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7/31/2012
A new study, supported in part by the NASA Astrobiology Institute, suggests that meteorites and their parent asteroids are the most-likely sources of water on Earth. The research led by the Carnegie Institution for Science's Conel Alexander indicates that these rocks from space were the sources of early Earth’s volatile elements -- which include hydrogen, nitrogen, and carbon -- and possibly organic material. Understanding if and how volatile elements were delivered to the early Earth is important in determining the origins of both water and life on our planet. This work was partially funded by NASA Cosmochemistry, the NASA Astrobiology Institute, Carnegie Institution of Canada, the Natural Sciences and Engineering Research Council of Canada, the W.M. Keck Foundation, and the UK Cosmochemical Analysis Network. |
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7/31/2012
Scientists at Syracuse University - part of NAI's team at RPI - report new information about the history of water on Mars in the current issue of Planetary and Space Science. Focused on the hematite spherules known as the "blueberries" discovered by NASA's Mars Exploration Rover Opportunity in 2004, the study suggests that ages measured using the relative abundances of uranium, thorium, and helium in the blueberries could yield the time that has passed since water last wetted the sediments. |
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7/31/2012
Using combined data from a trio of orbiting X-ray telescopes, including NASA's Chandra X-ray Observatory and the Japan-led Suzaku satellite, astronomers have obtained a rare glimpse of the powerful phenomena that accompany a still-forming star. A new study based on these observations indicates that intense magnetic fields drive torrents of gas into the stellar surface, where they heat large areas to millions of degrees. X-rays emitted by these hot spots betray the newborn star's rapid rotation.
For more, including an animation of these X-ray hot spots, read the press release from NASA's Goddard Space Flight Center. |
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7/31/2012
A team of Penn State University astronomers has obtained very precise measurements of a pair of stars that are orbited by a planet – like the binary system of the fictional planet Tatooine from the movie Star Wars. The orbits of the stars and planet in the system, named Kepler-16, are aligned so that they eclipse or transit each other when observed from Earth. The new measurements will aid astronomers in understanding how stars and planetary systems form. The data was obtained with the Hobby-Eberly Telescope at McDonald Observatory and provides an important independent test of a new technique for measuring masses from Kepler spacecraft data.
A preprint of the paper is online at http://arxiv.org/abs/1205.0259. Funding for this research was provided by the Center for Exoplanets and Habitable Worlds, the NASA Astrobiology Institute, the Penn State Astrobiology Research Center, and the National Science Foundation. |
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7/31/2012
With support from the NASA Astrobiology Program, researchers at the Massachusetts Institute of Technology (MIT) have discovered a new bacterial gene that could provide clues about how life survives in some of Earth’s most extreme environments.
The gene codes for a protein, named HpnR, that is responsible for producing bacterial lipids known as 3-methylhopanoids. These lipids could help prepare nutrient-starved microbes to make a sudden appearance in nature when conditions are favorable. It allows the organisms to survive in extreme, oxygen-depleted environments until food — such as methane and the oxygen needed to metabolize it — become available.
The lipid produced by the HpnR protein may also be used as a biomarker in rock layers to identify dramatic changes in oxygen levels throughout Earth’s history.
"The thing that interests us is that this could be a window into the geologic past," says MIT postdoc Paula Welander, who led the research. "In the geologic record, many millions of years ago, we see a number of mass extinction events where there is also evidence of oxygen depletion in the ocean. It's at these key events, and immediately afterward, where we also see increases in all these biomarkers as well as indicators of climate disturbance. It seems to be part of a syndrome of warming, ocean deoxygenation and biotic extinction. The ultimate causes are unknown."
The research was supported by the NASA Astrobiology Program via the NASA Postdoctoral Program, and was completed under the guidance of NASA Astrobiology Institute Principle Investigator, Roger Summons, at the Massachusetts Institute of Technology (MIT).
The paper, “Discovery, taxonomic distribution, and phenotypic characterization of a gene required for 3-methylhopanoid production,” was published on July 23, 2012, in the Proceedings of the National Academy of Science (PNAS) under lead author Paula V. Welander.
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5/31/2012
 The shape of an RNA molecule remains the same with either magnesium (Mg) or iron (Fe).
When life began on Earth, iron may have done the job of magnesium, making life possible.
On the periodic table of the elements, iron and magnesium are far apart. But new evidence discovered by NAI’s team at the Georgia Institute of Technology suggests that three billion years ago, iron did the job magnesium does today in helping Ribonucleic acid (RNA), a molecule essential for life, assume the molecular shapes necessary for biology.
The results of the study were published online on May 31, 2012 in the journal PLoS ONE.
There is considerable evidence that the evolution of life passed through an early stage when RNA played a more central role, doing the jobs of DNA and protein before they appeared. During that time, more than three billion years ago, the environment lacked oxygen but had lots of available iron.
”One of the greatest challenges in astrobiology is understanding how life began on Earth billions of years ago when the environment was very different than it is today,” said Carl Pilcher, director of the Astrobiology Institute at NASA’s Ames Research Center, Moffett Field, Calif. “This study shows us how conditions on early Earth may have been conducive to the development of life.”
In the new study, researchers from the Georgia Institute of Technology, Atlanta, used experiments and numerical calculations to show that under early Earth conditions, with little oxygen around, iron can substitute for magnesium in RNA, enabling it to assume the shapes it needs to catalyze life’s chemical reactions. In fact, it catalyzed those reactions better with iron than with magnesium.
“The primary motivation of this work was to understand RNA under plausible early Earth conditions.” said Loren Williams, a professor in the School of Chemistry and Biochemistry at Georgia Tech and leader of the NAI team. “Our hypothesis is that RNA evolved in the presence of iron and is optimized to work with iron.”
Free oxygen gas was almost nonexistent more than three billion years ago in early Earth’s atmosphere. When oxygen began entering the environment as a product of photosynthesis, it turned Earth’s available iron to rust, forming massive banded iron deposits that are still mined today. When all that iron got tied up in those deposits, it was no longer available. The current study indicates that RNA then began using magnesium, resulting in life as we know it today.
In future studies, the researchers plan to investigate what unique functions RNA can perform with iron that are not possible with magnesium.
In addition to Williams, Georgia Tech School of Biology postdoctoral fellow Shreyas Athavale, research scientist Anton Petrov, and professors Roger Wartell and Stephen Harvey, and Georgia Tech School of Chemistry and Biochemistry postdoctoral fellow Chiaolong Hsiao and professor Nicholas Hud also contributed to this research. |
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4/3/2012
 Still shot from an animation to demonstrate a particle bouncing around different regions of the nebula and seeing different fluxes of photons. Animation credit: Fred Ciesla
Complex organic compounds, including many important to life on Earth, were readily produced under conditions that likely prevailed in the primordial solar system. Scott Sandford of NAI's NASA Ames Research Center Team and his colleague Fred Ciesla at the University of Chicago came to this conclusion after linking computer simulations to laboratory experiments. Their study appears in Science Express |
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3/21/2012
 David Johnston, Assistant Professor of Earth and Planetary Sciences at Harvard University.
For more than a decade, scientists have dismissed claims that examining carbon-rich rocks could yield clues to the atmospheric and oceanic conditions on Earth hundreds of millions of years ago. Now, however, researchers including members of NAI's MIT Team are challenging that belief, and suggesting that data gleaned from the rocks sheds light on how changes in the atmosphere and oceans helped set the stage for the emergence of animal life.
In one of the largest studies of its kind, described in the March 14 issue of Nature, a group of researchers led by David Johnston, Assistant Professor of Earth and Planetary Sciences, analyzed hundreds of samples of carbon-rich rock collected from sites in Canada, Mongolia, and Namibia. Their findings show that carbon isotope records from the mid-Neoproterozoic era — between 717 million and 635 million years ago — can be “read” as a faithful snapshot of the surface carbon cycle. |
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3/19/2012
 A meteorite analyzed in the study at its collection site in Antarctica. Credit: Antarctic Search for Meteorites program, Case Western Reserve University
Creating some of life’s building blocks in space may be a bit like making a sandwich – you can make them cold or hot. This evidence that there is more than one way to make crucial components of life increases the likelihood that life emerged elsewhere in the Universe, according to the research team led by astrobiologists at NAI’s Goddard Center for Astrobiology. It also gives support to the theory that a “kit” of ready-made parts created in space and delivered to Earth by impacts from meteorites and comets assisted the origin of life.
In a recent study published in Meteoritics and Planetary Science, scientists from NAI's Goddard Space Flight Center Team analyzed samples from fourteen carbon-rich meteorites with minerals that indicated they had experienced high temperatures – in some cases, over 2,000 degrees Fahrenheit. They found amino acids, which are the building blocks of proteins, used by life to speed up chemical reactions and build structures like hair, skin, and nails. |
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3/19/2012
 Titan's hazy atmosphere. Credit: NASA/JPL/Space Science Institute
About two and a half billion years ago, Earth might have been confused for Titan. New research suggests that our planet had the same hazy, methane-rich atmosphere as Saturn’s largest moon, Titan.
For the first third of the history of life on Earth, the atmosphere was devoid of the oxygen we breathe, supporting a dramatically different chemistry. A new study from a group including memembers of NAI's Virtual Planetary Laboratory Team suggests connections between Earth’s atmosphere and its biosphere that induced an orange, hydrocarbon haze that would have blocked incoming sunlight and cooled the planet.
The study, published in Nature Geoscience, provides analyses of 2.5 billion year old rock cores from South Africa that reveal a series of unique chemical signatures of atmospheric change. When these data are plugged into atmospheric models, it is revealed that early Earth oscillated between two atmospheric states: one with a thin, orange haze and the other without any haze.
The trigger for these events appears to be atmospheric changes in a potent greenhouse gas, methane. These high concentrations of methane, produced by biological activity, caused the haze and an “anti-greenhouse” effect. This is one of the earliest examples of the tight climatic coupling between Earth and its inhabitants. |
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3/7/2012
 Geological background of the samples analyzed in this study. Panel A shows the geological map at Marble Bar and the location of the ABDP-1 drill core. Panel B shows the simplified stratigraphic column of the lower part of the Pilbara Supergroup, with ages constrained by zircon U–Pb geochronology.
Astrobiologists from NAI’s team at the University of Wisconsin, Madison have recently published a study of drill cores obtained through the NAI-funded Archean Biosphere Drilling Project which sampled the 3.4 billion year old Apex Basalt from the Pilbara Craton in Western Australia. Their innovative approach directly dates oxidation products of the ancient rock, and they show that oxidation occurred in the Phanerozoic during deep weathering. Their results indicate that oxidation of the Apex Basalt did not occur in the Archean, and therefore cannot be used to infer an oxygenated atmosphere at that time. Their paper appears in Earth and Planetary Science Letters. |
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2/20/2012
 An example of the mineral montmorillonite (Pen for scale). This sample comes from the mineral collection of Brigham Young University Department of Geology, Provo, Utah. Photograph by Andrew Silver.
One popular hypothesis for the origin of life suggests that the nucleic acid, RNA, performed two important roles: RNA stored genetic information and also catalyzed the chemical reactions that helped get life started. A hurdle in this route to life is that we don’t know how the first RNA molecules themselves were formed. A new study supported by the NASA Astrobiology Institute and led by James Ferris of NAI's New York Center for Astrobiology at Rensselaer Polytechnic Institute Team may further our understanding of the ‘RNA world’ hypothesis.
RNA molecules are built from smaller pieces (a.k.a. monomers). When pieced together to form RNA, these monomers must be ‘activated’ – in other words, they need to be switched ‘on’ and chemically ready to react with other molecules. This produces a strand of RNA that could be useful in the RNA world scenario.
A new study is shedding light on this step in the process. The research focuses on montmorillonite – a group of soft minerals that are usually found in the form of clay and occur naturally on Earth. Previous work has shown that activated nucleic acids can be formed when montmorillonite minerals are present to catalyze the reaction. However, not all montmorillonites are catalytic – and the new research is helping us understand why. The extent of catalysis depends on the magnitude of the negative charge between layers of montmorillonite minerals, the number of negatively charged ions that produce this charge, and also the pH at which the reaction occurs.
The study also reveals new characteristics of the RNA molecules formed by montmorillonite catalysis, and is beginning to unravel the mechanism by which montmorillonite helps RNA form.
Scientists are not sure if montmorillonite or nucleic acids were present on the early Earth, but it is possible. Additionally, the recent discovery of montmorillonite on Mars raises questions about whether or not a similar process could have occurred on the red planet.
The study, “The role of montmorillonite in its catalysis of RNA synthesis” was published in the journal Applied Clay Science under lead author Michael F. Aldersley and coauthors Prakash Joshi, Jonathan Price and James Ferris. |
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2/16/2012
 This artist's concept shows what a fiery hot star and its planetary companion might look like close up in infrared. Credit: NASA/JPL
A team of researchers including members of NAI's Virtual Planetory Laboratory Team have examined the potential of detecting oceans on terrestrial-sized exoplanets by using observations in the near-infrared (NIR). Previously, it had been suggested that oceans on distant, rocky worlds could be identified by observing variabilities in scattered light. However, the team suggests that such observations could be difficult due to atmospheric scattering. On Earth, this scattering is reduced at certain wavelengths in the NIR.
Based on scattering in Earth’s atmosphere, the team modeled two wavebands of light in the NIR that could be useful in the hunt for extrasolar oceans. The team confirmed that observations at NIR wavelengths are better for detecting oceans than those at visible wavelengths – but only when aerosols in the planet’s atmosphere are thin and cloud cover is minimal. Ultimately, the team concluded that observing Earth-like worlds in the NIR could help detect water vapor and other atmospheric constituents that absorb light.
The paper, “Searching for Water Earths in the Near-Infrared” was published in the Astrophysical Journal. |
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2/10/2012
 The EXPOSE-R test container installed on the outside of the International Space Station (ISS). Credit: NASA
In March of 2009, the ORGANIC experiment was integrated into the European EXPOSE-R facility on the International Space Station (ISS). EXPOSE-R contained experiments dedicated to Astrobiology, and was mounted externally on the ISS where the organic samples it contained were exposed to the space environment for 97 days. The samples, including those of the ORGANIC experiment, were then returned to Earth in the spring of 2011. During the 22 months outside the ISS, ORGANIC samples were exposed to direct solar irradiation of more than 2500 hours, exceeding the limits of laboratory simulations.
The 14 samples in the ORGANIC experiment package included compounds known as Polycyclic Aromatic Hydrocarbons (PAHs) and fullerenes. PAHs are present in many space environments, including external galaxies, and in solar system materials like meteorites and possibly comets. Fullerenes have been identified in young planetary nebula. These compounds are among the most abundant organic materials in space, and could have played a role in the origins of life on the early Earth. Studying the stability of these molecules can help astrobiologists understand the evolution and degradation of large carbon-containing molecules in space environments.
Researchers, including members of NAI's University of Wisconsin Team, recently published a discussion of the experiment package and the anticipated results upon its return from the ISS in the journal Advances in Space Research. |
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2/8/2012
A team of researchers from NAI's Montana State University Team has proposed a new path in the evolution of biological nitrogen fixation on Earth. Nitrogen is one of the most important elements for life on Earth, and astrobiologists have long been interested in its role in the history and evolution of life.
Nitrogen is abundant on our planet as an atmospheric gas. However, in order for Nitrogen to be accessible for life, it must be converted into other chemical forms. A key step in the global cycling of nitrogen is biological nitrogen fixation, which is accomplished via a protein known as ‘nitrogenase.’ Three forms of nitrogenase are known – all similar, but containing slightly different metallic complexes. Previously, scientists thought the most common nitrogenase found today (which contains the element molybdenum (Mo)) appeared later in life’s evolution that the two lesser-found forms (containing vanadium (V) or iron(Fe)). The new study has revealed an evolutionary path that places Mo-dependent nitrogenase earlier than the V and Fe forms. The study is changing views of how this important biological pathway evolved through time – shedding light on the early history of life on Earth.
The study was published in the journal Frontiers in Microbiology under lead author Eric S. Boyd. The research was carried out as part of the NAI project "Evolution of Nitrogen Fixation, Photosynthesis, Hydrogen Metabolism, and Methanogenesis." |
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12/8/2011
 Panorama of Russia's Imandra/Varzuga Greenstone Belt where FAR DEEP drilling took place. Credit: Victor Melezhik, Geological Survey of Norway/University of Bergen
Based on studies of rock cores, a team of geoscientists that include members of NAI's Penn State Team have determined that oxygen did not appear in Earth’s atmosphere in a single event. Instead, atmospheric oxygen came about in a long series of starts and stops.
The research was conducted using samples collected in the summer of 2007 during the Fennoscandia Arctic Russia – Drilling Early Earth Project (FAR DEEP). Scientists drilled a series of shallow, two-inch diameter cores and overlapped them to create a record of the Proterozoic Eon—2,500 million to 542 million years ago.
“We’ve always thought that oxygen came into the atmosphere really quickly during an event,” said Lee Kump, a geoscientist at Penn State University. “We are no longer looking for an event. Now we’re looking for when and why oxygen became a stable part of the Earth’s atmosphere.”
The research was published in the December 1, 2011 issue of Science Express under lead author Lee Kump. |
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12/6/2011
 MIT researchers have found hundreds of tiny fossils of the first known ciliates. The ciliates, named tintinnids, resided in hard, flask-shaped shells with bubbled exteriors that likely helped them float.
Image: Tanja Bosak.
Anyone who has taken high school biology has likely come into contact with a ciliate. The much-studied paramecium is one of 7,000 species of ciliates, a vast group of microorganisms that share a common morphology: single-celled blobs covered in tiny hairs, or cilia. These cilia — Greek for “eyelash” — are used to propel a microbe through water and catch prey.
Today these hairy microbes are ubiquitous in marine environments. However, it’s unclear how long ciliates have inhabited Earth: After they die, members of most species simply disintegrate in their watery environs, leaving behind no fossilized remains.
Now, geologists at NAI's MIT Team and Harvard University have unearthed rare, flask-shaped microfossils dating back 635 to 715 million years, representing the oldest known ciliates in the fossil record. The remains are more than 100 million years older than any previously identified ciliate fossils, and the researchers say the discovery suggests early life on Earth may have been more complex than previously thought. What’s more, they say such prehistoric microbes may have helped trigger multicellular life, and the evolution of the first animals.
“These massive changes in biology and chemistry during this time led to the evolution of animals,” says Tanja Bosak, the Cecil and Ida Green Career Development Assistant Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We don’t know how fast these changes occurred, and now we are finding evidence of an increase in complexity.”
Bosak and her colleagues have published the study in the October 21, 2011 issue of the journal Geology.
For more information: http://astrobiology.nasa.gov/articles/early-life-more-complex-than-previously-thought/ |
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12/2/2011
Scientists from NAI’s New York Center for Astrobiology at Rensselaer Polytechnic Institute have used the oldest minerals on Earth to reconstruct the atmospheric conditions present on Earth very soon after its birth. The findings, which appear in the December 1, 2011 issue of Nature, are the first direct evidence of what the ancient atmosphere of the planet was like soon after its formation and directly challenge years of research on the type of atmosphere out of which life arose on the planet.
The scientists show that the atmosphere of Earth just 500 million years after its creation was not a methane-filled wasteland as previously proposed, but instead was much closer to the conditions of our current atmosphere. The findings, in a paper titled “The oxidation state of Hadean magmas and implications for early Earth’s atmosphere,” have implications for our understanding of how and when life began on this planet and could begin elsewhere in the universe.
For more information: http://astrobiology.nasa.gov/articles/earth-s-early-atmosphere-an-update/ |
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12/1/2011
 Arthropod expansion in morphological disparity following the Cambrian Explosion of Bilateria, as demonstrated by the Burgess Shale trilobite Olenoides and stem-Chelicerate Sidneyia. Image Credit: Smithsonian Institution, courtesy of Douglas Erwin.
A team of researchers including members of NAI's MIT team have married fossil records with molecular clock studies to reveal a new interpretation of the Cambrian explosion. Collectively these data allow an understanding of the environmental potential, genetic and developmental possibility, and ecological opportunity that existed before and during the Cambrian. The study compares the times of origin of major animal groups (from the molecular clock) with the times of their first appearance in the fossil record. The team shows that the major animal groups first diverged during the Cryogenian, roughly 300 million years prior to their appearance in the fossil record, and acquired the key components of their developmental toolkits early in their history. After a long lag, the groups’ major ecological successes are reflected in the records of the Ediacaran and Cambrian. Their paper appears in the current issue of Science. |
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11/18/2011
Scientists from NAI’s Rensselaer Polytechnic Institute (RPI) Team have compiled years of research to help locate areas in outer space that have extreme potential for complex organic molecule formation. The scientists searched for methanol, a key ingredient in the synthesis of organic molecules that could lead to life. Their results have implications for determining the origins of molecules that spark life in the cosmos.
The findings appear in the Nov. 20 edition of The Astrophysical Journal in a paper titled “Observational constraints on methanol production in interstellar and preplanetary ices.” The work is a collaboration between researchers at Rensselaer, NASA Ames Research Center, the SETI Institute, and Ohio State University.
“Methanol formation is the major chemical pathway to complex organic molecules in interstellar space,” said the lead researcher of the study and director of the NASA-funded center, Douglas Whittet of Rensselaer. If scientists can identify regions where conditions are right for rich methanol production, they will be better able to understand where and how the complex organic molecules needed to create life are formed. In other words, follow the methanol and you may be able to follow the chemistry that leads to life.
Using powerful telescopes on Earth, scientists have observed large concentrations of simple molecules such as carbon monoxide in the clouds that give birth to new stars. In order to make more complex organic molecules, hydrogen needs to enter the chemical process. The best way for this chemistry to occur is on the surfaces of tiny dust grains in space, according to Whittet. In the right conditions, carbon monoxide on the surface of interstellar dust can react at low temperatures with hydrogen to create methanol (CH3OH). Methanol then serves as an important steppingstone to formation of the much more complex organic molecules that are required to create life. Scientists have known that methanol is out there, but to date there has been limited detail on where it is most readily produced.
What Whittet and his collaborators have discovered is that methanol is most abundant around a very small number of newly formed stars. Not all young stars reach such potential for organic chemistry. In fact, the range in methanol concentration varies from negligible amounts in some regions of the interstellar medium to approximately 30 percent of the ices around a handful of newly formed stars. They also discovered methanol for the first time in low concentrations (1 to 2 percent) in the cold clouds that will eventually give birth to new stars.
The scientists conclude in the paper that there is a “sweet spot” in the physical conditions surrounding some stars that accounts for the large discrepancy in methanol formation in the galaxy. The complexity of the chemistry depends on how fast certain molecules reach the dust grains surrounding new stars, according the Whittet. The rate of molecule accumulation on the particles can result in an organic boom or a literal dead end.
“If the carbon monoxide molecules build up too quickly on the surfaces of the dust grains, they don’t get the opportunity to react and form more complex molecules. Instead, the molecules get buried in the ices and add up to a lot of dead weight,” Whittet said. “If the buildup is too slow, the opportunities for reaction are also much lower.”
This means that under the right conditions, the dust surrounding certain stars could hold greater potential for life than most of its siblings. The presence of high concentrations of methanol could essentially jumpstart the process to create life on the planets formed around certain stars.
The scientists also compared their results with methanol concentrations in comets to determine a baseline of methanol production in our own solar system.
“Comets are time capsules,” Whittet said. “Comets can preserve the early history of our solar system because they contain material that hasn’t changed since the solar system was formed.” As such, the scientists could look at the concentrations of methanol in comets to determine the amount of methanol that was in our solar system at its birth.
What they found was that methanol concentrations at the birth of our solar system were actually closer to the average of what they saw elsewhere in interstellar space. Methanol concentrations in our solar system were fairly low, at only a few percent, compared to some of the other methanol-dense areas in the galaxy observed by Whittet and his colleagues.
“This means that our solar system wasn’t particularly lucky and didn’t have the large amounts of methanol that we see around some other stars in the galaxy,” Whittet said.
“But, it was obviously enough for us to be here.”
The results suggest that there could be solar systems out there that were even luckier in the biological game than we were, according to Whittet. As we look deeper into the cosmos, we may eventually be able to determine what a solar system bursting with methanol can do. |
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11/18/2011
A new study from NASA Astrobiology Program-funded scientists points to a rapid collapse of Earth’s species 252 million years ago.
Since the first organisms appeared on Earth approximately 3.8 billion years ago, life on the planet has had some close calls. In the last 500 million years, Earth has undergone five mass extinctions, including the event 66 million years ago that wiped out the dinosaurs. And while most scientists agree that a giant asteroid was responsible for that extinction, there’s much less consensus on what caused an even more devastating extinction more than 185 million years earlier.
The end-Permian extinction occurred 252.2 million years ago, decimating 90 percent of marine and terrestrial species, from snails and small crustaceans to early forms of lizards and amphibians. “The Great Dying,” as it’s now known, was the most severe mass extinction in Earth’s history, and is probably the closest life has come to being completely extinguished. Possible causes include immense volcanic eruptions, rapid depletion of oxygen in the oceans, and — an unlikely option — an asteroid collision.
While the causes of this global catastrophe are unknown, an MIT-led team of researchers has now established that the end-Permian extinction was extremely rapid, triggering massive die-outs both in the oceans and on land in less than 20,000 years — the blink of an eye in geologic time. The researchers also found that this time period coincides with a massive buildup of atmospheric carbon dioxide, which likely triggered the simultaneous collapse of species in the oceans and on land.
With further calculations, the group found that the average rate at which carbon dioxide entered the atmosphere during the end-Permian extinction was slightly below today’s rate of carbon dioxide release into the atmosphere due to fossil fuel emissions. Over tens of thousands of years, increases in atmospheric carbon dioxide during the Permian period likely triggered severe global warming, accelerating species extinctions.
The researchers also discovered evidence of simultaneous and widespread wildfires that may have added to end-Permian global warming, triggering what they deem “catastrophic” soil erosion and making environments extremely arid and inhospitable.
The researchers present their findings this week in Science, and say the new timescale may help scientists home in on the end-Permian extinction’s likely causes.
For more information: http://web.mit.edu/newsoffice/2011/mass-extinction-1118.html |
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11/8/2011
Astrobiology Program investigators Michael Mumma and Steven Charnley from NAI's NASA Goddard Space Flight Center Team have recently published a review entitled The Chemical Composition of Comets: Emerging Taxonomies and Natal Heritage in the Annual Review of Astronomy and Astrophysics.
Cometary nuclei contain the least modified material from the formative epoch of our planetary system, and their compositions reflect a range of processes experienced by material prior to its incorporation in the cometary nucleus. Dynamical models suggest that icy bodies in the main cometary reservoirs (Kuiper Belt, Oort Cloud) formed in a range of environments in the protoplanetary disk, and (for the Oort Cloud) even in disks surrounding neighboring stars of the Sun’s birth cluster. Photometric and spectroscopic surveys of more than 100 comets have enabled taxonomic groupings based on free radical species and on crystallinity of rocky grains. Since 1985, new surveys have provided emerging taxonomies based on the abundance ratios of primary volatiles. More than 20 primary chemical species are now detected in bright comets. Measurements of nuclear spin ratios (in water, ammonia, and methane) and of isotopic ratios (D/H in water and HCN; 14N/15N in CN and HCN) have provided critical insights on factors affecting formation of the primary species. The identification of an abundant product species (HNC) has provided clear evidence of chemical production in the inner coma. Parallel advances have occurred in astrochemistry of hot corinos, circumstellar disks, and dense cloud cores. The review addresses the current state of cometary taxonomy and compares it with current astrochemical insights. |
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11/1/2011
A new study in Earth and Planetary Science Letters looks at the role of the mineral jarosite in determining when and under what conditions water was present on Mars. On Earth, jarosite can only form in the presence of water, so the detection by the Mars Rover Opportunity of its presence on Mars means that water had to exist at some point in the past. The new study, by scientists at NAI’s Rensselaer Polytechnic Institute (RPI) Team, is the first in a series of experiments designed to provide a roadmap of sorts for scientists who may someday study Martian samples brought back to Earth.
The team discovered a way to use the noble gas argon, which accumulates in jarosite over time, to determine the age of the mineral and the surface conditions under which it formed. “Our experiments indicate that over billion-year timescales and at surface temperatures of 20 degrees Celsius (68 degrees Fahrenheit) or colder, jarosite will preserve the amount of argon that has accumulated since the crystal formed,” says lead co-author Joseph Kula of Syracuse University, “which simply means that jarosite is a good marker for measuring the amount of time that has passed since water was present on Mars.”
Moreover, since the development of life requires water, knowing when and for how long water was present on the Martian surface has implications for the search for potential habitats harboring life, the scientists say. “Jarosite requires water for its formation, but dry conditions for its preservation,” says co-lead author Suzanne Baldwin, also of Syracuse University. “We’d like to know when water formed on the surface of Mars and how long it was there. Studying jarosite may help answer some of these questions.”
Jarosite is a byproduct of the weathering of rocks exposed at the surface of a planet (such as Earth and Mars). The mineral forms when the right mixture of oxygen, iron, sulfur, potassium, and water is present. Once formed, the crystals begin to accumulate argon, which is produced when certain potassium isotopes in the crystals decay. Potassium decay is a radioactive process that occurs at a known rate. By measuring the isotopes of argon trapped within the crystals, scientists can determine the age of the crystals.
However, because argon is a gas, it can potentially escape rapidly from the crystals under hot conditions or slowly over long durations at cold conditions. In order to determine the reliability of the “argon clock” in jarosite, the scientists had to determine the temperature limits to which the crystals could be subjected and still retain the argon. Using a combination of experiments and computer modeling, the team found that argon remains trapped inside the crystals for long periods of time over a range of planetary surface temperatures.
“Our results suggest that 4 billion-year-old jarosite will preserve its argon and, along with it, a record of the climate conditions that existed at the time it formed,” Baldwin says. The scientists are in the process of conducting further studies on jarosite that formed less than 50 million years ago in the Big Horn Basin in Wyoming, which they hope will reveal when the minerals formed and how fast environmental conditions changed from water-saturated to dry. The results can be used as a context for interpreting findings on other planets. |
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10/17/2011
Researchers from NAI's Arizona State University Team and NASA's Exobiology Program have developed a novel geochemical tool that compares the partitioning of uranium isotopes from seawater into carbonates. A decrease of uranium in seawater is indicative of a lack of oxygen (anoxia) in the ocean.
For the first time ever, this approach has revealed the quantitative levels of dissolved oxygen in ancient oceans at the time of Earth’s largest mass extinction, known as the end-Permian mass extinction, 252 million years ago. Many leading scientific theories on the cause of this catastrophe are based on the assumption of a long-term existence of ocean anoxia before the extinction event itself.
The study began by obtaining a core sample of carbonate rock collected in Dawen in Southern China. This location is known to physically correlate with the Permian-Triassic boundary. The investigators focused upon the strata around the so-called “Extinction Horizon,” or, the “moment” of the mass extinction. This study has quantified the amount of oxygen across the extinction event in the ancient global oceans. Most critically, it revealed that ocean anoxia existed for a much shorter period of time (~10,000 years) before the extinction event than was previously estimated (>100,000 years). This new insight greatly constrains possible explanations for the cause of the mass extinction event. The team’s paper is published in a recent issue of PNAS. |
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9/19/2011
Among the various geochemical proxies for the presence of molecular oxygen in the environment, molecular fossils offer a unique record of oxygen where it was first produced and consumed by biology: in sunlit aquatic habitats. Steroid biosynthesis requires molecular oxygen, making the study of sterane molecular fossils important in reconstructing early environmental conditions. In a new study, NAI-funded scientists and their colleagues present evidence that microaerobic marine environments where steroid biosynthesis was possible could have been widespread and persistent for long periods of time prior to the earliest evidence for atmospheric oxygen. Their study is published in a recent issue of PNAS. |
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8/19/2011
 Image Credit: NASA/GSFC
Jupiter, long settled in its position as the fifth planet from our sun, was a rolling stone in its youth. Over the eons, the giant planet roamed toward the center of the solar system and back out again, at one point moving in about as close as Mars is now. The planet’s travels profoundly influenced the solar system, changing the nature of the asteroid belt and making Mars smaller than it should have been. These details are based on a new model of the early solar system developed by NAI scientists at the Virtual Planetary Laboratory, the Goddard Center for Astrobiology, and their colleagues. Their paper appears in a recent issue of Nature.
“We refer to Jupiter’s path as the Grand Tack, because the big theme in this work is Jupiter migrating toward the sun and then stopping, turning around, and migrating back outward,” says the paper’s first author, Kevin Walsh of the Southwest Research Institute in Boulder, Colo. “This change in direction is like the course that a sailboat takes when it tacks around a buoy.”
According to the new model, Jupiter formed in a region of space about three-and-a-half times as far from the sun as Earth is (3.5 astronomical units). Because a huge amount of gas still swirled around the sun back then, the giant planet got caught in the currents of flowing gas and started to get pulled toward the sun. Jupiter spiraled slowly inward until it settled at a distance of about 1.5 astronomical units—about where Mars is now. (Mars was not there yet.)
For more information: http://astrobiology.nasa.gov/articles/jupiter-s-grand-tack-reshaped-the-solar-system/ |
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8/9/2011
NASA-funded researchers have found more evidence meteorites can carry DNA components created in space.
Scientists have detected the building blocks of DNA in meteorites since the 1960s, but were unsure whether they were created in space or resulted from contamination by terrestrial life. The latest research indicates certain nucleobases — the building blocks of our genetic material — reach the Earth on meteorites in greater diversity and quantity than previously thought.
The discovery adds to a growing body of evidence that the chemistry inside asteroids and comets is capable of making building blocks of essential biological molecules. Previously, scientists found amino acids in samples of comet Wild 2 from NASA’s Stardust mission and in various carbon-rich meteorites. Amino acids are used to make proteins, the workhorse molecules of life. Proteins are used in everything from structures such as hair to enzymes, which are the catalysts that speed up or regulate chemical reactions.
The findings were published in the August 11, 2011 online edition of the Proceedings of the National Academy of Sciences. In the new work, scientists analyzed samples of 12 carbon-rich meteorites, nine of which were recovered from Antarctica. The team found adenine and guanine, which are components of DNA nucleobases.
Also, in two of the meteorites, the team discovered for the first time trace amounts of three molecules related to nucleobases that almost never are used in biology. These nucleobase-related molecules, called nucleobase analogs, provide the first evidence that the compounds in the meteorites came from space and not terrestrial contamination.
“You would not expect to see these nucleobase analogs if contamination from terrestrial life was the source, because they’re not used in biology,” said Michael Callahan, astrobiologist and lead author of the paper from NASA’s Goddard Space Flight Center in Greenbelt, Md. “However, if asteroids are behaving like chemical ‘factories’ cranking out prebiotic material, you would expect them to produce many variants of nucleobases, not just the biological ones, because of the wide variety of ingredients and conditions in each asteroid.”
Additional evidence came from research to further rule out the possibility of terrestrial contamination as a source of these molecules. The team analyzed an eight-kilogram (21.4-pound) sample of ice from Antarctica, where most of the meteorites in the study were found. The amounts of nucleobases found in the ice were much lower than in the meteorites. More significantly, none of the nucleobase analogs were detected in the ice sample. The team also analyzed a soil sample collected near one of the non-Antarctic meteorite’s fall site. As with the ice sample, the soil sample had none of the nucleobase analog molecules present in the meteorite.
Launched in Feb. 7, 1999, Stardust flew past an asteroid and traveled halfway to Jupiter to collect particle samples from the comet Wild 2. The spacecraft returned to Earth’s vicinity to drop off a sample-return capsule on January 15, 2006.
The research was funded by NASA’s Astrobiology Institute, the Goddard Center for Astrobiology in Greenbelt, Md.; the NASA Astrobiology Exobiology and Evolutionary Biology Program and the NASA Postdoctoral Program.
Additional information and images are available at:
http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html |
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7/26/2011
The record of Earth’s sulfur cycle preserved in sedimentary rocks is commonly used to track the evolution of microbial sulfur metabolisms and levels of atmospheric oxygen throughout geologic history. Sulfur isotope evidence suggests the Earth’s atmospheric oxygen appeared about 2.4 billion years ago, but its level remained rather low until about 650 million years ago.
New studies by NASA Astrobiology Institute scientists have questioned the extent to which the record of the sulfur cycle reflects the oxygenation. The team has demonstrated that a laboratory culture of a marine sulfate-reducing bacterium can produce sulfur isotope signatures beyond the threshold previously used to define the boundaries for different sulfur metabolisms. This finding suggests that oxygenation is not the only mechanism that can explain similar signatures in modern and ancient sediments. The team’s paper was published in the July 1 issue of Science. |
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7/1/2011
 The nitrogen synthase complex. Nitrogenase is shown in the center, with two chains in cyan and two chains in grey. Image Credit: University of Arizona
In recent years, scientists have found evidence that a ‘near complete’ biological nitrogen cycle existed in the oceans during the late Archean to early Proterozoic (from 2.5 to 2 billion years ago). Modern bacteria use an enzyme called nitrogenase to cycle nitrogen from one form to another. This enzyme is dependent on the presence of metallic elements like iron (Fe), vanadium (V) and, most often, molybdenum (Mo). However, ancient oceans didn’t contain much molybdenum. Could Fe-nitrogenase or V-nitrogenase have played a larger role in the archaean oceans than they do today? To answer this question, a team of researchers at NAI's Montana State University and Arizona State University teams studied the phylogenetic relationships between the proteins that allow nitrogenase to interact with each of the three elements. Their results suggest that the protein (known as Nif protein) actually developed in methanogenic microorganisms, and was then incorporated into bacteria by lateral gene transfer around 1.5-2.2 billion years ago. Ultimately, if Mo-nitrogenase originated under anoxic conditions in the Archaean, it would have likely happened in an environment where both methanogens and bacteria coexisted, and where molybdenum was present for at least part of the time.
The emergence of enzymes like Mo-nitrogenase was a significant step in the evolution of life, and had powerful repercussions for planet Earth and its biosphere as a whole. This research can help answer important questions about the environmental conditions that were present on the early Earth, and the interactions that occurred between life and the ancient planet.
The results were published in the May edition of the journal Geobiology |
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6/24/2011
Researchers supported in part by the NASA Astrobiology Institute and the NASA Exobiology & Evolutionary Biology program have used computer models to study the potential of organic sulfur compounds to be biosignatures in exoplanetary atmospheres. The results indicate that the most detectable feature involves levels of ethane that are higher than expected based on a target planet’s methane concentration. These detection techniques will be particularly useful for finding life on planets similar to the early Earth, that do have life but do not have atmospheric oxygen or ozone, two major biosignature gases. The team suggests that a mission that can detect the ethane and methane in exoplanet atmospheres could find life on such planets, thereby increasing our chances of finding a habitable world outside our solar system.
The study was recently published in the journal Astrobiology and is now available online. |
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6/23/2011
 Left: EPOXI observation of the Earth. Right: model simulation of observation.
Planet Earth is the only example we have of what a habitable planet ‘looks’ like. Using observations from NASA’s Terra, QuikSCAT, and Aura missions, researchers have now developed a 3-D Spectral Earth Model that simulates the appearance of the Earth under a variety of conditions. Researchers with the NASA Astrobiology Institute’s Virtual Planetary Laboratory (VPL) and NASA’s EPOXI mission team have shown that the model’s predictions are a near-perfect match to actual EPOXI and Aqua observations. It can also accurately simulate the whole-disk image of Earth at different wavelengths. The data was published in the July issue of the journal Astrobiology, and it will help astrobiologists test methods for characterizing Earth-sized planets around distant stars. Ultimately, accurate simulations of the Earth could help scientists identify habitable, extrasolar worlds. |
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6/13/2011
 A fragment from the Tagish Lake meteorite. Credit: Michael Holly, Creative Services, University of Alberta.
Some asteroids may have been like “molecular factories” cranking out life’s ingredients and shipping them to Earth via meteorite impacts. Now it appears that at least one asteroid may have been less like a rigid assembly line and more like a flexible diner that doesn’t mind making changes to the menu.
Astrobiologists at NAI’s Goddard Space Flight Center and Carnegie Institution of Washington teams studying the carbon-rich Tagish Lake meteorite have discovered that different pieces of it have greatly differing amounts of amino acids, the building blocks of proteins and essential ingredients to life as we know it.
In January, 2000, a large meteoroid exploded in the atmosphere over northern British Columbia, Canada, and rained fragments across the frozen surface of Tagish Lake. Because many people witnessed the fireball, pieces were collected within days and kept preserved in their frozen state. This ensured that there was very little contamination from terrestrial life.
“The Tagish Lake meteorite fell on a frozen lake in the middle of winter and was collected in a way to make it the best preserved meteorite in the world,” said Dr. Christopher Herd of the University of Alberta, Edmonton, Canada, lead author of a paper about the analysis of the meteorite fragments published June 10 in the journal Science.
“The first Tagish Lake samples — the ones we used in our study that were collected within days of the fall — are the closest we have to an asteroid sample return mission in terms of cleanliness,” adds Dr. Michael Callahan of NASA’s Goddard Space Flight Center in Greenbelt, Md., a co-author on the paper.
The Tagish Lake meteorites are rich in carbon and, like other meteorites of this type, the team discovered the fragments contained an assortment of organic matter including amino acids, which are the building blocks of proteins. Proteins are used by life to build structures like hair and nails, and to speed up or regulate chemical reactions. What’s new is that the team found different pieces had greatly differing amounts of amino acids.
“We see that some pieces have 10 to 100 times the amount of specific amino acids than other pieces,” said Dr. Daniel Glavin of NASA Goddard, also a co-author on the Science paper. “We’ve never seen this kind of variability from a single parent asteroid before. Only one other meteorite fall, called Almahata Sitta, matches Tagish Lake in terms of diversity, but it came from an asteroid that appears to be a mash-up of many different asteroids.”
By identifying the different minerals present in each fragment, the team was able to see how much each had been altered by water. They found that various fragments had been exposed to different amounts of water, and suggest that water alteration may account for the diversity in amino acid production.
“Our research provides new insights into the role that water plays in the modification of pre-biotic molecules on asteroids,” said Herd. “Our results provide perhaps the first clear evidence that water percolating through the asteroid parent body caused some molecules to be formed and others destroyed. The Tagish Lake meteorite provides a unique window into what was happening to organic molecules on asteroids four-and-a-half billion years ago, and the pre-biotic chemistry involved.”
If the variability in Tagish Lake turns out to be common, it shows researchers have to be careful in deciding whether meteorites delivered enough bio-molecules to help jump-start life, according to the team.
“Biochemical reactions are concentration dependent,” says Callahan. “If you’re below the limit, you’re toast, but if you’re above it, you’re OK. One meteorite might have levels below the limit, but the diversity in Tagish Lake shows that collecting just one fragment might not be enough to get the whole story.”
Although the meteorites were the most pristine ever recovered, there is still some chance of contamination though contact with the air and surface. However, in one fragment, the amino acid abundances were high enough to show they were made in space by analyzing their isotopes.
Isotopes are versions of an element with different masses; for example, carbon 13 is a heavier, and less common, variety of carbon. Since the chemistry of life prefers lighter isotopes, amino acids enriched in the heavier carbon 13 were likely created in space.
“We found that the amino acids in a fragment of Tagish Lake were enriched in carbon 13, indicating they were probably created by non-biological processes in the parent asteroid,” said Dr. Jamie Elsila of NASA Goddard, a co-author on the paper who performed the isotopic analysis.
The team consulted researchers at the Goddard Astrobiology Analytical Lab for their expertise with the difficult analysis. “We specialize in extraterrestrial amino acid and organic matter analysis,” said Dr. Jason Dworkin, a co-author on the paper who leads the Goddard laboratory. “We have top-flight, extremely sensitive equipment and the meticulous techniques necessary to make such precise measurements. We plan to refine our techniques with additional challenging assignments so we can apply them to the OSIRIS-REx asteroid sample return mission.”
OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security — Regolith Explorer) is a Goddard-managed mission, led by the University of Arizona, that will be launched toward asteroid “1999 RQ36” in 2016 and return a sample to Earth in 2023. The OSIRIS-REx team is led by Dr. Michael Drake, Director of the University of Arizona’s Lunar and Planetary Laboratory.
The Tagish Lake research was funded by the Natural Sciences and Engineering Research Council of Canada, the Alberta Ingenuity Fund, and the NASA Astrobiology Program. |
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5/25/2011
 A photograph of an outcrop of metamorphosed volcanosedimentary rocks from the Porpoise Cove locality, Nuvvuagittuq supracrustal belt, Canada. Image: Mojzsis et. al. / NASA Astrobiology
Ancient rocks are shedding new light on the timeline for life’s emergence on Earth. The rocks from the Nuvvuagittuq Supracrustal Belt in Quebec, Canada, are believed to be some of the oldest on Earth. They contain carbon-based minerals that had been interpreted as evidence of the Earth’s early biosphere, however, new research tells a different story. By applying cutting-edge technology to the rock samples, a team of scientists have revealed that the carbon minerals found in the rocks may be much younger than the rocks themselves.
“The characteristics of the poorly crystalline graphite within the samples are not consistent with the metamorphic history of the rock,” said co-author Dominic Papineau in a news release from Boston College. “The carbon in the graphite is not as old as the rock. That can only ring a bell and require us to ask if we need to reconsider earlier studies.”
The results were reported in the May 15, 2011 edition of the journal Nature Geoscience. Funding organizations for this work included the NASA Exobiology and Evolutionary Biology Program (Exo/Evo), the NASA Astrobiology Institute (NAI), the W.M. Keck Foundation, the Geophysical Laboratory of the Carnegie Institution of Washington, Carnegie of Canada, the Naval Research Laboratory, the NRC Research Associateship Program, Boston College, and the Fond Québécois pour la recherche sur la nature et les technologies (FQRNT). |
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5/10/2011
 Figure 1. Optical, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) images of Tindir scale fossils.
Fossils are essential to our understanding of the history and origins of complex life. New work from NAI’s MIT and Penn State teams describes exquisitely preserved microfossils from mid-Neoproterozoic (811-717 million years old) rocks of the Fifteenmile Group, Yukon. These fossils are interpreted as biomineralized plates that covered the surface of a single-celled alga.
Their findings suggest that the minerals used by the ancient marine organisms have changed through time, perhaps linked to changing ocean chemistry. While the relationship of these fossils to modern organisms is difficult to determine, the researchers argue that it’s likely that these unique fossils are the plates of an organism most closely related to green algae.
Their paper appears online in Geology. |
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2/8/2011
 Preserved eurypterid fossil. Credit: University of Wisconsin
New research by members of the Carnegie Institution of Washington and MIT NAI teams is changing the way we understand the organic fossil record of Earth. A new study appearing in Geology shows that organisms evolved to use a structural material known as ‘chitin-protein complex’ much earlier than previously believed. Chitin fibers embedded in a matrix of protein make up the outer layer of exoskeletons in arthropods. Microorganisms quickly degrade this material when an organism dies, so identifying the chitin-protein material in fossils from the early Paleozoic was a stunning find. |
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1/18/2011
 Ammonoid markers. A 50-million-year fossil record of ammonoids includes two kind of the nautilus-like creatures, swimmers and floaters. At two points of mass extinction, the swimming ammonoids disappear completely from the fossil record. (Credit: Image courtesy of Brown University)
A new study supported by the NAI looks at two of the greatest mass extinctions in Earth’s history, concluding that the ecosystem collapse is attributed to a loss in the variety of species sharing the same space. It took up to 10 million years after the mass extinctions for the ecosystem to stabilize. The study correlates ammonoid diversity and disparity and ecosystem stability as represented by stable carbon isotopic records spanning the end-Permian through end-Triassic mass extinctions. The paper appears in Geology online. |
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1/17/2011
 This artist's concept uses hands to illustrate the left and right-handed versions of the amino acid isovaline. Credit: NASA/Mary Pat Hrybyk-Keith.
A wider range of asteroids were capable of creating the kind of amino acids used by life on Earth, according to new NASA research.
Amino acids are used to build proteins, which are used by life to make structures like hair and nails, and to speed up or regulate chemical reactions. Amino acids come in two varieties that are mirror images of each other, like your hands. Life on Earth uses the left-handed kind exclusively. Since life based on right-handed amino acids would presumably work fine, scientists are trying to find out why Earth-based life favored left-handed amino acids.
In March, 2009, researchers at NASA’s Goddard Space Flight Center in Greenbelt, Md., reported the discovery of an excess of the left-handed form of the amino acid isovaline in samples of meteorites that came from carbon-rich asteroids. This suggests that perhaps left-handed life got its start in space, where conditions in asteroids favored the creation of left-handed amino acids. Meteorite impacts could have supplied this material, enriched in left-handed molecules, to Earth. The bias toward left-handedness would have been perpetuated as this material was incorporated into emerging life.
In the new research, the team reports finding excess left-handed isovaline (L-isovaline) in a much wider variety of carbon-rich meteorites. “This tells us our initial discovery wasn’t a fluke; that there really was something going on in the asteroids where these meteorites came from that favors the creation of left-handed amino acids,” says Dr. Daniel Glavin of NASA Goddard. Glavin is lead author of a paper about this research published online in Meteoritics and Planetary Science.
“This research builds on over a decade of work on excesses of left-handed isovaline in carbon-rich meteorites,” said Dr. Jason Dworkin of NASA Goddard, a co-author on the paper.
“Initially, John Cronin and Sandra Pizzarello of Arizona State University showed a small but significant excess of L-isovaline in two CM2 meteorites. Last year we showed that L-isovaline excesses appear to track with the history of hot water on the asteroid from which the meteorites came. In this work we have studied some exceptionally rare meteorites which witnessed large amounts of water on the asteroid. We were gratified that the meteorites in this study corroborate our hypothesis,” explained Dworkin.
L-isovaline excesses in these additional water-altered type 1 meteorites (i.e. CM1 and CR1) suggest that extra left-handed amino acids in water-altered meteorites are much more common than previously thought, according to Glavin. Now the question is what process creates extra left-handed amino acids. There are several options, and it will take more research to identify the specific reaction, according to the team.
However, “liquid water seems to be the key,” notes Glavin. “We can tell how much these asteroids were altered by liquid water by analyzing the minerals their meteorites contain. The more these asteroids were altered, the greater the excess L-isovaline we found. This indicates some process involving liquid water favors the creation of left-handed amino acids.”
Another clue comes from the total amount of isovaline found in each meteorite. “In the meteorites with the largest left-handed excess, we find about 1,000 times less isovaline than in meteorites with a small or non-detectable left-handed excess. This tells us that to get the excess, you need to use up or destroy the amino acid, so the process is a double-edged sword,” says Glavin.
Whatever it may be, the water-alteration process only amplifies a small existing left-handed excess, it does not create the bias, according to Glavin. Something in the pre-solar nebula (a vast cloud of gas and dust from which our solar system, and probably many others, were born) created a small initial bias toward L-isovaline and presumably many other left-handed amino acids as well.
One possibility is radiation. Space is filled with objects like massive stars, neutron stars, and black holes, just to name a few, that produce many kinds of radiation. It’s possible that the radiation encountered by our solar system in its youth made left-handed amino acids slightly more likely to be created, or right-handed amino acids a bit more likely to be destroyed, according to Glavin.
It’s also possible that other young solar systems encountered different radiation that favored right-handed amino acids. If life emerged in one of these solar systems, perhaps the bias toward right-handed amino acids would be built in just as it may have been for left-handed amino acids here, according to Glavin.
The research was funded by the NASA Astrobiology Institute (NAI), which is administered by NASA’s Ames Research Center in Moffett Field, Calif.; the NASA Cosmochemistry program, the Goddard Center for Astrobiology, and the NASA Post Doctoral Fellowship program. The team includes Glavin, Dworkin, Dr. Michael Callahan, and Dr. Jamie Elsila of NASA Goddard. |
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1/11/2011
A new study in a recent issue of Science from NAI’s NASA Goddard Space Flight Center Team and their colleagues looks at late accretion in the formation of the Earth, Moon, and Mars. Puzzled by the presence of highly siderophile elements (HSUs) in the terrestrial, lunar, and martian mantles, they show that the bombardment by leftover planetesimal populations dominated by massive projectiles can explain these additions. Their inferred size distribution matches those derived from the inner asteroid belt, ancient martian impact basins, and planetary accretion models. The largest late terrestrial impactors, at 2500 to 3000 kilometers in diameter, potentially modified Earth’s obliquity by ~10°, whereas those for the Moon, at ~250 to 300 kilometers, may have delivered water to its mantle. |
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12/16/2010
Researchers from the NASA Astrobiology Program have discovered amino acids in a meteorite where none were expected.
“This meteorite formed when two asteroids collided,” said Dr. Daniel Glavin of NASA’s Goddard Space Flight Center, Greenbelt, Md. “The shock of the collision heated it to more than 2,000 degrees Fahrenheit, hot enough that all complex organic molecules like amino acids should have been destroyed, but we found them anyway.” Glavin is lead author of a paper on this discovery appearing December 13 in Meteoritics and Planetary Science. “Finding them in this type of meteorite suggests that there is more than one way to make amino acids in space, which increases the chance for finding life elsewhere in the Universe.”
Amino acids are used to make proteins, the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins. Previously, scientists at the Goddard Astrobiology Analytical Laboratory have found amino acids in samples of comet Wild 2 from NASA’s Stardust mission, and in various carbon-rich meteorites. Finding amino acids in these objects supports the theory that the origin of life got a boost from space — some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite impacts.
When Dr. Peter Jenniskens of the SETI Institute, Mountain View, Calif., and NASA’s Ames Research Center, Moffett Field, Calif., approached NASA with the suggestion to search for amino acids in the carbon-rich remnants of asteroid 2008 TC3, expectations were that nothing was to be found. Because of an unusually violent collision in the past, this asteroid’s ingredients for life were a “culinary disaster” and now mostly in the form of graphite. The small asteroid, estimated at six to fifteen feet across, was the first to be detected in space prior to impact on Earth on October 7, 2008. When Jenniskens and Dr. Muawia Shaddad of the University of Khartoum recovered remnants in the Nubian Desert of northern Sudan, the remnants turned out to be the first Ureilite meteorites found in pristine condition.
A meteorite sample was divided between the Goddard lab and a lab at the Scripps Institution of Oceanography at the University of California, San Diego. “Our analyses confirm those obtained at Goddard,” said Professor Jeffrey Bada of Scripps, who led the analysis there. The extremely sensitive equipment in both labs detected small amounts of 19 different amino acids in the sample, ranging from 0.5 to 149 parts per billion. The team had to be sure that the amino acids in the meteorite didn’t come from contamination by life on Earth, and they were able to do so because of the way amino acids are made. Amino acid molecules can be built in two ways that are mirror images of each other, like your hands. Life on Earth uses left-handed amino acids, and they are never mixed with right-handed ones, but the amino acids found in the meteorite had equal amounts of the left and right-handed varieties.
The sample had various minerals that only form under high temperatures, indicating it was forged in a violent collision. It’s possible that the amino acids are simply leftovers from one of the original asteroids in the collision – an asteroid that had better conditions for amino acid formation. Dr. Jennifer Blank of SETI has done experiments with amino acids in water and ice, showing they survive pressures and temperatures comparable to a low-angle comet-Earth impact or asteroid-asteroid collisions.
However, the team thinks it’s unlikely amino acids could have survived the conditions that created the meteorite, which endured higher temperatures – more than 2,000 degrees Fahrenheit (over 1,100 Celsius) – over a much longer period. “It would be hard to transfer amino acids from an impactor to another body simply because of the high-energy conditions associated with the impact,” said Bada.
Instead, the team believes there’s an alternate method for making amino acids in space. “Previously, we thought the simplest way to make amino acids in an asteroid was at cooler temperatures in the presence of liquid water. This meteorite suggests there’s another way involving reactions in gases as a very hot asteroid cools down,” said Glavin. The team is planning experiments to test various gas-phase chemical reactions to see if they generate amino acids.
Fragments of 2008 TC3 are collectively called “Almahata Sitta” or “Station Six” after the train stop in northern Sudan near the location where pieces were recovered. They are prized because they are Ureilites, a rare type of meteorite. “An interesting possibility is that Ureilites are thought by some researchers to have formed in the solar nebula and thus the findings of amino acids in Almahata Sitta might imply that amino acids were in fact synthesized very early in the history of the solar system,” adds Bada.
The Goddard analysis team includes Glavin and Drs. Jason Dworkin, Michael Callahan, and Jamie Elsila. This research was funded by the NASA Astrobiology Institute, which is managed by NASA Ames; the Goddard Center for Astrobiology, and the NASA Cosmochemistry and Astrobiology: Exobiology and Evolutionary Biology programs. |
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12/2/2010
 Geomicrobiologist Felisa Wolfe-Simon, collecting lake-bottom sediments in the shallow waters of Mono Lake in California. Wolfe-Simon cultured the arsenic-utilizing organisms from this hypersaline and highly alkaline environment. Credit: ©2010 Henry Bortman
One of the basic assumptions about life on Earth may be due for a revision thanks to research supported by NASA’s Astrobiology Program. Geomicrobiologist Felisa Wolfe-Simon has discovered a bacterium in California’s Mono Lake that uses arsenic instead of phosphorus in its DNA. Up until now, it was believed that all life required phosphorus as a fundamental piece of the ‘backbone’ that holds DNA together. The discovery of an organism that thrives on otherwise poisonous arsenic broadens our thinking about the possibility of life on other planets, and begs a rewrite of biology textbooks by changing our understanding of how life is formed from its most basic elemental building blocks.
Wolfe-Simon’s research is supported by NASA’s Exobiology and Evolutionary Biology (Exo/Evo) Program and the NASA Astrobiology Institute. Among the goals of these programs is determining the evolution of genes, metabolic pathways, and microbial species on Earth in order to understand the potential for life on other worlds. Wolfe-Simon’s discovery represents the first time in the history of biology that an organism has been found to use a different element to build one of its most basic structures. The paper appeared in the December 2nd, 2010 issue of "Science Express" and subsequently published in the journal Science. |
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11/22/2010
Through NAI’s Minority Institution Research Support Program, scientists at the University of Puerto Rico and their collaborators have identified a unique record of an ancient meteorite impact event that is preserved in microstructures in detrital grains of quartz, zircon, and monazite in the Vaal River, South Africa. The sand samples were collected from the channel of the Vaal River near the two billion-year old Vredefort Dome impact structure, where impact-shocked minerals are known to occur in rocks.
This is the first report that impact shock-deformed minerals survive the process of uplift, erosion, and sedimentary transport. The unique mineral shock-deformation was documented by scanning electron microscopy at the University of Puerto Rico and the University of Wisconsin. The team’s results are published in the current issue of the GSA Bulletin.
This result demonstrates that a record of an ancient impact event can be preserved in sedimentary rocks billions of years after the impact crater is eroded. This recognition provides a new method to search for evidence of missing impacts in sedimentary rocks throughout the geologic time scale. This new insight may lead to the identification of missing impact events that have been hypothesized to cause biological mass extinctions, and also impact events on the early Earth that may have influenced the rise of life. |
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11/12/2010
NAI and Exobiology Program scientists have studied the ratio of phosphorus to iron in ancient marine deposits, and have found that phosphorus levels are linked to the rapid diversification of animal life that began at the end of the Proterozoic era, about 700 million years ago. Their paper appears in a recent issue of Nature.
An increase in atmospheric oxygen at the time provided “raw material” for the evolution of respiration (breathing) and contributed to a protective ozone layer. The end of global “snowball Earth” glaciations likely paved the way for animal life to flourish, too, but the question remained, how does it all relate?
The data show a peak in phosphorus-to-iron ratios in iron formations dating from 750 to 635 Myr ago, indicating unusually high dissolved phosphate concentrations in the aftermath of the ‘snowball Earth’ glaciations. This postglacial phosphate increase would have caused high rates of primary biological productivity, as well as organic carbon burial and a transition to more oxidizing conditions in the ocean and atmosphere. |
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10/5/2010
Researchers that include members of NAI's Arizona State University Team and NASA's Exobiology program are using the isotopic composition and concentration of molybdenum in sedimentary rocks to explore how the evolution of Earth’s biota is intimately linked to the oxygenation of the oceans and atmosphere. Their results, published in PNAS, indicate two episodes of global ocean oxygenation. The first coincides with the emergence of the Ediacaran fauna ~550 million years ago, including large, motile bilaterian animals. The second, perhaps larger, oxygenation took place ~400 million years ago, well after the initial rise of animals, therefore suggesting that early metazoans evolved in a relatively low oxygen environment. |
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9/29/2010
 The planetary orbits of the Gliese 581 system compared to those of our own solar system. Image Credit: National Science Foundation.
A team of planet hunters, including scientists from the NASA Astrobiology Institute’s teams at the University of Hawai’i, Manoa and the Carnegie Institution of Washington, has announced the discovery of a planet with three times the mass of Earth orbiting a nearby star at a distance that places it squarely in the middle of the star’s “habitable zone,” an area where liquid water could exist on the planet’s surface. If confirmed, this would be the most Earth-like exoplanet yet discovered, and the first strong case for a potentially habitable world outside our solar system.
The team's new findings are reported in a paper published in the Astrophysical Journal.
For more information: http://www.nasa.gov/topics/universe/features/gliese_581_feature.html |
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9/10/2010
Astrobiologists at NAI's Arizona State University Team and their colleagues have been working to constrain the abundance and distribution of dissolved oxygen in the Earth’s early oceans, prior to the rise of atmospheric oxygen about 2.4 billion years ago. Their analyses of 2.6- to 2.5-billion-year-old black shales from South Africa suggest that the production of oxygen in the surface ocean was vigorous at this time. Combined with studies conducted in Australia, they conclude that the productive regions along ocean margins during the late Archaean eon were sites of substantial O2 accumulation, at least 100 million years before it began to accumulate in the atmosphere. Their paper can be found in the August 22 issue of Nature Geosciences. |
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7/16/2010
Many of our galaxy’s suns have destroyed the atmospheres of orbiting Earth-like planets—or so astrobiologists have long feared. The Milky Way, they note, is dominated by M dwarf stars: violent, unpredictable suns that frequently hurl high-energy particles and solar flares into space. Because they are much cooler than our sun, any potentially habitable planet would need to orbit them much closer than Earth does, putting it smack in the danger zone. But a new study from NAI’s Virtual Planetary Laboratory Team indicates that these planets may be unexpectedly shielded from solar activity, keeping life safe. The study will appear in an upcoming edition of Astrobiology. |
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6/11/2010
Many of the most well known comets, including Halley, Hale-Bopp and, most recently, McNaught, may have been born in orbit around other stars, according to a new theory by an international team of astronomers led by Harold F. Levison, co-investigator on NAI’s NASA Goddard Space Flight Center Team.
The team used computer simulations to show that the Sun may have captured small icy bodies from its sibling stars while it was in its birth star cluster, thereby creating a reservoir for observed comets. Their paper appears in the June 10, 2010 issue of Science Express. |
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6/9/2010
A study led by Chris Dupont, collaborator on NAI's Arizona State University Team and member of the J. Craig Venter Institute indicates that environmental availability of trace elements over Earth’s history influenced the selection of elements used by life as biological evolution progressed. Their results show that environmental concentrations of trace metals influenced which types of metal-binding proteins evolved, and the relative timing of their evolution.
The study implies that the geochemistry of the Archean ocean (>2.5 billion years ago) influenced both the evolution of metal-binding protein architectures and the selection of elements by the ancestors of modern Archaea and Bacteria (simple single cell organisms). Specifically, low Zn, Mo, and Cu concentrations in the Archean ocean likely prevented the widespread emergence and diversification of Eukaryotic life (including plants, animals, and fungi) until the oceans became oxic, relatively late in Earth’s history. The study also revealed that although modern Archaea and Bacteria still predominantly use ancient metal-binding protein structures, most Eukaryotes use both early- and late- evolving structures. The paper appears in the May 24 Early Edition of PNAS. |
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5/10/2010
 Photographs of Paleoproterozoic phosphorites.
The evolution of complex life forms may have gotten a jump start billions of years ago, when geologic events operating over millions of years caused large quantities of phosphorus to wash into the oceans. According to this model, proposed in a new paper by Dominic Papineau of NAI’s Carnegie Institution of Washington team, the higher levels of phosphorus would have caused vast algal blooms, pumping extra oxygen into the environment which allowed larger, more complex types of organisms to thrive.
“Phosphate rocks formed only sporadically during geologic history,” says Papineau, a researcher at Carnegie’s Geophysical Laboratory, “and it is striking that their occurrences coincided with major global biogeochemical changes as well as significant leaps in biological evolution.”
In his study, published in the journal Astrobiology, Papineau focused on the phosphate deposits that formed during an interval of geologic time known as the Proterozoic, from 2.5 billion years ago to about 540 million years ago. “This time period is very critical in the history of the Earth, because there are several independent lines of evidence that show that oxygen really increased during its beginning and end,” says Papineau. The previous atmosphere was possibly methane-rich, which would have given the sky an orangish color. “So this is the time that the sky literally began to become blue.”
For more information: http://astrobiology.nasa.gov/articles/did-phosphorous-trigger-blue-skies/ |
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4/27/2010
Studies of modern sedimentary analogs to ancient rock precursors are critical to gain insight into the biogeochemical processes responsible for generating unique chemical or isotopic compositions in ancient rocks. A recent study published by the University of Wisconsin NAI Team in Geobiology provides an example of such a modern analog study in the context of Archean and Paleoproterozoic Banded Iron Formations (BIFs). Sediments downstream of the Iron Mountain acid mine drainage site in northern California were examined for their chemical and Fe isotope composition, as well as the presence and activity of iron-reducing microorganisms. The results link dissimilatory microbial iron reduction (DIR) to the generation of large quantities of aqueous (mobile) ferrous iron, and provide the first demonstration of Fe isotope fractionation in an environment where DIR has been shown by microbiological methods to be active in sediment metabolism. These findings provide insight into pathways whereby DIR could have led to the formation of isotopically-light Fe-bearing minerals in BIFs. |
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4/16/2010
NAI scientists from the University of Wisconsin Team and their colleagues have shown that the true age of this famous meteorite is 4.091 billion years, about 400 million years younger than earlier age estimates. Their study shows that it formed during a time when Mars was wet and had a magnetic field, conditions that are favorable for the emergence and development of life. This finding precludes ALH84001 from being a remnant of primordial Martian crust, as well as confirming that volcanic activity was ongoing in Mars over much of its history. Their paper appears in the April 16, 2010 issue of Science. |
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4/9/2010
The Ediacaran Period (635-542 million years ago) was a time of fundamental environmental and evolutionary change, culminating in the first appearance of macroscopic animals. A new study from NAI’s Arizona State University Team outlines a detailed record of Ediacaran ocean chemistry for the Doushantuo Formation in the Nanhua Basin, South China. Their results suggest a stratified ocean was maintained dynamically throughout the Ediacaran Period. Their model reconciles seemingly conflicting geochemical conditions proposed previously for Ediacaran deep oceans, and helps explain the patchy fossil record of early metazoans. Their paper appears in the April 2nd issue of Science. |
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3/22/2010
Rocco Mancinelli, PI of NAI’s SETI Institute Emeritus Team, and his colleagues have published a major review of space microbiology in the current issue of Microbiology and Molecular Biology Reviews. They discuss that, in general, microorganisms tend to thrive in the space flight environment, but that the mechanisms responsible for the observed behaviors aren’t well understood. The survival of microorganisms in space was investigated to tackle questions on the upper boundary of the biosphere and on the likelihood of interplanetary transport of microorganisms. While it is found that extraterrestrial solar UV radiation was the most deleterious factor of space, the data the team surveyed supports the likelihood of interplanetary transfer of microorganisms within meteorites, the so-called lithopanspermia hypothesis. |
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3/22/2010
Researchers from NAI’s University of Wisconsin Team studied carbon and iron isotopes in core samples from 2.7-2.5 billion year old rocks in Western Australia. New iron isotope data integrated with previously collected carbon isotope data on the same samples document the sophisticated metabolic diversity of microbial communities that once lived in the region, showing that methane and iron cycling were likely coupled. Their results are published in a recent issue of Earth and Planetary Science Letters. |
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2/17/2010
The origin of the atmosphere of Saturn’s largest moon, Titan, has been an enduring mystery for decades. Scientists from NAI's Arizona State University team think they may finally have an answer. They tested the recently popular hypothesis that methane in Titan’s atmosphere originated in hydrothermal systems deep within Titan. Their work was made possible by chemical data that were acquired when NASA’s Cassini spacecraft passed through a plume of water and other compounds from Enceladus.
Using a geochemical model, the team deduced that Titan’s atmospheric methane has much less deuterium than would be expected if the methane were produced in a hydrothermal system. The implication is that Titan’s methane is a primordial chemical species that was accreted by the moon during its formation.
While Titan’s methane probably came from accreted ices, the analysis of the ASU team suggests that the other major constituent of Titan’s atmosphere, molecular nitrogen, could have come from within Titan’s core. This work advances the understanding of the origin and evolution of the bioessential elements carbon and nitrogen on icy worlds in planetary systems. More information can be found in the December 2009 issue of Icarus. |
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1/5/2010
A new paper in Science from NAI’s Arizona State University team indicates that a trusted equation for calculating the age of the solar system may need rewriting. The team’s measurements show that one of the equation’s assumptions — that certain kinds of uranium always appear in the same relative quantities in meteorites — is wrong.
The differences in the quantities of uranium could mean that current estimates of the age of the solar system overshoot that age by 1 million years or more. Historical estimates place the age at about 4.5 billion years—a number that is not precise enough to show a difference of one million—but more finely honed recent calculations place the age at more like 4.5672 billion years. One million years is still an eyeblink at this scale, representing the difference between 4.566 and 4.567, but this difference is important in understanding the infant solar system. |
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12/18/2009
Mark Young from NAI’s Montana State University Team and Jill Banfield from NAI’s Emeritus Team at UC Berkeley have teamed up to study genetic exchange in bacterial and archeal populations. Their new Science paper, "Variety—the Splice of Life—in Microbial Populations", describes the effects of the exchange of genetic material – from useless to critical in terms of selection. They also observed the splicing of viral material. |
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12/17/2009
Rocco Mancinelli, PI of NAI’s Emeritus Team at the SETI Institute, will use a zeppelin airship to observe red salt ponds turn green while the environment is changed from near-Martian conditions into wetlands. Work will begin next year on a decades-long project to restore thousands of acres of industrial salt-harvesting ponds in San Francisco Bay into native wetland habitat. The ponds are colored red because of the color of microbes that flourish in the extremely salty conditions. Green microbes will replace red ones as the wetlands are restored.
For more information: http://www.sfexaminer.com/local/Salt-ponds-could-be-clue-to-life-on-Mars-79280337.html |
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12/14/2009
Two nearby stars have been found to harbor “super-Earths”― rocky planets larger than the Earth but smaller than ice giants such as Uranus and Neptune. Unlike previously discovered stars with super-Earths, both of the stars are similar to the Sun, suggesting to scientists that low-mass planets may be common around nearby stars. “Over the last 12 years or so nearly 400 planets have been found, and the vast majority of them have been very large―Jupiter mass or even larger,” says researcher Paul Butler of NAI’s team at the Carnegie Institution of Washington. “These latest planets are part of a new trend of finding much smaller planets – planets that are more comparable to Earth.”
For more information: http://www.ciw.edu/news/first_super_earths_discovered_around_sun_stars |
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12/2/2009
Researchers from the Carnegie Institution of Washington and their colleagues have published a paper entitled “The Carnegie Astrometric Planet Search Program,” in Publications of the Astronomical Society of the Pacific. The paper describes an astrometric search for gas giant planets and brown dwarfs orbiting nearby low-mass dwarf stars, using the 2.5 m du Pont Telescope at the Las Campanas Observatory in Chile. |
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11/6/2009
NASA astrobiologists studying the origin of life have reproduced uracil, a key component of RNA, in the laboratory. They discovered that an ice sample containing pyrimidines exposed to ultraviolet radiation under space-like conditions produces this essential ingredient of life. The study appears in the September issue of Astrobiology.
“We have demonstrated for the first time that we can make uracil, a component of RNA, non-biologically in a laboratory under conditions found in space,” said Michel Nuevo, research scientist at NASA’s Ames Research Center. “We are showing that these laboratory processes, which simulate occurrences in outer space, can make a fundamental building block used by living organisms on Earth.” |
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11/4/2009
It is widely accepted that around 2.4 billion years ago, the Earth’s atmosphere underwent a dramatic change when oxygen levels rose sharply. Called the “Great Oxidation Event” (GOE), the oxygen spike marks an important milestone in Earth’s history, the transformation from an oxygen-poor atmosphere to an oxygen-rich one paving the way for complex life to develop on the planet.
Two questions that remain unresolved in studies of the early Earth are when oxygen production via photosynthesis got started and when it began to alter the chemistry of Earth’s ocean and atmosphere.
A research team that includes members of NAI’s Arizona State University team corroborates recent evidence that oxygen production began in Earth’s oceans at least 100 million years before the GOE, and goes a step further in demonstrating that even very low concentrations of oxygen can have profound effects on ocean chemistry. Their study is published in the current issue of Science.
To arrive at their results, the researchers analyzed 2.5 billion-year-old black shales from Western Australia, samples provided through the NAI’s Astrobiology Drilling Program. Essentially representing fossilized pieces of the ancient seafloor, the fine layers within the rocks allowed the researchers to page through ocean chemistry’s evolving history.
Specifically, the shales revealed that episodes of hydrogen sulfide accumulation in the oxygen-free deep ocean occurred nearly 100 million years before the GOE and up to 700 million years earlier than such conditions were predicted by past models for the early ocean. Scientists have long believed that the early ocean, for more than half of Earth’s 4.6 billion-year history, was characterized instead by high amounts of dissolved iron under conditions of essentially no oxygen.
Said Timothy Lyons of UC Riverside who led the study, “This is important because oxygen-poor and sulfidic conditions almost certainly impacted the availability of nutrients essential to life, such as nitrogen and trace metals. The evolution of the ocean and atmosphere were in a cause-and-effect balance with the evolution of life.” |
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11/2/2009
Dust samples collected by high-flying aircraft in the upper atmosphere have yielded an unexpectedly rich trove of relicts from the ancient cosmos, report scientists from NAI’s Carnegie Institution of Washington team in Earth and Planetary Science Letters. The stratospheric dust includes minute grains that likely formed inside stars that lived and died long before the birth of our sun, as well as material from molecular clouds in interstellar space. This “ultra-primitive” material likely wafted into the atmosphere after the Earth passed through the trail of an Earth-crossing comet in 2003, giving scientists a rare opportunity to study cometary dust in the laboratory.
At high altitudes, most dust in the atmosphere comes from space, rather than the Earth’s surface. Thousands of tons of interplanetary dust particles (IDPs) enter the atmosphere each year. “We’ve known that many IDPs come from comets, but we’ve never been able to definitively tie a single IDP to a particular comet,” says study coauthor Larry Nittler, of Carnegie’s Department of Terrestrial Magnetism. “The only known cometary samples we’ve studied in the laboratory are those that were returned from comet 81P/Wild 2 by the Stardust mission.” NASA’s Stardust mission collected samples of comet dust, returning to Earth in 2006.
Comets are thought to be repositories of primitive, unaltered matter left over from the formation of the solar system. Material held for eons in cometary ice has largely escaped the heating and chemical processing that has affected other bodies, such as the planets. However, the Wild 2 dust returned by the Stardust mission included more altered material than expected, indicating that not all cometary material is highly primitive.
The IDPs used in the current study were collected by NASA aircraft in April 2003, after the Earth passed through the dust trail of comet Grigg-Skjellerup. The research team, which included Carnegie scientists Nittler, Henner Busemann (now at the University of Manchester, U.K.), Ann Nguyen, George Cody, and seven other colleagues, analyzed a sub-sample of the dust to determine the chemical, isotopic and microstructural composition of its grains.
“What we found is that they are very different from typical IDPs” says Nittler. “They are more primitive, with higher abundances of material whose origin predates the formation of the solar system.” The distinctiveness of the particles, plus the timing of their collection after the Earth’s passing through the comet trail, point to their source being the Grigg-Skjellerup comet.
“This is exciting because it allows us to compare on a microscopic scale in the laboratory dust particles from different comets,” says Nittler. “We can use them as tracers for different processes that occurred in the solar system four-and-a-half billion years ago.”
The biggest surprise for the researchers was the abundance of so-called presolar grains in the dust sample. Presolar grains are tiny dust particles that formed in previous generations of stars and in supernova explosions before the formation of the solar system. Afterwards, they were trapped in our solar system as it was forming and are found today in meteorites and in IDPs. Presolar grains are identified by having extremely unusual isotopic compositions compared to anything else in the solar system. But presolar grains are generally extremely rare, with abundances of just a few parts per million in even the most primitive meteorites, and a few hundred parts per million in IDPs. “In the IDPs associated with comet Grigg-Skjellerup they are up to the percent level,” says Nittler. “This is tens of times higher abundances than we see in other primitive materials.”
Also surprising is the comparison with the samples from Wild 2 collected by the Stardust mission. “Our samples seem to be much more primitive, much less processed, than the samples from Wild 2,” says Nittler, “which might indicate that there is a huge diversity in the degree of processing of materials in different comets.” |
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10/28/2009
Members of NAI’s team at Georgia Tech have a new paper in Molecular Biology and Evolution describing an analysis of ribosomal structure and sequence. Their approach chronicles the ribosome’s evolution, effectively interpreting the ribosome as a fossil. Using the highest resolution structures available, of two species that represent disparate regions of the evolutionary tree, they have sectioned the large subunit of each ribosome into concentric shells, like an onion, using the site of peptidyl transfer as the origin. Their results suggest that the structure and interactions of both RNA and protein can be described as changing, in an observable manner, over evolutionary time. |
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10/5/2009
.jpg.jpg?image=/images/324.jpg&width=452 "A view of the sea cliff at Stevns Klint, Denmark. Credit: R. Summons")
The asteroid impact that many researchers claim was the cause of the dinosaur die-off was bad news for marine life at the time as well. But new research from NAI's Massachusetts Institute of Technology team published in the October 2nd issue of Science shows that microalgae – one of the major primary producers in the ocean – bounced back from the near global extinction in about 100 years or less. |
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8/19/2009
Humans might not be walking on Earth today if not for the ancient fusing of two microscopic, single-celled organisms called prokaryotes, NASA-funded research has found.
By comparing proteins present in more than 3000 different prokaryotes – a type of single-celled organism without a nucleus – molecular biologist James A. Lake from the University of California at Los Angeles’ Center for Astrobiology showed that two major classes of relatively simple microbes fused together more than 2.5 billion years ago. Lake’s research reveals a new pathway for the evolution of life on Earth. These insights are published in the Aug. 20 online edition of the journal Nature.
This endosymbiosis, or merging of two cells, enabled the evolution of a highly stable and successful organism with the capacity to use energy from sunlight via photosynthesis. Further evolution led to photosynthetic organisms producing oxygen as a byproduct. The resulting oxygenation of Earth’s atmosphere profoundly affected the evolution of life, leading to more complex organisms that consumed oxygen, which were the ancestors of modern oxygen-breathing creatures including humans.
“Higher life would not have happened without this event,” Lake said. “These are very important organisms. At the time these two early prokaryotes were evolving, there was no oxygen in the Earth’s atmosphere. Humans could not live. No oxygen-breathing organisms could live.”
The genetic machinery and structural organization of these two organisms merged to produce a new class of prokaryotes, called double membrane prokaryotes. As they evolved, members of this double membrane class, called cyanobacteria, became the primary oxygen-producers on the planet, generating enough oxygen to alter the chemical composition of the atmosphere and set the stage for the evolution of more complex organisms such as animals and plants.
“This work is a major advance in our understanding of how a group of organisms came to be that learned to harness the sun and then effected the greatest environmental change Earth has ever seen, in this case with beneficial results,” said Carl Pilcher, director of the NASA Astrobiology Institute at NASA’s Ames Research Center in Moffett Field, Calif., which co-funded the study with the National Science Foundation in Arlington, Va. |
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8/17/2009
NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA’s Stardust spacecraft.
“Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,” said Dr. Jamie Elsila of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Our discovery supports the theory that some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.”
Elsila is the lead author of a paper on this research accepted for publication in the journal Meteoritics and Planetary Science. The research will be presented during the meeting of the American Chemical Society at the Marriott Metro Center in Washington, DC, August 16.
“The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare,” said Dr. Carl Pilcher, Director of the NASA Astrobiology Institute which co-funded the research.
Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins.
Stardust passed through dense gas and dust surrounding the icy nucleus of Wild 2 (pronounced “Vilt-2”) on January 2, 2004. As the spacecraft flew through this material, a special collection grid filled with aerogel – a novel sponge-like material that’s more than 99 percent empty space – gently captured samples of the comet’s gas and dust. The grid was stowed in a capsule which detached from the spacecraft and parachuted to Earth on January 15, 2006. Since then, scientists around the world have been busy analyzing the samples to learn the secrets of comet formation and our solar system’s history.
“We actually analyzed aluminum foil from the sides of tiny chambers that hold the aerogel in the collection grid,” said Elsila. “As gas molecules passed through the aerogel, some stuck to the foil. We spent two years testing and developing our equipment to make it accurate and sensitive enough to analyze such incredibly tiny samples.”
Earlier, preliminary analysis in the Goddard labs detected glycine in both the foil and a sample of the aerogel. However, since glycine is used by terrestrial life, at first the team was unable to rule out contamination from sources on Earth. “It was possible that the glycine we found originated from handling or manufacture of the Stardust spacecraft itself,” said Elsila. The new research used isotopic analysis of the foil to rule out that possibility.
Isotopes are versions of an element with different weights or masses; for example, the most common carbon atom, Carbon 12, has six protons and six neutrons in its center (nucleus). However, the Carbon 13 isotope is heavier because it has an extra neutron in its nucleus. A glycine molecule from space will tend to have more of the heavier Carbon 13 atoms in it than glycine that’s from Earth. That is what the team found. “We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet,” said Elsila.
The team includes Dr. Daniel Glavin and Dr. Jason Dworkin of NASA Goddard. “Based on the foil and aerogel results it is highly probable that the entire comet-exposed side of the Stardust sample collection grid is coated with glycine that formed in space,” adds Glavin.
“The discovery of amino acids in the returned comet sample is very exciting and profound,” said Stardust Principal Investigator Professor Donald E. Brownlee of the University of Washington, Seattle, Wash. “It is also a remarkable triumph that highlights the advancing capabilities of laboratory studies of primitive extraterrestrial materials.”
The research was funded by the NASA Stardust Sample Analysis program and the NASA Astrobiology Institute. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Stardust mission for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, developed and operated the spacecraft.
To learn more about the mission, visit http://stardustnext.jpl.nasa.gov/ .
For more about the NASA Goddard astrobiology team, visit http://astrobiology.gsfc.nasa.gov/analytical |
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7/9/2009
A new study in Science from NAI’s Penn State Team shows that the anaerobic oxidation of methane is not solely a sulfate-dependent process. Microbes cultured from marine methane seeps in California’s Eel River Basin have demonstrated capability of using manganese and iron to oxidize methane to carbon dioxide. These same compounds may have been key to methane oxidation in the early, oxygen-less days of Earth’s atmosphere. |
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6/23/2009
Members of NAI’s team at Penn State and their colleagues have a new paper in PNAS exploring the viability of using isotopes of the element nickel as biomarkers. Nickel is an important trace nutrient for methanogens, which preferentially use one isotope of nickel over another in their metabolic processes. Nickel, unlike iron, doesn’t seem to go through significant redox changes without a biological tie, therefore considering it as a biomarker is less complicated and potentially more reliable. Testing ancient sediments and observing nickel isotopic fractionation could pinpoint where and when methanogens arose. |
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6/19/2009
According to a new study from NAI’s Virtual Planetary Laboratory Team and colleagues at Cal Tech, the lifespan of Earth's biosphere could be prolonged, even as the Sun’s luminosity increases and threatens to wipe out all life on Earth. Published in PNAS, the study points to the substantial reduction of the total pressure of Earth’s atmosphere, achieved by removing massive amounts of nitrogen from it. This would regulate the surface temperatures, allow carbon dioxide to remain in the atmosphere to support life, and could tack an additional 1.3 billion years onto Earth’s expected lifespan. |
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6/9/2009
NAI astrobiologists from the NASA Goddard Center for Astrobiology and their collaborators have developed a new cleaning protocol for space hardware which could benefit future missions searching for life on the Red Planet and elsewhere in the Solar System. Published in Astrobiology, the new protocol was developed as part of a project to investigate life that exists in extreme Arctic environments, where Mars analogue studies are ongoing. The decontamination protocol involves a cocktail of chemicals that were applied and tested on various sampling devices, including a glacial ice core drill and a rover scoop. The procedure goes beyond sterilization, also cleaning off trace organic molecules. |
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5/20/2009
In a new paper in the May 21st issue of Nature, NAI Postdoctoral Fellow Oleg Abramov at the University of Colorado, Boulder leads a modeling study investigating the degree of thermal metamorphism of the Late Heavy Bombardment (LHB) on the crust of the young Earth. The models were designed to recreate the effect of the LHB on the Earth as a whole, with special attention to the impact on a possible subsurface or near-surface primordial microbial biosphere.
The team’s analyses revealed that there is no plausible situation in which the habitable zone could have been fully sterilized, at least since the primary accretion of the planets ended, and the postulated impact origin of the Moon. The authors conclude that subsurface microbial life could have persisted throughout the bombardment. They also propose that multiple, impact-induced temperature anomalies could have driven widespread hydrothermal activity, and that this was conducive to life’s emergence and early diversification. The study was funded by NAI and NASA’s Exobiology Program.
Nature News and Views and press releases from NASA and CU Boulder are also available. |
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4/17/2009
The timing of the rise of oxygen in Earth’s atmosphere is a key question in astrobiology. It is coupled not only to the question of when organisms capable of oxygenic photosynthesis first evolved on Earth, but also what signs of life might be found on young Earth-like planets around other stars.
Members of NAI’s Penn State and Carnegie Institution of Washington Teams report in the April 17th issue of Science that certain sulfur isotopes found in many sedimentary rocks older than 2.4 billion years may not be the result of photochemical reactions in an oxygen-free atmosphere as previously thought. Their research shows that the isotopic signature could instead be due to reactions between organic carbon-rich sediments and sulfate-rich seawater in ancient hydrothermal systems. If so, then the disappearance of the signature in sediments younger than 2.4 billion years may indicate changes in Earth’s hydrothermal system, rather than signaling the rise of oxygen in Earth’s atmosphere. This new paradigm of Earth’s early atmosphere accommodates the theoretical presence of oxygen prior to 2.4 billion years ago.
“The significance of this finding is that an abnormal isotope fractionation (of sulfur) may not be linked to the atmosphere at all,” says Penn State’s Yumiko Watanabe, the study’s lead author. “The strongest evidence for an oxygen poor atmosphere 2.4 billion years ago is now brought into question.” For more information, see Science’s News of the Week GEOCHEMISTRY. |
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4/6/2009
Members of NAI’s Team at Montana State University have provided a Perspectives piece in Dalton Transactions reviewing the organo-metallic chemistry of the active sites of hydrogenase enzymes. Since hydrogen metabolism is presumed to be an early feature in the energetics of life, and hydrogen metabolizing organisms can be traced very early in molecular phylogeny, studying the metal clusters at hydrogenase active sites can reveal potential conditions in which early life arose. Efforts in this field also could have significant impacts on alternative and renewable energy solutions. |
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4/2/2009
Never before has an asteroid been both telescopically observed while in space, and then collected and analyzed after it’s hit the Earth. NAI astrobiologists from the Carnegie Institution of Washington and the SETI Institute are part of the large, interdisciplinary team of scientists who undertook the investigation. Their results are published in a recent issue of Nature.
Analysis of the carbon content in the fragments of 2008 TC3, as it is known, showed it to be mostly graphite-like, indicating that at some point in the past the body had been subjected to extremely high temperatures. Nanodiamonds were also observed.
It’s oxygen isotopic signature classifies it as a very rare type of meteorite known as a ureilite. Because astronomers took spectral measurements of 2008 TC3 before it hit the Earth, and can compare those measurements with the laboratory analyses, scientists will be better able to recognize ureilite asteroids in space. |
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3/17/2009
Members of NAI’s NASA Goddard Space Flight Center Team have a new paper in PNAS describing the distribution and enantiomeric composition of certain amino acids in carbonaceous meteorites. Their results show an increased amount of “left handed” isovaline in several meteorites, which helps to explain why all known life uses only left-handed versions of amino acids to build proteins.
“Finding more left-handed isovaline in a variety of meteorites supports the theory that amino acids brought to the early Earth by asteroids and comets contributed to the origin of only left-handed based protein life on Earth,” said study co-author Danny Glavin.
The team also found a pattern to the excess. Different types of meteorites had different amounts of water, as determined by the clays and water-bearing minerals found in the meteorites. The team discovered that meteorites with more water also had greater amounts of left-handed isovaline. |
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3/17/2009
NAI’s Archean Biosphere Drilling Project supported the acquisition of pristine drill core samples obtained from ancient rocks in Western Australia. New results from those studies, published in the current issue of Nature Geoscience, point toward an earlier start for oxygenic photosynthesis on the early Earth than previously thought.
An international team of researchers, including members of NAI’s Penn State Team, found hematite crystals and associated minerals preserved in a jasper formation within ancient marine sedimentary rocks. Their interpretation is that the rocks formed in an oxygenated water body 3.46 billion years ago. Because the findings imply the presence of molecular oxygen, the team proposes that organisms capable of oxygenic photosynthesis were present in the water body that formed the sediments almost 3.5 billion years ago. Previously, the oldest widely accepted evidence for oxygenic photosynthesis has been organic remains extracted from ~2.7 billion year old sediments. The new results thus indicate that oxygenic photosynthesis evolved more than 700 million years earlier than previously thought.
Hematite can form either in the presence of aerobic bacteria in water, or abiologically in the upper ten meters of seawater. The team did not observe any sign of wave action or other features indicating the rocks formed in shallow water, concluding that the hematite formed in at least 200 meters of water.
For more information, see ScienceNOW and the Australian Broadcasting Company science news service. |
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2/27/2009
NAI’s Deep Time Drilling Project supported the drilling of several pristine cores from ancient rocks in Western Australia in 2004, and a new paper in Science, led by University of Washington astrobiologists, outlines results from the analysis of these cores. The nitrogen isotope values in the core from the 2.5-billion-year-old Mount McRae Shale vary over 30 meters, evidently recording a temporary change from an anaerobic to an aerobic nitrogen cycle, and back again to anaerobic. Other data suggest that nitrification occurred in response to a small increase in surface-ocean oxygenation. The data imply that nitrifying and denitrifying microbes had already evolved by the late Archean and were present before oxygen first began to accumulate in the atmosphere. |
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2/10/2009
The amount of iron released to the ocean by hydrothermal venting at the seafloor is approximately equal to all of the iron flushed from the continents by rivers. The importance of iron to aquatic life can be compared to the importance of nitrogen to terrestrial life, yet iron remains a limiting nutrient in most parts of the oceans. A new study of iron within hydrothermal vents shows that iron emitted from the vents can bind to organic particles and be distributed within the oceans. This bound iron doesn’t oxidize, and is much more easily processed by living organisms, thus affecting the potential for a “natural iron fertilization mechanism.”
The study is published in the February 8, 2009 issue of Nature Geoscience, and the lead author is former NAI Postdoctoral Fellow Brandy Toner, now at the University of Minnesota. Co-authors include members of NAI’s Emeritus team at the Marine Biological Laboratory. |
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2/4/2009
Detected through their molecular remains, fossils of early sponges have been observed in ancient rocks in Oman. The fossils occur in strata that underlie a cap carbonate dated at >635 million years ago. This discovery suggests that shallow waters contained dissolved oxygen in concentrations sufficient to support early animal life at least 100 million years before the Cambrian explosion. Members of NAI’s MIT team led the effort, and have published their findings in the current issue of Nature. |
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1/29/2009
NAI’s Archean Biosphere Drilling Project supported the drilling of several pristine cores from ancient rocks in Western Australia, with the goal of furthering our understanding of the atmosphere, oceans, climate, and biosphere of early Earth. A new paper in Earth and Planetary Science Letters from NAI’s Penn State Team outlines results from the analyses of these cores. Their studies evidence oxygenated surface environments, at least localized and/or short-lived, emerging more than 300 million years before the widely accepted Great Oxidation Event during 2.45 and 2.32 billion years ago. This implies that the emergence of life (oxygenic photoautotrophs) and of oxygenated surface environments occurred before 2.8 billion years ago. |
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1/15/2009
A team of NASA and university scientists has achieved the first definitive detection of methane in the atmosphere of Mars. This discovery indicates the planet is either biologically or geologically active.
For more information: http://astrobiology.nasa.gov/articles/martian-methane-reveals-the-red-planet-is-not-a-dead-planet/ |
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1/14/2009
Bacteria are not usually thought of as having a natural habitat like a mammal or insect, but indirect evidence has suggested that, if anything, most of the early evolution of bacteria was in the marine environment (oceans) and not on land. Surprisingly, NAI researchers from Penn State, Fabia Battistuzzi (now at Arizona State University) and Blair Hedges, found evidence that a large group of bacteria—two-thirds of all ~10,000 described species—trace their ancestry back to a life on land, not in the oceans. These bacteria have many useful adaptations, including the production of oxygen, which now may be tied to their land-loving lifestyle. Their article appeared in the February issue of Molecular Biology and Evolution. The study involved evolutionary analyses of sequence data from hundreds of complete genomes. Members of the terrestrial group, which they call Terrabacteria, include the Gram positive phyla (Actinobacteria and Firmicutes) and two phyla with cell walls that differ structurally from typical Gram positive and Gram negative phyla: Chloroflexi and Deinococcus-Thermus. The large group of >6,000 species also includes the oxygen-producers, Cyanobacteria. Many members of Terrabacteria produce spores and have other adaptations for resistance to environmental stress. Earlier studies, including some by the same authors, found a similar phylogenetic pattern but community acceptance of any particular tree of prokaryotes has been slow, partly because ribosomal RNA trees have always differed from protein and genome trees. But the Penn State team revealed biases in the ribosomal RNA data, that when accounted for, produce a tree more similar to the genome tree and lending support for Terrabacteria. Their molecular clock estimates place the colonization of land deep in the Precambrian, about three billion years ago. |
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11/25/2008
The discovery of CO2 in the atmosphere of extrasolar planet HD 189733b was announced in the November 21, 2008 issue of Nature News. The exoplanet is a hot Jupiter orbiting a star 63 light years from Earth. While it’s extremely unlikely that this particular planet supports life as we know it, the ability to measure the presence of CO2 in its atmosphere bolsters the search for life outside the Solar System. Giovanna Tinetti, former NAI Postdoctoral Fellow, is lead author in the study which used the NICMOS instrument onboard the Hubble Space Telescope to make the measurement. The results were announced in Paris this week at the Molecules in the Atmospheres of Extrasolar Planets workshop, and will be published in the Astrophysical Journal. |
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10/16/2008
Members of NAI’s Carnegie Institution of Washington, Indiana University, and NASA Goddard Space Flight Center Teams and their colleagues have revisited the Miller-Urey experiments, and found some surprising results.
A classic experiment proving amino acids are created when inorganic molecules are exposed to electricity isn’t the whole story, it turns out. The 1953 Miller-Urey Synthesis had two sibling studies, neither of which was published. Vials containing the products from those experiments were recently recovered and reanalyzed using modern technology. The results are reported in Science.
One of the unpublished experiments by American chemist Stanley Miller (under his University of Chicago mentor, Nobelist Harold Urey) actually produced a wider variety of organic molecules than the experiment that made Miller famous. The difference between the two experiments is small — the unpublished experiment used a tapering glass “aspirator” that simply increased air flow through a hollow, air-tight glass device. Increased air flow creates a more dynamic reaction vessel, or “vapor-rich volcanic” conditions, according to the present report’s authors.
“The apparatus Stanley Miller paid the least attention to gave the most exciting results,” said Adam Johnson, lead author of the Science report. “We suspect part of the reason for this was that he did not have the analytical tools we have today, so he would have missed a lot.”
Johnson is a doctoral student in IU Bloomington’s Biochemistry Program. His advisor is biogeochemist Lisa Pratt, professor of geological sciences and the director of NASA’s Indiana-Princeton-Tennessee Astrobiology team.
In his May 15, 1953, article in Science, “A Production of Amino Acids Under Possible Primitive Earth Conditions,” Miller identified just five amino acids: aspartic acid, glycine, alpha-amino-butyric acid, and two versions of alanine. Aspartic acid, glycine and alanine are common constituents of natural proteins. Miller relied on a blotting technique to identify the organic molecules he’d created — primitive laboratory conditions by today’s standards. In a 1955 Journal of the American Chemical Society paper, Miller identified other compounds, such as carboxylic and hydroxy acids. But he would not have been able to identify anything present at very low levels.
Johnson, Scripps Institution of Oceanography marine chemist Jeffrey Bada (the present Science paper’s principal investigator), National Autonomous University of Mexico biologist Antonio Lazcano, Carnegie Institution of Washington chemist James Cleaves, and NASA Goddard Space Flight Center astrobiologists Jason Dworkin and Daniel Glavin examined vials left over from Miller’s experiments of the early 1950s. Vials associated with the original, published experiment contained far more organic molecules than Stanley Miller realized — 14 amino acids and five amines. The 11 vials scientists recovered from the unpublished aspirator experiment, however, produced 22 amino acids and the same five amines at yields comparable to the original experiment.
“We believed there was more to be learned from Miller’s original experiment,” Bada said. “We found that in comparison to his design everyone is familiar with from textbooks, the volcanic apparatus produces a wider variety of compounds.”
Johnson added, “Many of these other amino acids have hydroxyl groups attached to them, meaning they’d be more reactive and more likely to create totally new molecules, given enough time.”
The results of the revisited experiment delight but also perplex.
What is driving the second experiment’s molecular diversity? And why didn’t Miller publish the results of the second experiment?
A possible answer to the first question may be the increased flow rate itself, Johnson explained. “Removing newly formed molecules from the spark by increasing flow rate seems crucial,” he said. “It’s possible the jet of steam pushes newly synthesized molecules out of the spark discharge before additional reactions turn them into something less interesting. Another thought is that simply having more water present in the reaction allows a wider variety of reactions to occur.”
An answer to the second question is relegated to speculation — Miller, still a hero to many scientists, succumbed to a weak heart in 2007. Johnson says he and Bada suspect Miller wasn’t impressed with the experiment two’s results, instead opting to report the results of a simpler experiment to the editors at Science.
Miller’s third, also unpublished, experiment used an apparatus that had an aspirator but used a “silent” discharge. This third device appears to have produced a lower diversity of organic molecules.
Research on early planetary geochemistry and the origins of life isn’t limited to Earth studies. As humans explore the Solar System, investigations of past or present extra-terrestrial life are inevitable. Recent speculations have centered on Mars, whose polar areas are now known to possess water ice, but other candidates include Jupiter’s moon Europa and Saturn’s moon Enceladus, both of which are covered in water ice. The NASA Astrobiology Institute, which supports these investigations, has taken a keen interest in the revisiting of the Miller-Urey Synthesis.
“This research is both a link to the experimental foundations of astrobiology as well as an exciting result leading toward greater understanding of how life might have arisen on Earth,” said Carl Pilcher, director of the NASA Astrobiology Institute, headquartered at NASA Ames Research Center in Mountain View, Calif.
Henderson Cleaves (Carnegie Institution for Science) also contributed to the report. It was funded with grants from the NASA Astrobiology Institute, the Marine Biological Laboratory in Woods Hole, Mass., and Mexico’s El Consejo Nacional de Ciencia y Tecnologia. |
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10/10/2008
An ecosystem discovered 2.8 kilometers underground in the Mponeng Gold Mine near Johannesburg, South Africa two years ago has now been shown to comprise only a single species of microbe, existing on energy from radioactivity, completely independently of the Sun. The community of rod-shaped bacteria of the species Desulforudis audaxviator was discovered in 2005-06 by members of the NAI’s Indiana-Princeton-Tennessee Astrobiology Initiative (IPTAI) Team. Their current results are presented in the October 10th issue of Science.
Confirming earlier inferences, the new work shows that D. audaxviator’s metabolic processes are decoupled from the Sun and the photosynthetic biosphere. This ecosystem uses the energy of naturally occurring radioactivity to split water into hydrogen and hydrogen peroxide. The hydrogen peroxide reacts with naturally occurring sulfide in the rocks to make sulfate. The microbes then reduce the sulfate back to sulfide using electrons provided by the hydrogen left over from the splitting of water. This is the only ecosystem known to exist on an energy source other than light or chemical energy derived from the planet itself.
Genomic analyses have revealed that the organism’s genes code for everything needed to sustain an independent existence and reproduce, including the ability to fix its own nitrogen, move freely, sense its environment, protect itself from viruses, and even sporulate during nutrient-poor periods. It cannot, however, survive oxic conditions, suggesting it hasn’t been exposed to oxygen for a very long time.
Such a community could in principle live in the subsurface of any rocky planet, Mars for example. Radioactivity, sulfide minerals, water, N2 and carbon dioxide—the main things this community needs to survive—are almost certainly common in rocky planets everywhere.
The species name, audaxviator, is taken from Jules Verne’s “Journey to the Center of the Earth,” and means “descend, bold traveler, and attain the center of the Earth.” |
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10/8/2008
According to an article published in the Washington Post, scientists studying the Murchison meteorite have found that it contains clues to the origin of chirality. Amino acids in nature have two forms, referred to as right- and left-handed, that are mirror images of each other. The proteins in living organisms, however, are only made from left-handed amino acids. The reason for this chirality is not understood, but this new research suggests it may stem from meteorites that rained down on the young Earth. |
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10/2/2008
Astrophysicists from the NAI’s Carnegie Institution of Washington team and their colleagues have shown for the first time that a supernova could have triggered the solar system’s formation under conditions of rapid heating and cooling. For several decades, scientists have thought that the solar system formed as a result of a shock wave from an exploding star—a supernova—that triggered the collapse of a dense, dusty gas cloud that contracted to form the sun and the planets. But detailed models of this formation process have only worked under the simplifying assumption that the temperatures during the violent events remained constant. The results, published in the October 20, 2008, issue of the Astrophysical Journal, have resolved this long-standing debate. |
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9/19/2008
Researchers from NAI’s University of Hawai’i team have a paper in the September 17 edition of Nature about the evolution of the animal gut. For more than 100 years zoologists have speculated about scenarios of how the bilaterally symmetrical animals (animals that have a left and a right side, like flies, fish, and humans) evolved from a simple circular (radially symmetric) ancestor that looked similar to jelly fish or corals. In the commonly presented scenarios this transition is connected to the evolution of a through-gut with an anterior mouth and posterior anus. It has been thought that both openings emerged simultaneously from a single embryological opening through which the inner tissues enter (called blastopore).
Recent molecular phylogenies however, place the marine acoel flatworms at the base of the bilaterally symmetric animals. Acoels are thus survivors from the Pre-Cambrian era that retain many ancestral characters (e.g. a nervous system composed of multiple nerve cords and only one opening to their digestive system). One can see Acoels as an evolutionary stepping stone that offers clues about the sequence of character evolution of bilateral animals.
To find out how the acoel digestive system, with its single opening (“mouth”), is related to the through gut present in some bilaterians like humans and flies, the researchers looked at the expression patterns of genes that play a role in the formation of both the mouth and the anus in bilaterian animals.
They were able to show that the sac-like gut of the bilaterian ancestor possessed a single opening that was inherited as the mouth in such diverse animals like flies and sea stars. Furthermore, the team accumulated evidence from gene expression patterns that the anal orifice evolved independently in different animal lineages, possibly in association with the gonoduct (the duct through which eggs and sperm are released). The independent evolution of the anus can be explained by the increase in body size and an elongation of the body. Increased energetic needs and a long blind gut would have made sorting food and waste through a single opening inefficient.
Their work, in conjunction with a better understanding of the evolutionary relationships of animals, clearly rejects previous ideas found in every zoology text book about the evolution of the last common ancestor of flies and humans from a radial symmetric animal (e.g. the Gastraea-Hypothesis of Ernst Haeckel). The team states that this ancestor that lived over 550 myr ago, before the radiation of the bilateral animals was far less complex morphologically than previously thought. At this time our ancestors were hermaphroditic worms, that had only a mouth and no anus. We literally had to spit out our undigested food. Our ancestor was likely a very small, soft-bodied animal that lived between the sand grains in the ocean, similar to the life-style of most acoel species. This also explains why no fossils have yet been found of these animals. The team is certain that their ongoing studies of the nervous system of these worms will yield to similar important insights into the evolutionary roots of the human brain and spinal cord. |
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9/19/2008
Members of NAI’s Penn State, Carnegie Institution, and MIT teams report in a recent issue of Earth and Planetary Science Letters, the distribution of biomarkers in 2.72–2.56 billion-year-old, Neoarchean rocks from the Hamersley Province on the Pilbara Craton in Western Australia. Their observations are consistent with a cyanobacterial source for 2-methylhopanes, in which cyanobacteria were likely the cornerstone of microbial communities in shallow-water ecosystems providing molecular oxygen, fixed carbon, and possibly fixed nitrogen.
Their data, revealing relative abundances of 3-methylhopanes, but not 2-methylhopanes, strongly correlate to stable carbon isotopic composition of insoluble particulate organic matter (kerogen). The unanticipated nature of this relationship provides evidence for a shallow-water locus of carbon cycling through aerobic oxidation of methane and, coincidentally, a means to demonstrate biomarker syngenicity. |
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9/19/2008
Researchers from NAI’s University of Arizona team and their colleagues at the University of Leeds have a new paper in Angewandte Chemie International Edition dealing with prebiotic chemistry and the early Earth. Working both experimentally and with models of the early atmosphere, the team shows that the Hadean and early Archaean Earth was primed with an abundance of condensed phosphates, enabling the formation of the necessary precursors of RNA and DNA. This research removes one of the large stumbling blocks in prebiotic chemistry- that the early Earth lacked a low-temperature reservoir of activated phosphate compounds capable of eventually leading to the origin of life. |
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8/27/2008
Members of NAI’s University of Wisconsin, Madison team have a new paper in Earth and Planetary Science Letters presenting their analyses of 4.35 – 3.36 billion year old detrital zircons from the Jack Hills, Western Australia. Their data reveal relatively high lithium abundances compared to other zircons, as well as lithium isotope ratios that are similar to continental crust weathering products rather than ocean floor basalts. The results support the hypothesis that continental-type crust and oceans existed by 4.3 billion years ago, and suggest that weathering was extensive in the early Archean. |
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8/27/2008
Using data from the CRISM instrument on NASA’s Mars Reconnaissance Orbiter, astrobiologists from NAI’s SETI Institute and Marine Biological Laboratory teams present findings of silicate mineralogy indicating a wide range of past aqueous activity in the Mawrth Vallis on Mars. This work, published in the August 8 issue of Science, suggests that abundant water was once present on Mars and that hydrothermal activity may have occurred. The Mawrith Vallis could be a landing site for future rover missions to Mars. |
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8/27/2008
NAI’s University of Wisconsin team presents a review of iron isotope fingerprints created through biogeochemical cycling in the May, 2008 issue of The Annual Review of Earth and Planetary Sciences. This landmark paper brings together for the first time the co-evolution records of photosynthesis, bacterial sulfate reduction, and bacterial iron reduction in the early Earth. They review data on natural systems and experiments, looking at both abiological and biological processes, and conclude that the temporal carbon, sulfur, and iron isotope record reflects the interplay of changing microbial metabolisms over Earth’s history. |
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7/24/2008
Researchers from NAI’s Penn State, MBL, and UCLA Teams have completed a study of the subseafloor marine biosphere, which may be one of the largest reservoirs of microbial biomass on Earth, and which has recently been the subject of debate in terms of the composition of its microbial inhabitants. Their metagenomic analysis indicates that the subsurface environment is the most unique studied to date, distinct in its microbial make-up from the surface waters. The slowly-metabolizing populations may be akin to what could be found on other planets in our solar system, because such environments have much less energy available than on Earth. And, because they are so deeply buried, these microbes could have survived major Earth impacts, and ensuing extinction events. Their results are published in the July 23rd Early Edition of PNAS. |
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7/18/2008
Using new techniques, scientists from NAI’s Carnegie Institution of Washington Team have discovered for the first time that tiny beads of volcanic glasses collected from two Apollo missions to the Moon contain water. The researchers found that, contrary to previous thought, water was not entirely vaporized in the violent events that formed the Moon. The new study suggests that the water came from the Moon’s interior and was delivered to the surface via volcanic eruptions over 3 billion years ago. The finding calls into question some critical aspects of the “giant impact” theory of the Moon’s formation and may have implications for the origin of possible water reservoirs at the Moon’s poles. The research is published in the July 10, 2008, of Nature. |
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7/18/2008
Researchers from the NAI’s University of Arizona Team have published a new study in the current issue of Astrophysical Journal Letters of the potential habitability of the extrasolar planetary system OGLE-2006-BLG-109L. The first multiple-planet system ever to be discovered by gravitational microlensing, it has two large planets similar to Jupiter and Saturn. It’s possible that the system harbors other planets, including Earth-like planets, that are beyond the sensitivity of the microlensing observations.
Their study examines the prospects for an Earth-like habitable planet in this system. They found that two smaller putative Earth-mass planets, perhaps yet undetected, could produce a planetary architecture of a potentially habitable system. With two “terrestrial” planets and two Jovian planets, it could bear very close resemblance to our own solar system. |
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6/26/2008
A recent study in Earth and Planetary Science Letters from NAI’s Teams at NASA Goddard Space Flight Center, Carnegie Institution of Washington, and University of Wisconsin, shows that nucleic acids of extraterrestrial origin are present in the Murchison meteorite. Carbon-rich meteorites such as the Murchison are thought to be responsible for delivering biologically-relevant organic material to the young Earth. These results demonstrate that the nucleic acids discovered in the meteorite, which are components of the genetic code in modern biochemistry, were already present in the early solar system and may have played a key role in life’s origin. Read more at ScienceNOW. |
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6/4/2008
Researchers from NAI's Penn State Team announced at the American Society of Microbiology General Meeting in Boston their discovery of a novel species of ultra-small bacteria that has survived for more than 120,000 years within the ice of a Greenland glacier at a depth of nearly two miles. The species is related genetically to certain bacteria found in fish, marine mud, and the roots of some plants, yet it has persisted in a low-temperature, high-pressure, reduced-oxygen, and nutrient-poor habitat. The study's authors speculate that it's unusual size helped enable it's survival in the ice for so long. |
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5/28/2008
Researchers from NAI's University of California, Berkeley Team have a new study in Science focused on Box Canyon in Idaho. Incised into a basaltic plain with no drainage network upstream, and approximately 10 cubic meters per second of seepage emanating from its vertical headwall, the canyon is a veritable poster child of groundwater seepage erosion. But this new study posits evidence that the canyon?s formation was caused rather by catastrophic megaflood 45,000 years ago. Their results imply that flooding of this kind may have caused similar features on Mars. |
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5/28/2008
Researchers from NAI's Marine Biological Laboratory Team continue their study of the deep biosphere, reporting the latest results in Nature. This new study reveals that bacterial communities dwelling on ocean-bottom rocks are more abundant and diverse than previously thought, especially relative to the overlying water column. The microbes appear to ?feed? on the oceanic crust through seawater-rock alteration reactions involving the oxidation and hydration of glassy basalt.
Astrobiologists hypothesize that shallow water, not deep water, may have cradled the planet's first life; that the dark, carbon-poor depths offered little energy to emerging life. But the newfound abundance of seafloor microbes makes it theoretically possible that early life thrived - and maybe even began - on the seafloor. "Some might even favor the deep ocean for the emergence of life since it was a bastion of stability compared with the surface, which was constantly being blasted by comets and other objects," suggests study author and NAI member Katrina Edwards in the University of Southern California press release. For images and resources, see NSF's press page.
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5/27/2008
A new study from NAI's Montana State University Team appears in the current issue of the Journal of the American Chemical Society. The study probes the hydrogenase enzyme, a large, complex enzyme which plays a major role in anaerobic metabolism by creating molecular hydrogen. The research team produced a crystal structure of the enzyme to unprecedented resolution, revealing a new level of detail in the enzyme's active site, and providing clues about it's evolution. These results further our understanding of the transition from the abiotic (non-living) world to the biological world which may have been an early event in the development of life on Earth, and possibly a common feature of life elsewhere in the universe. |
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5/22/2008
A new study in the May 15th issue of Nature from NAI’s Carnegie Institution of Washington Team reveals that Europa’s poles may not have always been located in the same place. Using images from three NASA spacecraft, Voyager, Galileo, and New Horizons, the study mapped surface features on Europa and matched them with a pattern predicted if Europa had experienced an episode of ~80 degree true polar wander. This movement of the pole and subsequent change in rotation axis is only possible if Europa’s outer shell is decoupled from the core by a liquid layer, so the study also reinforces evidence for the presence of an ocean on Europa. |
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5/9/2008
Shawn D. Domagal-Goldman (NAI PSU team), J.F. Kasting (NAI PSU team), D. T. Johnson (NAI CIW team), and J. Farquhar (NAI CIW and UCLA teams) have just published an article Organic haze, glaciations and multiple sulfur isotopes in the Mid-Archean era in Earth and Planetary Science Letters. The team used sulfur isotope signatures within ancient sediments and a photochemical model of sulfur dioxide photolysis to interpret the evolution of the atmosphere over the first half of Earth’s history. |
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3/27/2008
Former NAI Postdoctoral Fellow Giovanna Tinetti is co-author on a groundbreaking paper in Nature detailing the observation of methane and water vapor in the atmosphere of the extrasolar planet HD 189733b. The team used the NASA Hubble Space Telescope to observe the transiting exoplanet, using the NICMOS camera to obtain a spectrophotometric time series. This result is a milestone in the search for life elsewhere in the Universe, most importantly because it demonstrates that we have the technology to identify these molecules in exoplanet atmospheres. |
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3/25/2008
Scientists from NAI’s Carnegie Institution of Washington Team have a new paper in Meteoritics and Planetary Science detailing their discovery of amino acids in two meteorites at concentrations ten times higher than levels previously measured in other similar meteorites. The result suggests that the early solar system was far richer in the organic building blocks of life than scientists had thought, and that fallout from space may have spiked Earth’s primordial broth. |
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3/6/2008
Researchers from NAI's University of Hawai'i Team used ground-based telescopes to observe the magnetic field of the planet hosting star tau Bootis, and found that its overall polarity has reversed direction since their observation one year prior. They report their findings in the Monthly Notices of the Royal Astronomical Society. This is the first time that a global magnetic polarity switch is observed in a star other than the Sun. |
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2/14/2008
Matt Pasek from NAI's University of Arizona Team recently published a paper in PNAS positing that the geochemistry of phosphorus on the early Earth was controlled by reduced oxidation state phosphorus compounds such as phosphite, rather than orthophosphate. This alternate view of early Earth phosphorus geochemistry provides an unexplored route to the formation of pertinent prebiotic phosphorus compounds, suggests a facile reaction pathway to condensed phosphates, and is consistent with the biochemical usage of reduced oxidation state phosphorus compounds in life today. |
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2/14/2008
New work from NAI's University of Hawai'i Team in Icarus indicates that astronomers will eventually be able to discriminate between extrasolar Earth-like planets with surface oceans and those without using the shape of phase light curves in the visible and near-IR spectrum. Their results suggest several new ways of directly identifying water on distant planets. |
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1/7/2008
A decade of planetary exploration, focusing on a “follow the water” approach, has yielded a tantalizing array of astrobiologically compelling targets. But the growing list of water-bearing planets and moons has also underscored the need to develop additional metrics for habitability. Research from within the NASA Astrobiology Institute is developing a “follow the energy” approach to complement “follow the water." The new issue of Astrobiology compiles several papers on this approach, guest-edited by Tori Hoehler from NAI's Ames Team. |
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1/7/2008
Researchers from NAI's Carnegie Institution of Washington Team have found the first indications of highly complex organic molecules in the disk of red dust surrounding a distant star. The eight-million-year-old star, known as HR 4796A, is inferred to be in the late stages of planet formation, suggesting that the basic building blocks of life may be common in planetary systems. The paper appears in the Astrophysical Journal Letters; a copy of the paper can be found here. |
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11/28/2007
Researchers from NAI's University of Hawai'i Team have a new paper in The Astronomical Journal describing a major survey of visual binaries toward the Orion Nebula Cluster. The team used images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope through an Hα filter. Among 781 stars that fulfill the criteria for membership in the Orion Nebula Cluster, the group found 78 multiple systems (75 binaries and 3 triples), of which 55 are new discoveries.
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11/14/2007
With support from NAI Teams at the Carnegie Institution of Washington and UC Berkeley, researchers at the American Type Culture Collection and their colleagues have a new paper in PLOS One describing a novel lineage of proteobacteria which are dominant in iron-rich hydrothermal vent sites on the Loihi Seamount near Hawai'i. They form a unique morphological structure which could serve as a fossil biomarker. |
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11/14/2007
Researchers from NAI's University of Hawai'i Team and their colleagues have a new paper in Geobiology reviewing recent work on the climatic, geochemical, and ecological events that preceded animal fossils, considering their portent for metazoan evolution. They also consider recent published research on the nature and chronology of the earliest fossil record of metazoans, and on the molecular-based analysis that yielded dates older than the last 35 million years of the Precambrian for the appearance of major animal groups. |
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10/11/2007
In this week's Science, astrobiologists from NAI's University of Hawai'i Team review the prospects for discovering smaller planets more like Earth, some of which may even have conditions suitable for life. Improved techniques and the ability to monitor fainter stars now enable astronomers to discover smaller planets, particularly planets orbiting much closer to their host star than the Earth is to the Sun. This review article is based on an NAI-supported session at the May, 2007 meeting of the American Astronomical Society. |
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10/11/2007
Researchers from NAI's Carnegie Institution of Washington Team have a paper in this week's Nature describing evidence that Earth's Mesoarchean atmosphere (3.2 and 2.8 Gya) possessed very low amounts oxygen. These findings contrast with prior claims that Earth's atmosphere underwent its first rise in oxygen during the Mesoarchean, and indicate that oxygen first rose above parts per million levels sometime between 2.45 and 2.4 billion years ago. |
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10/9/2007
NAI's Marine Biological Laboratory Team has a new paper in this week's Science detailing aspects of population structure for microbial communities at two neighboring hydrothermal vents. Using environmental DNA sequencing techniques, they found the two populations reflect the geochemical conditions of each vent. |
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9/28/2007
NAI's Astrobiology Drilling Program supported researchers in 2004 to obtain subsurface core samples from the Hamersley Basin in Western Australia. Those samples, representing the time just before the Great Oxidation Event, have been analyzed, and two research papers detailing the results (Anbar, et al. and Kaufman, et al.) appear in September 28, 2007 issue of Science. Both groups found unexpected, correlated changes that reveal the presence of small but significant amounts of O2 in the environment 2.5 billion years ago, ~50-100 milion years before the Great Oxidation Event, and a shift from lower O2 abundance prior to that time. |
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9/13/2007
Norbert Schorghofer of NAI's University of Hawai'i Team has a new paper in this week's Nature describing a climate model he developed which accounts for the advance and retreat of the subsurface martian ice layers. The model reveals forty major ice ages over the past five million years, and explains the present distribution of subsurface ice on Mars. His findings outline expectations of ice stratigraphy at the NASA Mars Phoenix Mission's landing site. |
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8/31/2007
Biomarkers in rocks prior to the rise in Earth's atmospheric oxygen 2.5 billion years ago show cyanobacteria released oxygen at the same levels as today. What was happening to that oxygen? A new paper in this week's Nature from NAI's Penn State Team proposes that the rise of atmospheric oxygen occurred because the predominant sink for oxygen—enhanced submarine volcanism—was abruptly and permanently diminished during the Archaean–Proterozoic transition by a shift from predominantly submarine volcanism to a mix of subaerial and submarine volcanism. |
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8/31/2007
NAI Postdoctoral Fellow Elise Furlan from NAI’s UCLA Team is co-author on a new paper in Nature this week reporting the development of a protoplanetary disk. Using NASA’s Spitzer Space Telescope, observations were made of water vapor within the emerging system’s natal cloud. Lead author Dan Watson of the University of Rochester said, "For the first time, we are seeing water being delivered to the region where planets will most likely form." |
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8/17/2007
A new paper in Nature this week from NAI's NASA Ames Research Center Team describes a new technique they've developed through which completely new enzymes can be evolved in the laboratory. The process does not require prior understanding of how the enzymes will work, but uses product formation as the sole selection criterion. |
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7/11/2007
An international team of researchers including members of NAI's Virtual Planetary Laboratory Team have, using NASA's Spitzer Space Telescope, detected the presence of water vapor on the hot jupiter HD 189733b. Published in this week's Nature, the study's primary author, Giovanna Tinetti, was a 2003 NAI Postdoctoral Fellow. |
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6/28/2007
Scientists from NAI's University of Arizona Team have studied the outflow of VY Canis Majoris, an oxygen-rich supergiant star. Thier results show that, against expectations, an old, oxygen-rich star can synthesize a chemically varied molecular cocktail. The study is published in this week's Nature, and a News and Views about the paper is also available. |
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6/18/2007
Scientists from NAI's IPTAI Team have a paper out in Geophysical Research Letters detailing a new mechanism for recent methane release on Mars. Their results show that increasing salinity can cause destabilization of subsurface methane hydrates, and that active thermal or pressure fluctuations are not required to account for the presence of methane in the atmosphere. |
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6/14/2007
Scientists from NAI's University of California, Berkeley Team have a new paper out in Nature outlining evidence for the presence of an ancient ocean on Mars. The study points to a large body of liquid water at the pole which could have shifted Mars' spin axis. This shift would have in turn deformed the shoreline of this ocean relative to the rest of the surface topography, in accordance with observations. |
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6/14/2007
Deep inside a flooded mine in Wisconsin, scientists from NAI’s University of California, Berkeley Team have discovered an environment in which bacteria emit proteins that sweep up metal nanoparticles into immobile clumps. Their finding may lead to innovative ways to remediate subsurface metal toxins, and have exciting implications for identifying biosignatures on Earth and other worlds. The research, published in the June 14th issue of Science, was done in collaboration with a team from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory. |
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6/7/2007
A new paper on the evolutionary relationships among New World tropical frogs was published online this week in PNAS. The authors, including members of the NAI Penn State Team, used DNA sequence and molecular clock analyses to further understand the frogs' origin as more likely by dispersal over water from South America, than via land connections with North and South America. |
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6/6/2007
Members of NAI's Michigan State University Alumni Team are part of an international team of scientists characterizing the microbial populations in Antarctic permafrost soils. Based on multiple samples, they describe the presence of diverse populations of both aerobic and anaerobic bacteria, cyanobacteria, green algae, yeasts, and fungi. Based on the documented ages of the permafrost regions—perhaps more than 5 million years old—these findings represent the oldest viable microorganisms discovered in permafrost on Earth. Their paper appears in the April issue of Astrobiology.
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5/2/2007
NAI scientists from the Carnegie Institution of Washington Team and their colleagues have a new paper in Geology outlining their process in resolving the mysterious identity of the Devonian fossil organism Prototaxities as a fungus. The team analyzed carbon isotopic ratios of the fossil relative to plants that lived in the same environment 400 million years ago. |
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4/18/2007
Members of NAI's Virtual Planetary Laboratory Alumni Team and their colleagues have a new paper in the current issue of Astrobiology. They present a critical discussion of M star properties that are relevant for the long- and short-term thermal, dynamical, geological, and environmental stability of conventional liquid water habitable zone (HZ) M star planets. |
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4/17/2007
NAI Postdoctoral Fellow Sean Raymond leads a team of authors from NAI's University of Colorado, Boulder, and University of Arizona Teams, and Virtual Planetary Laboratory and University of Washington Alumni Teams in a new publication in Astrobiology. They present analysis of water delivery and planetary habitability in 5 high-resolution simulations forming 15 terrestrial planets. Their results outline a new model for water delivery to terrestrial planets in dynamically calm systems, which may be very common in the Galaxy.
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4/11/2007
Differently colored plants may live on extra-solar planets, according to two new papers in the current issue of Astrobiology authored by members of NAI's Virtual Planetary Laboratory Alumni Team and their colleagues. They took previously simulated planetary atmospheric compositions for Earth-like planets orbiting various star types (including M stars), generated spectra, and found that photosynthetic pigments may peak in absorbance in the blue for some star types, and red-orange and near-infrared for others. Their results also suggest that, under water, organisms would still be able to survive ultraviolet flares from young M stars and acquire adequate light for growth - which greatly increases the scope for habitability in these systems. |
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4/10/2007
Multidisciplinary work from members of NAI's SETI Institute Team and a host of collaborators across the NAI re-examines what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid–surface–water habitable zone close to an M dwarf star. Their new paper, published in the current issue of Astrobiology, presents the summary conclusions of an interdisciplinary workshop sponsored by NAI and convened at the SETI Institute in 2005. |
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4/9/2007
New work from NAI NASA Ames Research Center Team members and their colleagues published recently in PNAS suggests that the cause for much of the extended red emission, or ERE, is due to closed-shell cationic polycyclic aromatic hydrocarbon, or PAH, dimers. Their work sheds light on the processes involved in carbonaceous dust evolution in the interstellar medium. |
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3/5/2007
NAI's Marine Biological Laboratory and Carnegie Institution of Washington Teams are contributing authors on a new paper in Earth and Planetary Science Letters presenting a new model for the evolution of Proterozoic deep seawater composition based on rare earth elements. Their data suggest transitional, suboxic conditions in the deep ocean (vs. sulfidic), which likely limited nutrient concentrations in seawater and, consequently, may have constrained biological evolution. |
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2/27/2007
New research from NAI's SETI Institute Team published online in Icarus today outlines the empirical range of salt concentrations permitted for Europa’s ocean. Solutions within the range imply high, near-saturation salt concentrations and require a Europan ice shell of less than 15 km thick, with a best fit at 4 km ice thickness. The paper examines the implications for subsurface habitability. |
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2/26/2007
Researchers from NAI's Carnegie Institution of Washington and NASA Goddard Space Flight Center Teams have a new paper in Nature describing the infrared spectrum of exoplanet HD 209458b as obtained by the NASA Spitzer Space Telescope. Scientists from NAI's University of Arizona and Alumni Virtual Planetary Laboratory Teams are contributing authors on a similar paper in Astrophysical Journal Letters which details the spectrum of exoplanet HD 189733b. Both sets of results show relatively flat spectra, with no significant absorption by water or methane, in contrast with the predictions of most atmospheric models. One spectral feature of HD 209458b is attributed to silicate clouds. The Nature paper features the work of an NAI Summer Undergraduate Intern at the Goddard Center for Astrobiology. Both papers were the subject of a recent NASA News conference. |
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2/8/2007
Researchers from NAI's University of Colorado, Boulder Team recently reported in Earth and Planetary Science Letters their new biogeochemical model relating to the Great Oxidation Event. With ion microprobe data for individual sulfides from water-lain sedimentary units in the 2.45–2.22 Ga Huronian Supergroup, the team proposes a new model where enhanced weathering rates during interglacial thawing stimulated blooms of oxygenic photosynthesis, the demise of methane, and ultimately the irreversible rise in atmospheric oxygen between the first and second Huronian glaciations. The paper's lead author was also the recipient of an NAI Research Scholarship in 2004. |
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2/7/2007
A team of researchers including members of NAI's University of Colorado, Boulder Team have provided the first direct field evidence supporting the theory that high concentrations of greenhouse gases could have helped avoid global freezing on the early Earth. They analyzed iron carbonates from 3.75-3.8 billion year old rocks in northern Québec, and conclude that the atmosphere of early Earth contained high levels of CO2. Their paper appears in a recent issue of Earth and Planetary Science Letters. |
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12/21/2006
Scientists from NAI's University of California, Berkeley Team report in this week's Science on their use of shotgun sequencing to uncover three novel archea present in all biofilms growing in pH 0.5 to 1.5 solutions within the Richmond Mine, California. Their results inform the problem of characterizing microbial communities and lineages which are difficult to cultivate. |
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12/21/2006
Using atmospheric chemical models of a Snowball Earth, scientists from NAI's Alumni Virtual Planetary Laboratory Team show that, during long and severe glacial intervals, a weak hydrological cycle coupled with photochemical reactions involving water vapor would give rise to the sustained production of hydrogen peroxide. The peroxide, upon release from melting ice into the oceans and atmosphere at the end of the snowball event, could mediate global oxidation events. Their results are published in the December 12th issue of PNAS. |
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12/14/2006
Researchers from NAI's Carnegie Institution of Washington Team have published in Science their findings of a novel archaeon who's ability to fix nitrogen at 92 degrees Celcius has officially increased the upper limit of biological nitrogen fixation by 28 degrees Celcius. The hyperthermophilic methanogen was isolated from a hydrothermal vent. Thier findings could reveal a broader range of conditions for life in the subseafloor biosphere. |
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12/14/2006
A special issue of Science (Dec 15) includes several papers reporting on various aspects of Stardust sample analysis including an organics survey, isotopic and elemental compositions, mineralogy and petrology, and infrared spectroscopy. Many NAI researchers contributed to this comprehensive analytical campaign, including members of NAI's Teams at the Carnegie Institution of Washington, NASA's Ames Research Center and Goddard Space Flight Center, and NAI's Alumni Team at the University of Washington. |
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12/11/2006
An international team of researchers including NAI Postdoctoral Fellow Evgenya Shkolnik of the University of Hawai'i Team publish their observation in this month's Royal Astronomical Society Letters of a magnetic field at the surface of star Tau Bootis, which is orbited by a giant planet every three days. The magnetic field's intensity is similar to that of the Sun, but the star and the planet are tidally locked, possibly producing the observed magnetic knots. |
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11/27/2006
The December 2006 issue of Geobiology is a collection of papers focusing on the history of Earth's biogeochemistry, from the earliest sedimentary rocks in Greenland to the late Proterozoic. The rise of atmospheric oxygen provides a thematic link. The papers in this issue, edited by David Catling and Roger Buick of NAI's University of Washington Alumni Team, grew out of a session of the Earth System Processes 2 conference in Calgary, Canada, 8–11 August 2005, sponsored by the NAI. |
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11/20/2006
Robert Hazen, from NAI's Carnegie Institution of Washington Team, published his 2005 Presidential Address to the Mineralogical Society of America in this month's American Mineralogist. The address reviews the role of mineral surfaces on the self-assembly of lipids, the polymerization of amino acids and nucleic acids, and the selective adsorption of organic species, including chiral molecules, onto mineral surfaces. |
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11/7/2006
Researchers from NAI's Unviersity of Colorado, Boulder and University of Arizona Teams have published a new study in PNAS this week about the atmospheres of both present day Titan and early Earth. For Titan, their experiments modeled conditions measured by the Huygens probe from NASA's Cassini mission, and CO2 was added to model the early Earth conditions. They conclude that organize haze can form over a wide range of methane and carbon dioxide concentrations. |
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10/25/2006
Peter Ward from NAI's Alumni Team at the University of Washington and his collaborators have a new paper out in PNAS this week providing supportive evidence for Romer's Gap. Their results link this gap in vertebrate terrestrialization with a low atmospheric oxygen interval. This paper supports Ward's new book on the evolution of effective respiratory systems, entitled "Out of Thin Air." |
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10/20/2006
In this week's Science, researchers from NAI's Indiana, Princeton, Tennessee Astrobiology Initiative (IPTAI) and Carnegie Institution of Washington Teams report that they have found an extant microbial biome at 2.8km depth in a South African mine. Analyses showed thermophilic sulfate reducers existing "with no apparent reliance on photosynthetically derived substrates." |
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10/17/2006
Researchers from NAI's UCLA, Carnegie Institution of Washington, and NASA Goddard Space Flight Center Teams published this week in Science Express what may well be the first "Interstellar Weather Report." Focusing on the innermost planet orbiting the star Upsilon Andromeda b, a hot Jupiter, the team used NASA's Spitzer Space Telescope to make measurements indicating that the temperature variation between the planets light and dark sides is 2,550 degrees Fahrenheit. |
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10/17/2006
A new study on carbon isotopes in sedimentary rocks from Western Australia by researchers from NAI's Penn State and Carnegie Institution of Washington Teams supports the idea that small, shallow pools of water containing photosynthetic microbes existed on the early Earth ~ 2.72 Gya, about 300 million years before the rise of oxygen in the atmosphere. Their findings suggest a "global-scale expansion" of these habitats, and a progression away from anaerobic ecosystems and toward photosynthetic communities before the oxygenation of the atmosphere. This work was published in the early edition of this week's PNAS. |
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10/4/2006
Members of the Former University of Rhode Island Team, have published their latest findings on the production of ethane and propane in the deep subsurface in this week'sPNAS.
The work stems from cores drilled on Leg 201 of the Ocean Drilling Program, February-March 2002. The Ocean Drilling Program is succeeded by the Integrated Ocean Drilling Program which concluded it's "Exploring Subseafloor Life" workshop this week in Vancouver. |
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9/8/2006
Collaborators from NAI's Teams at NASA Goddard Space Flight Center, University of Colorado, Boulder, and Penn State as well as the former Virtual Planetary Lab Team have a paper this week in Science discussing the possible formation of "Exotic Earths." Their models have simulated terrestrial planet growth during and after inward giant planet migration. Their results cause them to speculate that more than a third of the known systems of giant planets may harbor Earth-like planets. |
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8/24/2006
Most geologists agree that Earth's atmosphere was oxygen-free until 2.4 billion years ago. But the latest research from NAI's Pennsylvania State University team provides new evidence for alternative viewpoints. Ohmoto et al have published their latest results in this week's Nature. Ohmoto's team took samples from western Australia as a part of NAI's Astrobiology Drilling Program.
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8/18/2006
Pennsylvania State University Team members, Matt Hurtgen and colleagues, have just published a new paper in Earth and Planetary Science Letters on continental glaciers in the Neoproterozoic. |
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8/1/2006
NAI PI of the Marine Biological Laboratory Team, Mitch Sogin, and his team have published a new paper in PNAS documenting astonishing new findings of microbial diversity in the deep sea. The findings are the result of a new DNA technique called "454 tag sequencing."
Image courtesy of Micro*scope |
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7/25/2006
Scientists from NAI's UCLA and University of Colorado, Boulder Teams recently published their new geologic and geochemical analysis of the ancient rocks on Akilia Island in West Greenland which were the subject of a controversial Nature paper ten years ago. This new study includes a thorough geologic map of the area, and, using the ion-microprobe to analyze carbon inclusions in the rock, outlines a carbon isotopic ratio indicative of life's signature. Their work appears in the current issue of the American Journal of Science. |
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7/25/2006
Researchers from NAI's University of Washington, University of Colorado, Boulder, and Virtual Planetary Laboratory Teams have developed models testing planet formation in four known systems, 55 Cancri, HD 38529, HD 37124 and HD 74156. Placing Mars to Moon-sized planet embryos between giant planets and allowing them to evolve for 100 million years, they found terrestrial planets formed readily in 55 Cancri, sometimes with substantial water and orbits in the system's habitable zone. They found HD 38529 is likely to support an asteroid belt and Mars-sized or smaller bodies but no notable terrestrial planets. No planets formed in HD 37124 and HD 74156. The paper was published in a recent issue of The Astrophysical Journal. |
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7/5/2006
Researchers from NAI's University of Rhode Island Team and their colleagues have studied the use of phosphorus vs. sulfur in the membrane lipid sythesis pathways of organisms resident in the ocean's subtropical gyres. Their data show that the dominant organism in the phytoplankton, a cyanobacterium, has evolved a "sulfur-for-phosphorus" strategy; producing a membrane lipid containing sulfate and sugar instead of phosphate. This adaptation may have been a major event in Earth's early history when the relative availability of sulfate and phosphate was different than in today's oceans. Their paper appears in the June 6th issue of PNAS. |
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7/5/2006
NAI's Virtual Planetary Laboratory Team have explored the possibility of detecting exovegetation on terrestrial planets orbiting M stars. They estimated the red-shift of this surface feature using leaf optical property spectra with a three photon photosynthetic scheme. The authors have produced a model wherein a pigment-derived surface signature such as exovegetation could be detected, but would be dependent upon the extent of the vegetation on the surface, cloud cover, and viewing angle. Their paper is in the current issue of The Astrophysical Journal. |
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6/19/2006
Researchers from NAI's NASA Goddard Space Flight Center Team and their colleagues publish their analysis of two meteorites in the current issue of Meteoritics and Planetary Science. Their study revealed a suite of amino acids present in the meteorites that are not present in the Antarctic ice on which they were found. |
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6/19/2006
Andrey Bekker of NAI's Carnegie Institution of Washington Team and his colleagues have an article in press for Precambrian Research which details the carbon isotope record for the carbonate platform in the Great Lakes area. Observed carbon isotope values from the Lake Superior area may correspond to those from Griqualand West Basin, South Africa, supporting the notion of three global glaciations in the Paleoproterozoic Era. |
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6/14/2006
Using NASA's FUSE spacecraft, scientists from NAI's Carnegie Institution of Washington Team have discovered abundant amounts of carbon gas in a dusty disk surrounding the young star Beta Pictoris. While planets may have already formed, the prevalence of carbon gas in the disk indicates that the planets could be carbon-rich worlds of graphite and methane, potentially resembling the early conditions of our own Solar System. The authors suggest that either carbon-rich asteroids or comets, unlike any in our own solar system, have vaporized, or that bodies outgassing carbon-bearing species such as methane are responsible for the observation. Their work is published in this week's Nature. |
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6/14/2006
Roger Buick from NAI's University of Washington Team and his colleagues report in the current issue of Geology their analysis of oil-bearing fluid inclusions in 2.45 billion year old rocks from Canada. They assert that the oil is derived from an overlying formation, becoming trapped in the host rock before 2.2 billion years ago - prior to the Great Oxidation Event. Abundant biomarkers for cyanobacteria and eukaryotes were identified in the study, suggesting that aqueous environments at the time had become sufficiently oxygenated for sterol biosynthesis to occur, and implying that organisms had the ability to survive "snowball Earth" glaciations. |
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6/7/2006
The cover of this week's Nature belongs to Abigail Allwood of the Australian Centre for Astrobiology, one of NAI's International Partners. She and her colleagues put forward the latest research on the ancient rocks of the Pilbara Craton in Western Australia, which points to evidence of life on Earth 3.43 billion years ago. Their description of a shallow marine environment, and identification of seven stromatolite morphotypes makes a strong argument for early life. NAI supported Allwood's work with a 2005 NAI Research Scholarship. |
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6/7/2006
Alan Boss of NAI's Carnegie Institution of Washington Team published in the current issue of the Astrophysical Journal a new look at the origin of super-Earths orbiting M dwarf stars. The core accretion mechanism of giant planet formation has been used to explain the presence of these planets. Boss' new work shows they could also have been formed by the disk instability mechanism. |
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6/6/2006
Researchers from NAI's NASA Ames Research Center and University of Colorado, Boulder Teams published in the current issue of Astrobiology their study of the petrology and mineral chemistry of a cold spring in Northern California. They propose that the serpentinization process can provide a source of energy for chemosynthetic organisms, and outline criteria to aid in the identification of serpentinizing terranes on Mars. |
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5/31/2006
An alternative theory for the origin and evolution of life is proposed by scientists from NAI's Pennsylvania State University Team in the current issue of Molecular Biology and Evolution. The theory, centering on the concept that an energy-conservation pathway was the major force which powered and directed the early evolution of the cell, provides insight into the evolution of the microbial production of methane. |
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5/31/2006
Researchers from NAI's Indiana Princeton Tennessee Astrobiology Initiative Team published their theory on the origin of the detected atmospheric methane on Mars in the current issue of Astrobiology. Measurements of deep fracture water samples from South Africa led to a model which distinguishes between abiogenic and microbial methane sources based upon their isotopic composition, and couples microbial methane production to molecular hydrogen generation by water radiolysis. The authors also propose an instrument for future missions to Mars which, with measurements over time, could distinguish mechanisms for methane emissions. |
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5/18/2006
Researchers at NAI's University of Colorado, Boulder and Marine Biological Laboratory Team published their analysis of biodiversity in hypersaline microbial mats in a recent issue of Applied and Environmental Microbiology. Bacteria dominated the mat in unprecedented diversity representing 752 species, including 15 novel candidate phyla. |
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5/18/2006
Researchers from NAI's Pennsylvania State University Team published their functional and phylogenetic analysis of protein WrbA function this week in The Journal of Bacteriology. Comparing 30 sequences including that of Archaeoglobus fulgidus, a hyperthermophilic archeabacterium, this study demonstrates the ability for this enzyme to protect against oxidative stress through quinone oxidoreductase activity. |
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5/9/2006
Researchers at NAI's Carnegie Institution of Washington Team published this week in Science their new study of the interstellar chemistry record in both meteorites and interplanetary dust particles. They show that isotopic compositions in meteories meet and exceed those in found in IDP's, demonstrating the capability of both to preserve primitive organics. |
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5/3/2006
Scientists on NAI's Pennsylvania State University Team published new findings recently in Nature demonstrating a single early origin of the venom system in snakes and lizards. Their molecular biology and toxinological analyses show that the snakes, iguanians and anguimorphs form a single clade, pointing toward the proposed common origin. |
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4/19/2006
A new study published by former NAI Team Arizona State University members documents the extensive microbial biodiversity of one Earth's rare ecosystems. "An endangered oasis of aquatic microbioal biodiversity in the Chihuahuan desert" is available in PNAS . |
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4/18/2006
Former NAI Principal Investigator, Andy Knoll of Harvard University, and colleagues discuss the evolution of cyanobacteria in their new paper, "The evolutionary diversification of cyanobacteria: Molecular-phylogenetic and paleontological perspectives" in the April 4th issue of PNAS. The evolutionary timeline has implications for the rise of atmospheric oxygen on Earth.
Image courtesy of Micro*scope |
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4/13/2006
Researchers from NAI's University of California, Los Angeles Team have pioneered a new imaging technique which allows them to non-destructively produce 3D images of ancient fossils. The technique, combining confocal microscopy and Raman spectroscopy, could be used on samples returned from Mars by future NASA missions. Their work on 650 million year old fossils from Kazakhstan is published in the February, 2006 issue of Astrobiology. |
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4/7/2006
To assess the detectability of planetary characteristics in disk-averaged spectra, the NAI Virtual Planetary Laboratory Team has developed a spatially and spectrally resolved model of the Earth. Using infrared observations of the Earth taken by existing instruments orbiting Mars, and ground-based observations of earthshine, the model has been validated, and indicates that several atmospheric species can be identified. Models such as this one will help analyze disk averaged spectra as returned from upcoming NASA and ESA extra-solar planet detection and characterization missions. They published their results in the February issue of Astrobiology. |
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2/28/2006
A new paper this week in PNAS highlights a collaboration between NAI Lead Teams at Penn State, University of Rhode Island, UCLA, and the Marine Biological Laboratory. Their research reveals that heterotrophic Archea dominate the scene in a variety of biogeochemically distinct sedimentary regions, and may constitute a significant portion of the prokaryotic biomass in Earth's subsurface. Ecosystem-level carbon budgets suggest that community turnover times are on the order of 100-2,000 years. |
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2/22/2006
In a new study published in this week's PNAS, researchers from NAI's University of Rhode Island Lead Team report the vertical and geographical distribution of microbes in deeply buried marine sediments of the Pacific Ocean Margin. Sediment cores from the Peru and Cascadia Margins were obtained, and thousands of clones were studied to describe the nature of the biomass in areas with and without methane hydrates. The data suggest that prokaryotic communities from methane hydrate-bearing sediment cores are distinct from those in hydrate-free cores. This study is an important step in understanding the role of biology in Earth's essential biogeochemical processes. |
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1/30/2006
A review article in Nature this week from scientists on NAI's University of California, Berkeley Lead Team examines the idea of the influence of life on topography. The authors call for a need to explore how small scale biotic processes can influence an entire landscape, and whether the resulting topography is distinct. |
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1/12/2006
Rocco Mancinelli, PI of NAI's SETI Institute Lead Team, and member of NAI's NASA Ames Research Center Lead Team joined researchers from KSC and Ames, as well as NAI's Former Director, Barry Blumberg, in studying populations of C. Elegans which survived the atmospheric breakup of STS-107 during it's fatal re-entry. Their results are published in Astrobiology. Five canisters were recovered, and live animals were observed in four of them. This demonstrates not only the ability of the culture medium to support the organisms during spaceflight, but also the ability of the animals to survive a relatively unprotected re-entry into Earth's atmosphere. This study has implications for planetary protection and the interplanetary transfer of life. |
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1/12/2006
NAI's Virtual Planetary Laboratory Lead Team has published new findings from their Lab about the observable, biosignature gases of theoretical planets orbiting M-Dwarf stars in this month's Astrobiology. Their outcomes are positive for designating M-Dwarfs a viable target for future observations involving the search for life. |
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12/21/2005
Tom McCollom of NAI's University of Colorado Lead Team and his co-author Brian Hynek published the details of their alternative model today in Nature. The scenario does not require prolonged interaction with a standing body of surface water, and describes an environment less favorable to biological activity on Mars. |
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12/19/2005
Researchers from NAI's Pennsylvania State University Lead Team and their colleagues at Arizona State University published this week in PNAS their research constraining the divergence of humans and chimpanzees. Using the largest data set yet and improved computational methods for the molecular clock calculations, the study narrows the gap from between 3 and 13 million years ago to between 5 and 7 million years ago. |
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12/16/2005
NAI Affiliate Members at the Centro de Astrobiologia, and others have one of eight research articles focusing on Opportunity in this month's Earth and Planetary Science Letters. The paper explores the relationship between Meridiani and Rio Tinto, specifically how studying the river can help facilitate an understanding of Meridiani mineral precipitation and diagenesis, as well as astrobiological implications. |
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12/7/2005
Researchers from NAI's Carnegie Institution of Washington Lead Team published a study in this week's Science using high-precision measurements of a rare sulfur isotope, 33S, to establish that microbial sulfur disproportionation was in place almost half a billion years earlier than previously thought. This could imply that Earth's surface may have become progressively more oxygenated during the middle Proterozoic. |
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11/29/2005
Lee Kump of NAI's Pennsylvania State University Lead Team is co-author on a new paper in GSA Today examining the rise of atmospheric oxygen at the Archean-Proterozoic transition, 2.5-2.0 billion years ago. The team of international researchers studied sedimentary and volcanic rocks from the Fennoscandian Shield, which provides a fairly complete record of the hallmark events of that transition. |
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11/28/2005
Researchers from NAI's Pennsylvania State University Lead Team have conducted the most comprehensive analysis ever performed of the genetic relationships among all the major groups of snakes, lizards and other scaly reptiles. Their paper in C. R. Biologies explains the radical reorganization of this family tree, and the importance to astrobiology. |
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10/20/2005
Scientists from NAI's University of Arizona Lead Team have used the NASA Spitzer Space Telescope to observe the very beginnings of what might become planets around brown dwarfs. They publish their results this week in Science. |
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10/17/2005
A new paper in Earth and Planetary Science Letters from NAI's Carnegie Institution of Washington Lead Team and NAI's International Partner, the Australian Centre for Astrobiology, explores environmental changes during the rise of atmospheric oxygen and the relationship between tectonics, atmospheric oxygen, and climatic changes. |
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10/13/2005
Scientists from NAI's University of Arizona and University of Washington Lead Teams recently published a paper in Science concerning this history of the Solar System. Their paper looks at differences in the size distrubutions of asteroid populations during and after the heavy bombardment period ~ 3.8 billion years ago. |
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10/12/2005
David Des Marais from NAI's NASA Ames Research Center Lead Team recently published a News and Views article in Nature. In it, he discusses a microbial "footprint" which bolsters geological data explaining the long term rise in Earth's oxygen levels two billion years ago. |
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9/27/2005
Christopher Chyba and Kevin Hand of the NAI's SETI Institute Lead Team have just published this article in the Annual Reviews of Astronomy and Astrophysics (ARAA). It reviews the habitability of the Galaxy in general and of planets and moons in particular, and summarizes current controversies in origins-of-life research and in evidence for the earliest life on Earth. It critiques certain ?rare Earth? and ?anthropic? arguments, and considers four approaches to deciding whether intelligent life exists elsewhere in the Galaxy. It concludes that astrobiology must also speak to the future of human civilization. |
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9/27/2005
Investigators from NAI's UCLA and Carnegie Institution of Washington Lead Teams observed dust orbiting an old, relatively dead star, GD 362, and published their results in the Astrophysical Journal this month. This enigmatic observation could form the basis for predictions about the end of our own solar system. |
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8/17/2005
In this month's issue of Astrobiology, members of NAI's Virtual Planetary Laboratory Team published a study using their model of a Mars-like planet to ascertain the detectability of a planet’s surface and atmospheric properties from disk-averaged spectra. |
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8/17/2005
Members of NAI's University of Colorado Team published a study of the composition and structure of the Shark Bay stromatolites in this month's Applied and Environmental Microbiology. Their rRNA studies revealed the most abundant sequences representing novel proteobacteria, with a surprising less than 5% representing cyanobacteria. |
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8/5/2005
Amos Banin from NAI's SETI Institute Team discusses the state of knowledge about the Martian soil in this week's Science "Perspectives." He looks specifically at information gained from past missions, and the role water processing may have played in soil formation. |
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7/20/2005
Astronomers from NAI's Lead Teams at UCLA and the Carnegie Institution of Washington describe in this week's issue of Nature their observations of large quantities of warm dust debris surrounding a Sun-like star some 300 light years from Earth. The dust is orbiting close to the star, and is similar in composition to dust in the Solar System. The composition and quantity of the dust may indicate massive and/or frequent collisions of large objects, perhaps similar to the theorized impactor that struck Earth to form the Moon. |
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7/19/2005
Members of NAI's UCLA Lead Team published a paper in this month's Geophysical Research Letters describing how hydrothermal fluid processes driven by a small subsurface magmatic intrusion can produce methane on Mars. |
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7/8/2005
A recent Nature paper from Jim Lyons and Ed Young of NAI's UCLA Lead Team postulates a cause for oxygen isotope anomalies in meteorites that overthrows a long accepted explanation. They propose CO photodissociation due to a far ultraviolet flux caused by a nearby O or B star as a mechanism to produce the isotope fractionation that is consistent with the anomalies observed in the meteorites. The postulated presence of a nearby second star (within one parsec) means statistically that the forming Solar System was probably embedded in a cluster of ~200 stars. |
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6/15/2005
Andrey Bekker, once with NAI's former Harvard Lead Team and now part of NAI's Carnegie Institution of Washington Lead Team, led a study in this month's Precambrian Research that for the first time documents chemostratigraphy and correlates Early Paleoproterozoic post-glacial carbonates of North America and South Africa. |
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6/9/2005
New studies from NAI's University of Colorado team published in the February 15, 2005 issue of PNAS implicate the oxidation of molecular hydrogren as the source of energy for primary productivity in high temperature microbial ecosystems in Yellowstone. |
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6/9/2005
Charles Marshall of NAI's former Harvard University team published in this week's Science his commentary on what he calls NAI Principal Investigator Peter Ward's "groundbreaking" paper from January 2005. The comments are accompanied by a response from Ward et al. |
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5/16/2005
NAI scientists on the University of California, Berkeley team describe, in a recent issue of Icarus, how meteoritic impacts on Mars may have caused Earth-like saturated soil liquefaction and potentially enabled violent groundwater eruption. Enough water, they say, could have been erupted to produce floods and outflow channels. |
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5/16/2005
NAI scientists on the Penn State and University of Colorado teams published recently in Geology their studies showing that increases in the level of hydrogen sulfide in the deep ocean during oceanic anoxic periods in Earth's history could cause elevated H2S levels in shallower waters and in the atmosphere. This may have caused, they propose, destruction of the ozone shield and an increase in atmospheric methane, and may have helped spell the end for life at several extinction events. |
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5/9/2005
NAI's Mark Harrison of the UCLA team co-authored a study published
in this week's Science describing a titanium thermometer technique used to
measure the temperature at which ancient zircons from the Jack Hills in
Western Australia formed. The results paint a mild picture of the Hadean,
complete with an atmosphere and liquid water. |
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5/9/2005
Members of NAI's UC Berkeley team, led by Jill Banfield, published this week in Sciencexpress their study of the gene expression and protein complement
of a microbial biofilm community living in a natural acid mine drainage at
Iron Mountain in Northern California. The studies were done on
non-cultivated, natural samples, and proteins involved in protein refolding
and response to oxidative stress appeared to be highly expressed. |
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5/1/2005
NAI's Ben Zuckerman of the UCLA team told UCLA, "The two objects - the giant planet and the young brown dwarf - are moving together; we have observed them for a year, and the new images essentially confirm our 2004 finding." The international team recently published their discovery in Astronomy and Astrophysics. Team lead Gael Chauvin of the European Southern Observatory declares this to be the first planet outside our Solar System ever to be imaged. |
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4/25/2005
This week in Nature, members of NAI's University of Colorado, Boulder team published their description of an extremely acidic, endolithic, microbial community inhabiting the pore spaces between rocks Yellowstone National Park's Norris Geyser Basin. The community includes mainly photosynthetic algae and previously unknown Mycobacterium species. |
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4/25/2005
Scientists and theorists from NAI's International Affiliate Member, The Australian Centre for Astrobiology, recently published a "hypothesis paper" in Astrobiology discussing the possibility of life emerging on Earth more than once. |
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4/14/2005
This week, NAI Principal Investigator Peter Ward published a follow on to his January Science paper which described a potential cause for the extinction events on the P/T boundary: "atmospheric warming because of greenhouse gases triggered by erupting volcanoes." This new paper, "Hypoxia, Global Warming, and Terrestrial Late Permian Extinctions," further elucidates this story; its focus is on characterizing environmental degradation approaching and succeeding the "final catastrophe." |
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4/7/2005
NAI researchers on the University of Colorado Team published a new paper this week in ScienceExpress describing an increased quantity of hydrogen in Earth's early atmosphere due to a slower escape rate. In contrast to the view that the early atmosphere was oxidizing, this work implies a more favorable "climate" for the production of pre-biotic organic compounds like amino acids, and ultimately, life. |
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3/28/2005
An international collaboration including scientists from NAI's International Partner, Groupement de Recherche en Exobiologie (GDR Exobio), published recently in Astrophysics their new ideas about the temporal evolution of the circumstellar habitable zone. They describe the possibility of an icy planet in orbit around a star becoming "revived," and potentially habitable as the star leaves its main sequence. GDR Exobio collaborator Bruno Lopez of the Observatoire de la Cote d'Azur told NASA, "Our result indicates that searches for life-giving worlds outside our Solar System should include planets around old stars." |
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