Category: Reviews

1 Nov

Dating Evidence: Relics Could Be of John the Baptist

New dating evidence supports claims that bones found under a church floor in Bulgaria may be of John the Baptist, who is described in the Bible as a leading prophet and relative of Jesus Christ. A team from the Oxford Radiocarbon Accelerator Unit at Oxford University dated a knucklebone from the right hand to the 1st century AD, a date which fits with the widely held view of when he would have lived. The researchers say they were surprised when they discovered the very early age of the remains adding, however, that dating evidence alone cannot prove the bones to be of John the Baptist. The bones were originally discovered in 2010 by archaeologist Kazimir Popkonstantinov, excavating under an ancient church on an island in Bulgaria known as Sveti Ivan, which translates into English as St John. The knucklebone was one of six human bones, including a tooth and the face part of a cranium, found in small marble sarcophagus under the floor near the altar. Three animal bones were also inside the sarcophagus. Oxford professors Thomas Higham and Christopher Ramsey attempted to radiocarbon date four human bones, but only one of them contained a sufficient amount of collagen to be dated successfully. Professor Higham said: "We were surprised when the radiocarbon dating produced this very early age. We had suspected that the bones may have been more recent than this, perhaps from the third or fourth centuries. However, the result from the metacarpal hand bone is clearly consistent with someone who lived in the early first century AD. Whether that person is John the Baptist is a question that we cannot yet definitely answer and probably never will." Former Oxford student Dr Hannes Schroeder and Professor Eske Willerslev, both from the University of Copenhagen, also reconstructed the complete mitochondrial DNA genome sequence from three of the human bones to establish that the bones were all from the same individual. Significantly, they identified a family group of genes (mtDNA haplotype) as being a group most commonly found in the Near East, which is better known as the Middle East today -- the region where John the Baptist would have originated from. They also established that the bones were probably of a male individual after an analysis of the nuclear DNA from samples. Dr Schroeder said: "Our worry was that the remains might have been contaminated with modern DNA. However, the DNA we found in the samples showed damage patterns that are characteristic of ancient DNA, which gave us confidence in the results. Further, it seems somewhat unlikely that all three samples would yield the same sequence considering that they had probably been handled by different people. Both of these facts suggest that the DNA we sequenced was actually authentic. Of course, this does not prove that these were the remains of John the Baptist but nor does it refute that theory as the sequences we got fit with a Near Eastern origin." The Bulgarian archaeologists, who excavated the bones, also found a small tuff box (made of hardened volcanic ash) close to the sarcophagus. The tuff box bears inscriptions in ancient Greek that directly mention John the Baptist and his feast day, and text asking God to 'help your servant Thomas'. One theory is that the person referred to as Thomas had been given the task of bringing the relics to the island. An analysis of the box has shown that the tuff box has a high waterproof quality and is likely to have originated from Cappadocia, a region of modern-day Turkey. The Bulgarian researchers believe that the bones probably came to Bulgaria via Antioch, an ancient Turkish city, where the right hand of St John was kept until the tenth century. In a separate study, another Oxford researcher Dr Georges Kazan has used historical documents to show that in the latter part of the fourth century, monks had taken relics of John the Baptist out of Jerusalem and these included portions of skull. These relics were soon summoned to Constantinople by the Roman Emperor who built a church to house them there. Further research by Dr Kazan suggests that the reliquary used to contain them may have resembled the sarcophagus-shaped casket discovered at Sveti Ivan. Archaeological and written records suggest that these reliquaries were first developed and used at Constantinople by the city's ruling elite at around the time that the relics of John the Baptist are said to have arrived there. Dr Kazan said: "My research suggests that during the fifth or early sixth century, the monastery of Sveti Ivan may well have received a significant portion of St John the Baptist's relics, as well as a prestige reliquary in the shape of a sarcophagus, from a member of Constantinople's elite. This gift could have been to dedicate or rededicate the church and the monastery to St John, which the patron or patrons may have supported financially." The scientific analysis of the relics undertaken by Tom Higham and Christopher Ramsey at Oxford, and their colleagues in Copenhagen was supported by the National Geographic Society. The documentary 'Head of John the Baptist', featuring the scientists' work was shown on the National Geographic Channel on 17 June 2012.
1 Nov

Extremely Thin Perfect Nanotube Could Be Grown One Meter Long

At the right temperature, with the right catalyst, there's no reason a perfect single-walled carbon nanotube 1/50,000th the thickness of a human hair can't be grown a meter long. That calculation is one result of a study by collaborators at Rice, Hong Kong Polytechnic and Tsinghua universities who explored the self-healing mechanism that could make such extraordinary growth possible. That's important to scientists who see high-quality carbon nanotubes as critical to advanced materials and, if they can be woven into long cables, power distribution over the grid of the future. The report published online by Physical Review Letters is by Rice theoretical physicist Boris Yakobson; Feng Ding, an adjunct assistant professor at Rice and an assistant professor at Hong Kong Polytechnic; lead author Qinghong Yuan, a postdoctoral researcher at Hong Kong Polytechnic; and Zhiping Xu, a professor of engineering mechanics at Tsinghua and former postdoctoral researcher at Rice. They determined that iron is the best and quickest among common catalysts at healing topological defects -- rings with too many or too few atoms -- that inevitably bubble up during the formation of nanotubes and affect their valuable electronic and physical properties. The right combination of factors, primarily temperature, leads to kinetic healing in which carbon atoms gone astray are redirected to form the energetically favorable hexagons that make up nanotubes and their flat cousin, graphene. The team employed density functional theory to analyze the energies necessary for the transformation. "It is surprising that the healing of all potential defects -- pentagons, heptagons and their pairs -- during carbon nanotube growth is quite easy," said Ding, who was a research scientist in Yakobson's Rice lab from 2005 to 2009. "Only less than one-10 billionth may survive an optimum condition of growth. The rate of defect healing is amazing. If we take hexagons as good guys and others as bad guys, there would be only one bad guy on Earth." The energies associated with each carbon atom determine how it finds its place in the chicken-wire-like form of a nanotube, said Yakobson, Rice's Karl F. Hasselmann Chair in Engineering and a professor of materials science and mechanical engineering and of chemistry. But there has been a long debate among scientists over what actually happens at the interface between the catalyst and a growing tube. "There have been two hypotheses," Yakobson said. "A popular one was that defects are being created quite frequently and get into the wall of the tube, but then later they anneal. There's some kind of fixing process. Another hypothesis is that they basically don't form at all, which sounds quite unreasonable. "This was all just talk; there was no quantitative analysis. And that's where this work makes an important contribution. It evaluates quantitatively, based on state-of-the-art computations, specifically how fast this annealing can take place, depending on location," he said. A nanotube grows in a furnace as carbon atoms are added, one by one, at the catalyst. It's like building the peak of a skyscraper first and adding bricks to the bottom. But because those bricks are being added at a furious rate -- millions in a matter of minutes -- mistakes can happen, altering the structure. In theory, if one ring has five or seven atoms instead of six, it would skew the way all subsequent atoms in the chain orient themselves; an isolated pentagon would turn the nanotube into a cone, and a heptagon would turn it into a horn, Yakobson said. But calculations also showed such isolated defects cannot exist in a nanotube wall; they would always appear in 5/7 pairs. That makes a quick fix easier: If one atom can be prompted to move from the heptagon to the pentagon, both rings come up sixes. The researchers found that very transition happens best when carbon nanotubes are grown at temperatures around 930 kelvins (1,214 degrees Fahrenheit). That is the optimum for healing with an iron catalyst, which the researchers found has the lowest energy barrier and reaction energy among the three common catalysts considered, including nickel and cobalt. Once a 5/7 forms at the interface between the catalyst and the growing nanotube, healing must happen very quickly. The further new atoms push the defect into the nanotube wall, the less likely it is to be healed, they determined; more than four atoms away from the catalyst, the defect is locked in. Tight control of the conditions under which nanotubes grow can help them self-correct on the fly. Errors in atom placement are caught and fixed in a fraction of a millisecond, before they become part of the nanotube wall. The researchers also determined through simulations that the slower the growth, the longer a perfect nanotube could be. A nanotube growing about 1 micrometer a second at 700 kelvins could potentially reach the meter milestone, they found. The work at Rice University was initially supported by the National Science Foundation and at a later stage by an Office of Naval Research grant.
1 Nov

Mars Weather Report: Size of Particles in Martian Clouds of Carbon Dioxide Snow Calculated

In the dead of a Martian winter, clouds of snow blanket the Red Planet's poles -- but unlike our water-based snow, the particles on Mars are frozen crystals of carbon dioxide. Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold -- cold enough to freeze alcohol -- that the gas condenses, forming tiny particles of snow. Now researchers at MIT have calculated the size of snow particles in clouds at both Martian poles from data gathered by orbiting spacecraft. From their calculations, the group found snow particles in the south are slightly smaller than snow in the north -- but particles at both poles are about the size of a red blood cell. "These are very fine particles, not big flakes," says Kerri Cahoy, the Boeing Career Development Assistant Professor of Aeronautics and Astronautics at MIT. If the carbon dioxide particles were eventually to fall and settle on the Martian surface, "you would probably see it as a fog, because they're so small." Cahoy and graduate student Renyu Hu worked with Maria Zuber, the E.A. Griswold Professor of Geophysics at MIT, to analyze vast libraries of data gathered from instruments onboard the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO). From the data, they determined the size of carbon dioxide snow particles in clouds, using measurements of the maximum buildup of surface snow at both poles. The buildup is about 50 percent larger at Mars' south pole than its north pole. Over the course of a Martian year (a protracted 687 days, versus Earth's 365), the researchers observed that as it gets colder and darker from fall to winter, snow clouds expand from the planet's poles toward its equator. The snow reaches halfway to the equator before shrinking back toward the poles as winter turns to spring, much like on Earth. "For the first time, using only spacecraft data, we really revealed this phenomenon on Mars," says Hu, lead author of a paper published in the Journal of Geophysical Research, which details the group's results. Diving through data To get an accurate picture of carbon dioxide condensation on Mars, Hu analyzed an immense amount of data, including temperature and pressure profiles taken by the MRO every 30 seconds over the course of five Martian years (more than nine years on Earth). The researchers looked through the data to see where and when conditions would allow carbon dioxide cloud particles to form. The team also sifted through measurements from the MGS' laser altimeter, which measured the topography of the planet by sending laser pulses to the surface, then timing how long it took for the beams to bounce back. Every once in a while, the instrument picked up a strange signal when the beam bounced back faster than anticipated, reflecting off an anomalously high point above the planet's surface. Scientists figured these laser beams had encountered clouds in the atmosphere. Hu analyzed these cloud returns, looking for additional evidence to confirm carbon dioxide condensation. He looked at every case where a cloud was detected, then tried to match the laser altimeter data with concurrent data on local temperature and pressure. In 11 instances, the laser altimeter detected clouds when temperature and pressure conditions were ripe for carbon dioxide to condense. Hu then analyzed the opacity of each cloud -- the amount of light reflected -- and through calculations, determined the density of carbon dioxide in each cloud. To estimate the total mass of carbon dioxide snow deposited at both poles, Hu used earlier measurements of seasonal variations in the Martian gravitational field done by Zuber's group: As snow piles up at Mars' poles each winter, the planet's gravitational field changes by a tiny amount. By analyzing the gravitational difference through the seasons, the researchers determined the total mass of snow at the north and south poles. Using the total mass, Hu figured out the number of snow particles in a given volume of snow cover, and from that, determined the size of the particles. In the north, molecules of condensed carbon dioxide ranged from 8 to 22 microns, while particles in the south were a smaller 4 to 13 microns. "It's neat to think that we've had spacecraft on or around Mars for over 10 years, and we have all these great datasets," Cahoy says. "If you put different pieces of them together, you can learn something new just from the data." What can the size of snow tell us? Hu says knowing the size of carbon dioxide snow cloud particles on Mars may help researchers understand the properties and behavior of dust in the planet's atmosphere. For snow to form, carbon dioxide requires something around which to condense -- for instance, a small silicate or dust particle. "What kinds of dust do you need to have this kind of condensation?" Hu asks. "Do you need tiny dust particles? Do you need a water coating around that dust to facilitate cloud formation?" Just as snow on Earth affects the way heat is distributed around the planet, Hu says snow particles on Mars may have a similar effect, reflecting sunlight in various ways, depending on the size of each particle. "They could be completely different in their contribution to the energy budget of the planet," Hu says. "These datasets could be used to study many problems." This research was funded by the Radio Science Gravity investigation of the NASA Mars Reconnaissance Orbiter mission.
1 Nov

Ancient Warming Greened Antarctica, Study Finds

A new university-led study with NASA participation finds ancient Antarctica was much warmer and wetter than previously suspected. The climate was suitable to support substantial vegetation -- including stunted trees -- along the edges of the frozen continent. The team of scientists involved in the study, published online June 17 in Nature Geoscience, was led by Sarah J. Feakins of the University of Southern California in Los Angeles, and included researchers from NASA's Jet Propulsion Laboratory in Pasadena, Calif., and Louisiana State University in Baton Rouge. By examining plant leaf wax remnants in sediment core samples taken from beneath the Ross Ice Shelf, the research team found summer temperatures along the Antarctic coast 15 to 20 million years ago were 20 degrees Fahrenheit (11 degrees Celsius) warmer than today, with temperatures reaching as high as 45 degrees Fahrenheit (7 degrees Celsius). Precipitation levels also were found to be several times higher than today. "The ultimate goal of the study was to better understand what the future of climate change may look like," said Feakins, an assistant professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences. "Just as history has a lot to teach us about the future, so does past climate. This record shows us how much warmer and wetter it can get around the Antarctic ice sheet as the climate system heats up. This is some of the first evidence of just how much warmer it was." Scientists began to suspect that high-latitude temperatures during the middle Miocene epoch were warmer than previously believed when co-author Sophie Warny, assistant professor at LSU, discovered large quantities of pollen and algae in sediment cores taken around Antarctica. Fossils of plant life in Antarctica are difficult to come by because the movement of the massive ice sheets covering the landmass grinds and scrapes away the evidence. "Marine sediment cores are ideal to look for clues of past vegetation, as the fossils deposited are protected from ice sheet advances, but these are technically very difficult to acquire in the Antarctic and require international collaboration," said Warny. Tipped off by the tiny pollen samples, Feakins opted to look at the remnants of leaf wax taken from sediment cores for clues. Leaf wax acts as a record of climate change by documenting the hydrogen isotope ratios of the water the plant took up while it was alive. "Ice cores can only go back about one million years," Feakins said. "Sediment cores allow us to go into 'deep time.'" Based upon a model originally developed to analyze hydrogen isotope ratios in atmospheric water vapor data from NASA's Aura spacecraft, co-author and JPL scientist Jung-Eun Lee created experiments to find out just how much warmer and wetter climate may have been. "When the planet heats up, the biggest changes are seen toward the poles," Lee said. "The southward movement of rain bands associated with a warmer climate in the high-latitude southern hemisphere made the margins of Antarctica less like a polar desert, and more like present-day Iceland." The peak of this Antarctic greening occurred during the middle Miocene period, between 16.4 and 15.7 million years ago. This was well after the age of the dinosaurs, which became extinct 64 million years ago. During the Miocene epoch, mostly modern-looking animals roamed Earth, such as three-toed horses, deer, camel and various species of apes. Modern humans did not appear until 200,000 years ago. Warm conditions during the middle Miocene are thought to be associated with carbon dioxide levels of around 400 to 600 parts per million (ppm). In 2012, carbon dioxide levels have climbed to 393 ppm, the highest they've been in the past several million years. At the current rate of increase, atmospheric carbon dioxide levels are on track to reach middle Miocene levels by the end of this century. High carbon dioxide levels during the middle Miocene epoch have been documented in other studies through multiple lines of evidence, including the number of microscopic pores on the surface of plant leaves and geochemical evidence from soils and marine organisms. While none of these 'proxies' is as reliable as the bubbles of gas trapped in ice cores, they are the best evidence available this far back in time. While scientists do not yet know precisely why carbon dioxide was at these levels during the middle Miocene, high carbon dioxide, together with the global warmth documented from many parts of the world and now also from the Antarctic region, appear to coincide during this period in Earth's history. This research was funded by the U.S. National Science Foundation with additional support from NASA. The California Institute of Technology in Pasadena manages JPL for NASA.
1 Nov

‘Extremely Little’ Telescope Discovers Pair of Odd Planets

Even small telescopes can make big discoveries. Though the KELT North telescope in southern Arizona carries a lens no more powerful than a high-end digital camera, it's just revealed the existence of two very unusual faraway planets. One planet is a massive, puffed-up oddity that could change ideas of how solar systems evolve. The other orbits a very bright star, and will allow astronomers to make detailed measurements of the atmospheres of these bizarre worlds. Ohio State University doctoral student Thomas Beatty and Vanderbilt University research scientist Robert Siverd reported these discoveries for the KELT-North team at the American Astronomical Society national meeting in Anchorage, Alaska. Beatty described the newly discovered planets in a news conference on June 13. One planet is located in the constellation Andromeda. Dubbed KELT-1b, it is so massive that it may better be described as a 'failed star' rather than a planet. A super hot, super dense ball of metallic hydrogen, KELT-1b is located so close to its star that it whips through an entire "yearly" orbit in a little over a day -- all the while being blasted by six thousand times the radiation Earth receives from the sun. What's more, the planet appears to have been jostled in the past by a previously unknown distant binary companion star that is orbiting the KELT-1 solar system. In short, the planet "resets the bar for 'weird,'" said Scott Gaudi, an associate professor of astronomy at Ohio State and a member of the research team. The other planet, KELT-2Ab, is located in the constellation Auriga, and is typical of many previously discovered extrasolar planets in that it much resembles our own Jupiter. But its parent star is very bright -- so bright that astronomers believe that they will be able to directly observe KELT-2Ab's atmosphere by studying the starlight that shines through it and the infrared heat that radiates from it -- using telescopes located not only in space, but also on the ground. "Normally, we would need a space telescope to do all that, but in this case the host star is so bright that we can make many of these measurements from the ground," Beatty said. KELT is short for "Kilodegree Extremely Little Telescope." Astronomers at Ohio State and Vanderbilt University jointly operate KELT North and its twin, KELT South, in order to fill a large gap in the available technologies for finding extrasolar planets. Other telescopes were designed to look at very faint stars in tiny sections of the sky, and at very high resolution, Beatty explained. The KELTs, in contrast, look at millions of very bright stars at once, over broad sections of sky, and at low resolution. "Our stars are so bright, these 'more powerful' telescopes can't even look at them," Beatty said. The KELT team scans those bright stars, and watches to see if the starlight dims just a little -- an indication that a planet has crossed in front of the star. The technique is called the "transit method," and takes advantage of situations such as the recent transit of Venus across the face of the sun in our own solar system. It's a low-cost means of planet-hunting, using mostly off-the-shelf technology; Whereas a traditional astronomical telescope costs millions of dollars to build, the hardware for a KELT telescope runs less than $75,000. Joshua Pepper, a research assistant professor and fellow of the Vanderbilt Initiative in Data-Intensive Astrophysics, built KELT North when he was a doctoral student at Ohio State. Study co-author Robert Siverd further developed and enhanced the instrument before he went to Vanderbilt. There, they work with Keivan Stassun, professor of physics and astronomy, who hired them to build KELT South. "Exoplanets like KELT-1b and KELT-2Ab that pass directly in front of very bright stars are extremely important, but extremely rare, because there just aren't that many very bright stars in the sky," said Stassun. "The KELT-North and KELT-South partnership gives us the advantage of hunting for these rare gems from both hemispheres, doubling the hunting grounds." KELT North covers the northern sky, while KELT South, located near Cape Town, South Africa, covers the southern sky. Both newly discovered planets were found using KELT North. After KELT detected these new astronomical objects, a collaboration of KELT with astronomers at Harvard, Swarthmore, the University of Louisville, Las Cumbres Observatory, and even amateur astronomers helped to confirm the identities of these objects with additional observations. According to Pepper, "The KELT project has benefited from the dedication of a great team of astronomers, and represents an enormous scientific return on a relatively small investment." The more typical of the two planets, KELT-2Ab, is 30 percent larger than Jupiter with 50 percent more mass. It resides in a binary system called HD 42176, with one star that is slightly bigger than our sun, and another star that is slightly smaller. KELT-2Ab orbits the bigger star, which is bright enough to be seen from Earth with binoculars. That's why astronomers hope to be able measure the starlight that passes through KELT-2Ab's atmosphere when the star returns to KELT North's field of view this November. KELT-1b, in contrast, is one of the most bizarre transiting companions ever detected. It orbits a star not unlike our sun, but the similarity to our solar system ends there. The planet is slightly larger than Jupiter, but contains 27 times the mass. Thus, it qualifies as a 'failed star,' or "brown dwarf." Although it is made primarily of hydrogen, it is so massive and compressed that its density matches that of the densest naturally occurring element on Earth: osmium -- a shiny, bluish metal found in platinum ore that is approximately twice as dense as lead. Because it orbits its host star once every 30 hours, a solar "year" on KELT-1b passes in a little more than one Earth day. And because it orbits so closely, it is blasted with 6,000 times the amount of stellar radiation than we are exposed to on Earth. Its surface temperature is likely above 4,000 degrees Fahrenheit (about 2,200 degrees Celsius). By comparison, the planet Mercury orbits our sun once every 88 days, and the hottest temperature on the surface reaches only 800 degrees Fahrenheit (more than 425 degrees Celsius). Likely in response to the intense radiation, KELT-1b has inflated to a larger size than astronomers would normally predict. "This is the first definitively 'inflated' brown dwarf found, and exactly how this happened is a complete mystery that should keep theorists busy for a while," Gaudi said. KELT-1b is a strange world, indeed. If you could stand on the surface, the "sun" would take up one quarter of the sky overhead. Fewer than 1 percent of the extrasolar planets ever discovered have been both extremely massive and extremely close to their host stars. "This is a great system for studying orbital dynamics," said Siverd, who is the lead investigator on the KELT-1 discovery. "It has the strongest tides of any brown dwarf system found so far," he added. KELT-1b and its star are locked in a cosmic dance that resembles that of Earth and the moon, with a notable exception. The moon is tidally locked to Earth -- that's why we always see the same face of the moon. But Earth itself is not tidally locked to the moon. KELT-1b exerts so much gravitational force on its star that the star's rotation rate actually matches the planet's orbit: the two are tidally locked in each other's gaze -- for now. In a few billion years, KELT-1b's star will expand and swallow the planet whole. Gaudi said that astronomers are beginning to suspect that something unusual happens during the evolution of such solar systems that drives massive planets into these kinds of close encounters. The presence of a stellar sibling orbiting both of the newly discovered solar systems may be a "smoking gun" clue that past interactions between the planets and these distant siblings is an important part of that process. "We think they are born at much larger, colder distances," he said, "and then like retirees moving to Florida, they move to warmer climes as they get older." This work was funded by the National Science Foundation, NASA, and Vanderbilt University.
1 Nov

Neutrons Escaping to a Parallel World?

In a paper recently published in European Physical Journal (EPJ) C, researchers hypothesised the existence of mirror particles to explain the anomalous loss of neutrons observed experimentally. The existence of such mirror matter had been suggested in various scientific contexts some time ago, including the search for suitable dark matter candidates. Theoretical physicists Zurab Berezhiani and Fabrizio Nesti from the University of l'Aquila, Italy, reanalysed the experimental data obtained by the research group of Anatoly Serebrov at the Institut Laue-Langevin, France. It showed that the loss rate of very slow free neutrons appeared to depend on the direction and strength of the magnetic field applied. This anomaly could not be explained by known physics. Berezhiani believes it could be interpreted in the light of a hypothetical parallel world consisting of mirror particles. Each neutron would have the ability to transition into its invisible mirror twin, and back, oscillating from one world to the other. The probability of such a transition happening was predicted to be sensitive to the presence of magnetic fields, and could therefore be detected experimentally. This neutron-mirror-neutron oscillation could occur within a timescale of a few seconds, according to the paper. The possibility of such a fast disappearance of neutrons -- much faster than the ten-minute long neutron decay -- albeit surprising, could not be excluded by existing experimental and astrophysical limits. This interpretation is subject to the condition that Earth possesses a mirror magnetic field on the order of 0.1 Gauss. Such a field could be induced by mirror particles floating around in the galaxy as dark matter. Hypothetically, Earth could capture the mirror matter via some feeble interactions between ordinary particles and those from parallel worlds.
1 Nov

Small Planets Don’t Need ‘Heavy Metal’ Stars to Form

The formation of small worlds like Earth previously was thought to occur mostly around stars rich in heavy elements such as iron and silicon. However, new ground-based observations, combined with data collected by NASA's Kepler space telescope, show small planets form around stars with a wide range of heavy element content and suggest they may be widespread in our galaxy. A research team led by Lars A. Buchhave, an astrophysicist at the Niels Bohr Institute and the Centre for Star and Planet Formation at the University of Copenhagen, studied the elemental composition of more than 150 stars harboring 226 planet candidates smaller than Neptune. "I wanted to investigate whether small planets needed a special environment in order to form, like the giant gas planets, which we know preferentially develop in environments with a high content of heavy elements," said Buchhave. "This study shows that small planets do not discriminate and form around stars with a wide range of heavy metal content, including stars with only 25 percent of the sun's metallicity." Astronomers refer to all chemical elements heavier than hydrogen and helium as metals. They define metallicity as the metal content of heavier elements in a star. Stars with a higher fraction of heavy elements than the sun are considered metal-rich. Stars with a lower fraction of heavy elements are considered metal-poor. Planets are created in disks of gas and dust around new stars. Planets like Earth are composed almost entirely of elements such as iron, oxygen, silicon and magnesium. The metallicity of a star mirrors the metal content of the planet-forming disk. Astronomers have hypothesized that large quantities of heavy elements in the disk would lead to more efficient planet formation. It has long been noted that giant planets with short orbital periods tend to be associated with metal-rich stars. Unlike gas giants, the occurrence of smaller planets is not strongly dependent on the heavy element content of their host stars. Planets up to four times the size of Earth can form around stars with a wide range of heavy element content, including stars with a lower metallicity than the sun. The findings are described in a new study published in the journal Nature. "Kepler has identified thousands of planet candidates, making it possible to study big-picture questions like the one posed by Lars. Does nature require special environments to form Earth-size planets?" said Natalie Batalha, Kepler mission scientist at NASA's Ames Research Center at Moffett Field, Calif. "The data suggest that small planets may form around stars with a wide range of metallicities -- that nature is opportunistic and prolific, finding pathways we might otherwise have thought difficult." The ground-based spectroscopic observations for this study were made at the Nordic Optical Telescope on La Palma in the Canary Islands; Fred Lawrence Whipple Observatory on Mt. Hopkins in Arizona; McDonald Observatory at the University of Texas at Austin; and W.M. Keck Observatory atop Mauna Kea in Hawaii. Launched in March 2009, Kepler searches for planets by continuously monitoring more than 150,000 stars, looking for telltale dips in their brightness caused by passing, or transiting, planets. At least three transits are required to verify a signal as a planet. Follow-up observations from ground-based telescopes are also needed to confirm a candidate as a planet. Ames manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed the Kepler mission development. JPL is managed by the California Institute of Technology, also in Pasadena, for NASA. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.
1 Nov

Scientists See New Hope for Restoring Vision With Stem Cell Help

Human-derived stem cells can spontaneously form the tissue that develops into the part of the eye that allows us to see, according to a study published by Cell Press in the 5th anniversary issue of the journal Cell Stem Cell. Transplantation of this 3D tissue in the future could help patients with visual impairments see clearly. "This is an important milestone for a new generation of regenerative medicine," says senior study author Yoshiki Sasai of the RIKEN Center for Developmental Biology. "Our approach opens a new avenue to the use of human stem cell-derived complex tissues for therapy, as well as for other medical studies related to pathogenesis and drug discovery." During development, light-sensitive tissue lining the back of the eye, called the retina, forms from a structure known as the optic cup. In the new study, this structure spontaneously emerged from human embryonic stem cells (hESCs) -- cells derived from human embryos that are capable of developing into a variety of tissues -- thanks to the cell culture methods optimized by Sasai and his team. The hESC-derived cells formed the correct 3D shape and the two layers of the optic cup, including a layer containing a large number of light-responsive cells called photoreceptors. Because retinal degeneration primarily results from damage to these cells, the hESC-derived tissue could be ideal transplantation material. Beyond the clinical implications, the study will likely accelerate the acquisition of knowledge in the field of developmental biology. For instance, the hESC-derived optic cup is much larger than the optic cup that Sasai and collaborators previously derived from mouse embryonic stem cells, suggesting that these cells contain innate species-specific instructions for building this eye structure. "This study opens the door to understanding human-specific aspects of eye development that researchers were not able to investigate before," Sasai says. The anniversary issue containing Sasai's study will be given to each delegate attending the 2012 ISSCR meeting in Yokohama, Japan. To highlight the ISSCR meeting and showcase the strong advances made by Japanese scientists in the stem cell field, the issue will also feature two other papers from Japanese authors, including the research groups of Akira Onishi and Jun Yamashita. In addition, the issue contains a series of reviews and perspectives from worldwide leaders in stem cell research.
 
1 Nov

Uranium-Series Dating Reveals Iberian Paintings Are Europe’s Oldest Cave Art

Paleolithic paintings in El Castillo cave in Northern Spain date back at least 40,800 years -- making them Europe's oldest known cave art, according to new research published June 14 in Science. The research team was led by the University of Bristol and included Dr Paul Pettitt from the University of Sheffield's Department of Archaeology, a renowned expert in cave art. Their work found that the practice of cave art in Europe began up to 10,000 years earlier than previously thought, indicating the paintings were created either by the first anatomically modern humans in Europe or, perhaps, by Neanderthals. A total of 50 paintings in 11 caves in Northern Spain, including the UNESCO World Heritage sites of Altamira, El Castillo and Tito Bustillo, were dated by a team of UK, Spanish and Portuguese researchers led by Dr Alistair Pike of the University of Bristol, UK. As traditional methods such as radiocarbon dating do not work where there is no organic pigment, the team dated the formation of tiny stalactites on top of the paintings using the radioactive decay of uranium. This gave a minimum age for the art. Where larger stalagmites had been painted, maximum ages were also obtained. Hand stencils and disks made by blowing paint onto the wall in El Castillo cave were found to date back to at least 40,800 years, making them the oldest known cave art in Europe, 5-10,000 years older than previous examples from France. A large club-shaped symbol in the famous polychrome chamber at Altamira was found to be at least 35,600 years old, indicating that painting started there 10,000 years earlier than previously thought, and that the cave was revisited and painted a number of times over a period spanning more than 20,000 years. Dr Pike said: "Evidence for modern humans in Northern Spain dates back to 41,500 years ago, and before them were Neanderthals. Our results show that either modern humans arrived with painting already part of their cultural activity or it developed very shortly after, perhaps in response to competition with Neanderthals -- or perhaps the art is Neanderthal art." The creation of art by humans is considered an important marker for the evolution of modern cognition and symbolic behaviour, and may be associated with the development of language. Dr Pike said: "We see evidence for earlier human symbolism in the form of perforated beads, engraved egg shells and pigments in Africa 70-100,000 years ago, but it appears that the earliest cave paintings are in Europe. One argument for its development here is that competition for resources with Neanderthals provoked increased cultural innovation from the earliest groups of modern humans in order to survive. Alternatively, cave painting started before the arrival of modern humans, and was done by Neanderthals. That would be a fantastic find as it would mean the hand stencils on the walls of the caves are outlines of Neanderthals' hands, but we will need to date more examples to see if this is the case." The findings are particularly significant because cave art has always been difficult to date accurately. Dr Pike said: "Engravings and, in many cases, paintings lack organic pigments or binders suitable for radiocarbon dating. Where suitable material -- such as charcoal pigments -- does exist, only small samples can be dated to minimize damage to the art. This magnifies the effects of contamination and produces less accurate results. "Instead, we measured uranium isotopes in the thin calcite flowstone growths that formed on the surfaces of the paintings and engravings to date the art. This technique, known as uranium-series disequilibrium, is used extensively in Earth Sciences and avoids the problems related to radiocarbon dating." Dr Pettitt said: "Until now our understanding of the age of cave art was sketchy at best; now we have firmly extended the earliest age of European cave art back by several thousand years, to the time of the last Neanderthals and earliest Homo sapiens. These earliest images do not represent animals, and suggest that the earliest art was non-figurative, which may have significant implications for how art evolved." Team member and dating expert Dr Dirk Hoffmann of the National Centre for the Investigation of Human Evolution (CENIEH) in Burgos, Spain said: "The key development was our method to date tiny calcium carbonate deposits similar to stalactites. We can now date samples of just 10 milligrams -- about as small as a grain of rice. This has allowed us to find samples that had formed directly on top of hundreds of paintings, whereas the larger stalactites were much less frequent."
1 Nov

Grasshoppers Frightened by Spiders Affect Whole Ecosystem

Hebrew University, Yale researchers show how grasshoppers 'stressed' by spiders affect the productivity of our soil. How do grasshoppers who are being frightened by spiders affect our ecosystem? In no small measure, say researchers at the Hebrew University of Jerusalem and at Yale University in the US. A grasshopper who is in fear of an attacker, such as a spider, will enter a situation of stress and will consume a greater quantity of carbohydrate-rich plants -- similar to humans under stress who might eat more sweets. This type of reaction will, in turn, cause chemical changes in the grasshopper and in its excretions, affecting the ecosystem it inhabits. How does this happen? When the scared grasshopper dies, its carcass, now containing less nitrogen as a result of its diet change, will have an effect on the microbes in the ground, which are responsible for breaking down animals and plants. With less nitrogen available, the microbes will be decomposing the hard-to-break-down plant materials in the soil at a slower rate. Thus, the fear of predation may slow down degradation of complex organic materials to the simpler compounds required for plant growth. Research on this biological-ecological phenomenon was carried out by Dr. Dror Halwena of the Department of Ecology, Evolution and Behavior at the Alexander Silberman Institute of Life Sciences at the Hebrew University of Jerusalem, in cooperation with researchers at Yale University in the United States. An article on their research appears in the current edition of the journal Science. In their research, the scientists exposed grasshoppers to spiders in order to arouse the stress reaction. They also used a control group of non-stressed grasshoppers. The scared grasshoppers had a higher carbon-to-nitrogen ratio in their bodies than non-scared grasshoppers. In further laboratory and field tests, the researchers tested the influence of remains of grasshoppers from the two groups on soil. After the microbes consumed the grasshopper remains, the researchers added plants to the surface. In the experiments, it was shown that the decomposition rate of the plants in the areas in which the stress-free grasshopper remains were introduced decomposed at a rate between 62 and 200 percent faster than in the samples in which the stressed grasshopper s were put. In a further experiment, the researchers used "artificial grasshoppers" -- a mixture of sugar, protein, and chitin (the organic compound found in the grasshopper external skeleton) -- in varying quantities. Here, too, they found that even a small amount of nitrogen (found in the protein) added to the soil increases significantly the functioning of the microbes responsible for breaking down the organic matter in plants. "We are dealing here with an absolutely new kind of mechanism whereby every small chemical change in a creature can regulate the natural cycle, thus in effect affecting the ecology in total, such as the amount of carbon dioxide released into the atmosphere (through decomposition) and field crop productivity. This has tremendous consequences for our ecological understanding of the living world," said Dr. Halwena. "We are gaining a greater understanding of the necessity of conserving all of the component parts of the ecosystem in general and of predators in particular. We are losing predators in nature at a much faster rate than other species," Dr. Halwena commented. He also viewed the research as a vehicle that will enable scientists to better predict changes in the biological system as a result of such human-induced phenomenon as overfishing, hunting or global warming that can undermine the entire ecosystem.