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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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