The article highlights new research and its implications concerning the environments in which human ancestors evolved.

Scientists as far back as Charles Darwin have thought that adaptation to grassland environments profoundly influenced the course of human evolution. This idea has remained well-entrenched, even with recent recognition that hominin origins took place in a woodland environment and that the adaptive landscape in Africa fluctuated dramatically in response to short-term climatic shifts.
During the critical time period between 3 and 1.5 million years ago, the origin of lithic technology and archeological sites, the evolution of Homo and Paranthropus, selection for endurance running, and novel thermoregulatory adaptations to hot, dry environments in H. erectus have all been linked to increasingly open environments in Africa.

However, ecosystems in which grassland prevails have not been documented in the geological record of Pliocene hominin evolution, so it has been unclear whether open habitats were even available to hominins, and, if so, whether hominins utilized them. In their new study, Plummer and colleagues provide the first documentation of both at the 2-million-year-old Oldowan archeological site of Kanjera South, Kenya, which has yielded both Oldowan artifacts and well-preserved faunal remains, allowing researchers to reconstruct past ecosystems.

The researchers report chemical analyses of ancient soils and mammalian teeth, as well as other faunal data, from the ~2.0-million-year-old archeological sites at Kanjera South, located in western Kenya. The principal collaborating institutions of the Kanjera project are Queens College of the City University of New York, the Smithsonian Institution's Human Origins Program, and the National Museums of Kenya. The findings demonstrate that the recently excavated archeological sites that preserve Oldowan tools, the oldest-known type of stone technology, were located in a grassland-dominated ecosystem during the crucial time period.

The study documents what was previously speculated based on indirect evidence – that grassland-dominated ecosystems did, in fact, exist during the Plio-Pleistocene (ca. 2.5-1.5 million years ago) and that early human tool-makers were active in open settings. Other recent research shows that the Kanjera hominins obtained meat and bone marrow from a variety of animals and that they carried stone raw materials over surprisingly long distances in this grassland setting. A comparison with other Oldowan sites shows that by 2.0 million years ago, hominins, almost certainly of the genus Homo, lived in a wide range of habitats in East Africa, from open grassland to woodland and dry forest.

Plummer and colleagues conclude that early Homo was flexible in its habitat use and that the ability to find resources in both open and wooded habitats was a key part of its adaptation. This strongly contrasts with the habitat usage of older species of Australopithecus and appears to signify an important shift in early humans' use of the landscape.

(Photo: Thomas Plummer)

LOOKING FOR THE ORIGINS OF MUSIC IN THE BRAIN

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Origins of music perception in humans may have their foundation in animal communication calls, as evidenced here in non-human primates. Many speech sounds and animal vocalizations, for instance, contain components, commonly referred to as complex tones, which consist of a fundamental frequency (f0) and higher harmonics.

Using electrophysiological recording techniques to study the neuronal activities in the auditory cortex of awake monkeys, researchers at Georgetown University Medical Center's have shown neurons tuned to the fundamental frequencies and harmonic sounds, and such neural mechanisms of harmonic processing lay close to tonotopically organized auditory areas. They presented their findings at the 39th annual meeting Society of Neuroscience.

"The understanding of neural mechanism of 'innate' music features in non-human primates will facilitate an improved understanding of music perception in the human nervous system," explains Yuki Kikuchi, PhD, a research associate in the department of physiology and biophysics.

"This will allow a neurobiological framework from which to understand the basis of the effectiveness of music therapeutic interventions."

Georgetown University

THE LOTUS'S CLEVER WAY OF STAYING DRY

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An ancient Confucian philosopher once said, "I love the lotus because while growing from mud, it is unstained."

Now, almost one thousand years since Zhou Dunyi wrote these lines in China, scientists finally understand how the plant keeps itself clean and dry. It took an ultra high speed camera, a powerful microscope and an audio speaker to unlock a secret that has puzzled scientists for ages.

The process of solving this biological problem inspired Duke University engineers to make use of man-made surfaces resembling the lotus to improve the efficiency of modern engineering systems, such as power plants or electronic equipment, which must be cooled by removing heat through water evaporation and condensation.

For the first time, scientists were able to observe water as it condensed on the leaf's surface, and more importantly, how the water condensate left the leaf.

The trick lies in the surface of the plant's large leaves, and the subtle vibrations of nature. The leaves are covered with tiny irregular bumps spiked with even tinier hairs projecting upward. When a water droplet lands on this type of surface, it only touches the ends of the tiny hairs. The droplet is buoyed by air pockets below and ultimately is repelled off the leaf.

"We faced a tricky problem – water droplets that fall on the leaf easily roll off, while condensate that grows from within the leaf's nooks and crannies is sticky and remains trapped," said Jonathan Boreyko, a third-year graduate student at Duke's Pratt School of Engineering, who works in the laboratory of assistant professor Chuan-Hua Chen. The results of the team's experiments were published early on-line in the journal Physics Review Letters.

"Scientists and engineers have long wondered how these sticky drops are eventually repelled from the leaf after their impalement into the tiny projections," Boreyko said. "After bringing lotus leaves into the lab and watching the condensation as it formed, we were able to see how the sticky drops became unsticky."

The key was videotaping the process while the lotus leaf rested on top of the woofer portion of a stereo speaker at low frequency. Condensation was created by cooling the leaf. It turned out that after being gently vibrated for a fraction of a second, the sticky droplets gradually unstuck themselves and jumped off the leaf.

Voila, a dry leaf.

"This solves a long-standing puzzle in the field," Chen said. "People have observed that condensation forms every night on the lotus leaf. When they come back in the morning the water is gone and the leaf is dry. The speaker reproduced in the lab what happens every day in nature, which is full of subtle vibrations, especially for the lotus, which has large leaves atop long and slender stems."

The results of these experiments, as well as earlier ones showing for the first time that water droplets spontaneously "jump" off a highly water-repellent, or superhydrophobic, surface, will allow engineers to employ man-made surfaces much like the lotus leaf in settings where the removal of condensation and the transfer of heat are necessary.

We have revealed the physics behind anti-dew superhydrophobicity, a vital property for water-repellent materials to be deployed in the real world," Chen said. "These materials will be used in humid or cold environments where condensation will naturally occur. Our findings point to a new direction to develop water-repellent materials that would survive in demanding natural environments, and have strong implications for a variety of engineering applications including non-sticking textiles, self-cleaning optics and drag-reducing hulls."

(Photo: Duke University)

Duke University

GALAXY CLUSTER SMASHES DISTANCE RECORD

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The most distant galaxy cluster yet has been discovered by combining data from NASA's Chandra X-ray Observatory and optical and infrared telescopes. The cluster is located about 10.2 billion light years away, and is observed as it was when the Universe was only about a quarter of its present age.

The galaxy cluster, known as JKCS041, beats the previous record holder by about a billion light years. Galaxy clusters are the largest gravitationally bound objects in the Universe. Finding such a large structure at this very early epoch can reveal important information about how the Universe evolved at this crucial stage.

JKCS041 is found at the cusp of when scientists think galaxy clusters can exist in the early Universe based on how long it should take for them to assemble. Therefore, studying its characteristics – such as composition, mass, and temperature – will reveal more about how the Universe took shape.

"This object is close to the distance limit expected for a galaxy cluster," said Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy. "We don't think gravity can work fast enough to make galaxy clusters much earlier."

Distant galaxy clusters are often detected first with optical and infrared observations that reveal their component galaxies dominated by old, red stars. JKCS041 was originally detected in 2006 in a survey from the United Kingdom Infrared Telescope (UKIRT). The distance to the cluster was then determined from optical and infrared observations from UKIRT, the Canada-France-Hawaii telescope in Hawaii and NASA's Spitzer Space Telescope. Infrared observations are important because the optical light from the galaxies at large distances is shifted into infrared wavelengths because of the expansion of the universe.

The Chandra data were the final - but crucial - piece of evidence as they showed that JKCS041 was, indeed, a genuine galaxy cluster. The extended X-ray emission seen by Chandra shows that hot gas has been detected between the galaxies, as expected for a true galaxy cluster rather than one that has been caught in the act of forming.

Also, without the X-ray observations, the possibility remained that this object could have been a blend of different groups of galaxies along the line of sight, or a filament, a long stream of galaxies and gas, viewed front on. The mass and temperature of the hot gas detected estimated from the Chandra observations rule out both of those alternatives.

The extent and shape of the X-ray emission, along with the lack of a central radio source argue against the possibility that the X-ray emission is caused by scattering of cosmic microwave background light by particles emitting radio waves.

It is not yet possible, with the detection of just one extremely distant galaxy cluster, to test cosmological models, but searches are underway to find other galaxy clusters at extreme distances.

"This discovery is exciting because it is like finding a Tyrannosaurus Rex fossil that is much older than any other known," said co-author Ben Maughan, from the University of Bristol in the United Kingdom. "One fossil might just fit in with our understanding of dinosaurs, but if you found many more, you would have to start rethinking how dinosaurs evolved. The same is true for galaxy clusters and our understanding of cosmology."

The previous record holder for a galaxy cluster was 9.2 billion light years away, XMMXCS J2215.9-1738, discovered by ESA's XMM-Newton in 2006. This broke the previous distance record by only about 0.1 billion light years, while JKCS041 surpasses XMMXCS J2215.9 by about ten times that.

"What's exciting about this discovery is the astrophysics that can be done with detailed follow-up studies," said Andreon.

Among the questions scientists hope to address by further studying JKCS041 are: What is the build-up of elements (such as iron) like in such a young object? Are there signs that the cluster is still forming? Do the temperature and X-ray brightness of such a distant cluster relate to its mass in the same simple way as they do for nearby clusters?

(Photo: NASA/CXC/INAF/S.Andreon et al)

Harvard University

NEW EVIDENCE OF CULTURE IN WILD CHIMPANZEES

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A new study of chimpanzees living in the wild adds to evidence that our closest primate relatives have cultural differences, too. The study, reported online on October 22nd in Current Biology, a Cell Press publication, shows that neighboring chimpanzee populations in Uganda use different tools to solve a novel problem: extracting honey trapped within a fallen log.

Kibale Forest chimpanzees use sticks to get at the honey, whereas Budongo Forest chimpanzees rely on leaf sponges—absorbent wedges that they make out of chewed leaves.

"The most reasonable explanation for this difference in tool use was that chimpanzees resorted to preexisting cultural knowledge in trying to solve the novel task," said Klaus Zuberbühler of the University of St Andrews in Scotland. "Culture, in other words, helped them in dealing with a novel problem."

"Culture" in this sense refers to a population-specific set of behaviors acquired through social learning, such as imitation, Zuberbühler explained. That's in contrast to an animal or human learning something on his or her own through trial and error, without taking into account what others around them do, or behaviors that are "hard-wired" and require no learning at all.

Behavioral differences among animal populations have been taken as evidence of culture, the researchers said, but it's a notion that has remained controversial. Some think that other explanations—differences in the environment or in genetics—seem more likely.

Perhaps the strongest evidence for animal culture has come from studies on wild chimpanzees in Africa, Zuberbühler said. For instance, 15 years of field observation has shown that Kibale chimps habitually use sticks as tools, whereas Budongo chimps never do. Both groups make use of leaf sponges to access water from tree holes.

The question is, are those differences really cultural? That's been a hard question to answer because scientists couldn't rule out all of the possible ecological or genetic explanations for those behavioral differences. Scientists have seen social transmission of behaviors among chimpanzees living in captivity, with good evidence that the chimps can socially learn arbitrary behavior. It still wasn't clear whether those findings were relevant to chimps in the wild.

To help get around earlier limitations in the new study, Zuberbühler and his colleague Thibaud Gruber presented the two well-known chimpanzee groups with something that they hadn't seen before, in this case, honey trapped inside a narrow hole drilled into a log.

"With our experiment we were able to rule out that the observed differences in chimpanzee tool use behavior are the result of genetic differences because we tested members of the same subspecies," Zuberbühler said. They also ruled out habitat influences by exposing the chimps to the same unfamiliar problem.

Zuberbühler said that they were surprised by how quickly the animals found their respective solutions. "The cultural differences, in other words, must be deeply entrenched in their minds," he said.

Cell Press

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