Observations of gamma-ray burst reveal surprising ingredients of early galaxies

ScienceDaily (Nov. 2, 2011) — An international team of astronomers led by the Max Planck Institute for Extraterrestrial Physics has used the brief but brilliant light of a distant gamma-ray burst as a probe to study the make-up of very distant galaxies. Surprisingly the new observations revealed two galaxies in the young Universe that are richer in the heavier chemical elements than the Sun. The two galaxies may be in the process of merging. Such events in the early Universe will drive the formation of many new stars and may be the trigger for gamma-ray bursts.

Gamma-ray bursts are the brightest explosions in the Universe. They are first spotted by orbiting observatories that detect the initial short burst of gamma rays. After their positions have been pinned down, they are then immediately studied using large ground-based telescopes that can detect the visible-light and infrared afterglows that the bursts emit over the succeeding hours and days. One such burst, called GRB 090323, was first spotted by the NASA Fermi Gamma-ray Space Telescope. Very soon afterwards it was picked up by the X-ray detector on NASA's Swift satellite and with the GROND system at the MPG/ESO 2.2-metre telescope in Chile. From the GROND observations, the astronomers estimated the minimum rate of star formation, which has to be several times higher than the one in our Galaxy. They could, however, only determine a minimum value because the detected emission could be heavily affected (i.e. absorbed) by the presence of dust in the galaxies. The real rate of star formation, once the (unknown) dust absorption has been taken into account, could easily be 50 times higher than in the Milky Way.

The burst was also studied in great detail using ESO's Very Large Telescope (VLT) just one day after it exploded. These observations show that the brilliant light from the gamma-ray burst had passed through its own host galaxy and another galaxy nearby. These galaxies are being seen as they were about 12 billion years ago. Such distant galaxies are very rarely caught in the glare of a gamma-ray burst.

"When we studied the light from this gamma-ray burst we didn't know what we might find. It was a surprise that the cool gas in these two galaxies in the early Universe proved to have such an unexpected chemical make-up," explains Sandra Savaglio (Max-Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the paper describing the new results. "These galaxies have more heavy elements than have ever been seen in a galaxy so early in the evolution of the Universe. We didn't expect the Universe to be so mature, so chemically evolved, so early on."

As light from the gamma-ray burst passed through the galaxies, the gas there acted like a filter, and absorbed some of the light from the gamma-ray burst at certain wavelengths. Without the gamma-ray burst these faint galaxies would be invisible. By carefully analysing the tell-tale fingerprints from different chemical elements the team was able to work out the composition of the cool gas in these very distant galaxies, and in particular how rich they were in heavy elements.

It is expected that galaxies in the young Universe will be found to contain smaller amounts of heavier elements than galaxies at the present day, such as the Milky Way. The heavier elements are produced during the lives and deaths of generations of stars, gradually enriching the gas in the galaxies. Astronomers can use the chemical enrichment in galaxies to indicate how far they are through their lives. But the new observations, surprisingly, revealed that some galaxies were already very rich in heavy elements less than two billion years after the Big Bang. Something unthinkable until recently.

The newly discovered pair of young galaxies must be forming new stars at a tremendous rate, to enrich the cool gas so strongly and quickly. As the two galaxies are close to each other they may be in the process of merging, which would also provoke star formation when the gas clouds collide. The new results also support the idea that gamma-ray bursts may be associated with vigorous massive star formation.

Energetic star formation in galaxies like these might have ceased early on in the history of the Universe. Twelve billion years later, at the present time, the remains of such galaxies would contain a large number of stellar remnants such as black holes and cool dwarf stars, forming a hard to detect population of "dead galaxies," just faint shadows of how they were in their brilliant youths. Finding such corpses in the present day would be a challenge.

"We were very lucky to observe GRB 090323 when it was still sufficiently bright, so that it was possible to obtain spectacularly detailed observations with the VLT. Gamma-ray bursts only stay bright for a very short time and getting good quality data is very hard. We hope to observe these galaxies again in the future when we have much more sensitive instruments, they would make perfect targets for the E-ELT," concludes Savaglio.

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Journal Reference:

S. Savaglio et al. Super-solar Metal Abundances in Two Galaxies at z~3.57 revealed by the GRB090323 Afterglow Spectrum. Monthly Notices of the Royal Astronomical Society, 2011

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Clearing the 'cosmic fog' of the early universe: Massive stars may be responsible

ScienceDaily (Oct. 13, 2011) — The space between the galaxies wasn't always transparent. In the earliest times, it was an opaque, dense fog. How it cleared is an important question in astronomy. New observational evidence from the University of Michigan shows how high energy light from massive stars could have been responsible.

Astronomers believed that early star-forming galaxies could have provided enough of the right kind of radiation to evaporate the fog, or turn the neutral hydrogen intergalactic medium into the charged hydrogen plasma that remains today. But they couldn't figure out how that radiation could escape a galaxy. Until now.

Jordan Zastrow, a doctoral astronomy student, and Sally Oey, a U-M astronomy professor, observed and imaged the relatively nearby NGC 5253, a dwarf starburst galaxy in the southern constellation Centaurus. Starburst galaxies, as their name implies, are undergoing a burst of intense star formation. While rare today, scientists believe they were very common in the early universe.

The researchers used special filters to see where and how the galaxy's extreme ultraviolet radiation, or UV light, was interacting with nearby gas. They found that the UV light is, indeed, evaporating gas in the interstellar medium. And it is doing so along a narrow cone emanating from the galaxy.

A paper on their work is published Oct. 12 in Astrophysical Journal Letters.

"We are not directly seeing the ultraviolet light. We are seeing its signature in the gas around the galaxy," Zastrow said.

In starburst galaxies, a superwind from these massive stars can clear a passageway through the gas in the galaxy, allowing the radiation to escape, the researchers said.

The shape of the cone they observed could help explain why similar processes in other galaxies have been difficult to detect.

"This feature is relatively narrow. The opening that is letting the UV light out is small, which makes this light challenging to detect. We can think of it as a lighthouse. If the lamp is pointed toward you, you can see the light. If it's pointed away from you, you can't see it," Zastrow said. "We believe the orientation of the galaxy is important as to whether we can detect escaping UV radiation."

The findings could help astronomers understand how the earliest galaxies affected the universe around them.

Also contributing were researchers from the University of Maryland, MIT's Kavli Institute for Astrophysics and Space Research, and the University of California, Berkeley. The research is funded by the National Science Foundation. Observations were conducted with the Magellan Telescopes at Las Campanas Observatory in Chile.

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Jordan Zastrow, M. S. Oey, Sylvain Veilleux, Michael McDonald, Crystal L. Martin. An ionization cone in the dwarf starburst galaxy NGC 5253. The Astrophysical Journal, 2011; 741 (1): L17 DOI: 10.1088/2041-8205/741/1/L17

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NASA's Chandra finds massive black holes common in early universe

ScienceDaily (June 15, 2011) — Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.

By pointing Chandra at a patch of sky for more than six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million to 950 million years old.

"Until now, we had no idea what the black holes in these early galaxies were doing, or if they even existed," said Ezequiel Treister of the University of Hawaii, lead author of the study appearing in the June 16 issue of the journal Nature. "Now we know they are there, and they are growing like gangbusters."

The super-sized growth means that the black holes in the CDFS are less extreme versions of quasars -- very luminous, rare objects powered by material falling onto supermassive black holes. However, the sources in the CDFS are about a hundred times fainter and the black holes are about a thousand times less massive than the ones in quasars.

The observations found that between 30 and 100 percent of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the small observed field to the full sky, there are at least 30 million supermassive black holes in the early universe. This is a factor of 10,000 larger than the estimated number of quasars in the early universe.

"It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski of Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later."

A population of young black holes in the early universe had been predicted, but not yet observed. Detailed calculations show that the total amount of black hole growth observed by this team is about a hundred times higher than recent estimates.

Because these black holes are nearly all enshrouded in thick clouds of gas and dust, optical telescopes frequently cannot detect them. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

Physicists studying black holes want to know more how the first supermassive black holes were formed and how they grow. Although evidence for parallel growth of black holes and galaxies has been established at closer distances, the new Chandra results show that this connection starts earlier than previously thought, perhaps right from the origin of both.

"Most astronomers think in the present-day universe, black holes and galaxies are somehow symbiotic in how they grow," said Priya Natarajan, a co-author from Yale University. "We have shown that this codependent relationship has existed from very early times."

It has been suggested that early black holes would play an important role in clearing away the cosmic "fog" of neutral, or uncharged, hydrogen that pervaded the early universe when temperatures cooled down after the Big Bang. However, the Chandra study shows that blankets of dust and gas stop ultraviolet radiation generated by the black holes from traveling outwards to perform this "reionization." Therefore, stars and not growing black holes are likely to have cleared this fog at cosmic dawn.

Chandra is capable of detecting extremely faint objects at vast distances, but these black holes are so obscured that relatively few photons can escape and hence they could not be individually detected. Instead, the team used a technique that relied on Chandra's ability to accurately determine the direction from which the X-rays came to add up all the X-ray counts near the positions of distant galaxies and find a statistically significant signal.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

More information, including images and other multimedia, can be found at: http://chandra.si.edu

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA.

Journal Reference:

Ezequiel Treister, Kevin Schawinski, Marta Volonteri, Priyamvada Natarajan, Eric Gawiser. Black hole growth in the early Universe is self-regulated and largely hidden from view. Nature, 2011; 474 (7351): 356 DOI: 10.1038/nature10103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

NASA's Chandra finds massive black holes common in early universe

ScienceDaily (June 15, 2011) — Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies.

By pointing Chandra at a patch of sky for more than six weeks, astronomers obtained what is known as the Chandra Deep Field South (CDFS). When combined with very deep optical and infrared images from NASA's Hubble Space Telescope, the new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the universe was between about 800 million to 950 million years old.

"Until now, we had no idea what the black holes in these early galaxies were doing, or if they even existed," said Ezequiel Treister of the University of Hawaii, lead author of the study appearing in the June 16 issue of the journal Nature. "Now we know they are there, and they are growing like gangbusters."

The super-sized growth means that the black holes in the CDFS are less extreme versions of quasars -- very luminous, rare objects powered by material falling onto supermassive black holes. However, the sources in the CDFS are about a hundred times fainter and the black holes are about a thousand times less massive than the ones in quasars.

The observations found that between 30 and 100 percent of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the small observed field to the full sky, there are at least 30 million supermassive black holes in the early universe. This is a factor of 10,000 larger than the estimated number of quasars in the early universe.

"It appears we've found a whole new population of baby black holes," said co-author Kevin Schawinski of Yale University. "We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later."

A population of young black holes in the early universe had been predicted, but not yet observed. Detailed calculations show that the total amount of black hole growth observed by this team is about a hundred times higher than recent estimates.

Because these black holes are nearly all enshrouded in thick clouds of gas and dust, optical telescopes frequently cannot detect them. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

Physicists studying black holes want to know more how the first supermassive black holes were formed and how they grow. Although evidence for parallel growth of black holes and galaxies has been established at closer distances, the new Chandra results show that this connection starts earlier than previously thought, perhaps right from the origin of both.

"Most astronomers think in the present-day universe, black holes and galaxies are somehow symbiotic in how they grow," said Priya Natarajan, a co-author from Yale University. "We have shown that this codependent relationship has existed from very early times."

It has been suggested that early black holes would play an important role in clearing away the cosmic "fog" of neutral, or uncharged, hydrogen that pervaded the early universe when temperatures cooled down after the Big Bang. However, the Chandra study shows that blankets of dust and gas stop ultraviolet radiation generated by the black holes from traveling outwards to perform this "reionization." Therefore, stars and not growing black holes are likely to have cleared this fog at cosmic dawn.

Chandra is capable of detecting extremely faint objects at vast distances, but these black holes are so obscured that relatively few photons can escape and hence they could not be individually detected. Instead, the team used a technique that relied on Chandra's ability to accurately determine the direction from which the X-rays came to add up all the X-ray counts near the positions of distant galaxies and find a statistically significant signal.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

More information, including images and other multimedia, can be found at: http://chandra.si.edu

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA.

Journal Reference:

Ezequiel Treister, Kevin Schawinski, Marta Volonteri, Priyamvada Natarajan, Eric Gawiser. Black hole growth in the early Universe is self-regulated and largely hidden from view. Nature, 2011; 474 (7351): 356 DOI: 10.1038/nature10103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Meteorite holds clues to organic chemistry of early Earth

ScienceDaily (June 9, 2011) — Carbonaceous chondrites are a type of organic-rich meteorite that contain samples of the materials that took part in the creation of our planets nearly 4.6 billion years ago, including materials that were likely formed before our Solar System was created and may have been crucial to the formation of life on Earth. The complex suite of organic materials found in carbonaceous chondrites can vary substantially from meteorite to meteorite.

New research from Carnegie's Department of Terrestrial Magnetism and Geophysical Laboratory, published June 10 in Science, shows that most of these variations are the result of hydrothermal activity that took place within a few million years of the formation of the Solar System, when the meteorites were still part of larger parent bodies, likely asteroids.

Organic material in carbonaceous chondrites shares many characteristics with organic matter found in other primitive samples, including interplanetary dust particles, comet 81P/Wild-2, and Antarctic micrometeorites. It has been argued by some that this similarity indicates that organic material throughout the Solar System largely originated from a common source, possibly the interstellar medium.

A test of this common-source hypothesis stems from its requirement that the organic diversity within and among meteorites be due primarily to chemical and thermal processing that took place while the meteorites were parts of their parent bodies. In other words, there should be a relationship between the extent of hydrothermal alteration that a meteorite experienced and the chemistry of the organic material it contains.

If--as many have speculated--the organic material in meteorites had a role to play in the origin of life on Earth, the attraction of the common-source hypothesis is that the same organic material would have been delivered to all bodies in the Solar System. If the common source was the interstellar medium, then similar material would also be delivered to any forming planetary system.

The research team -- led by Christopher Herd of the University of Alberta, Canada, and including Carnegie's Conel Alexander, Larry Nittler, Frank Gyngard, George Cody, Marilyn Fogel, and Yoko Kebukawa -- studied four meteorite specimens from the shower of stones, produced by the breakup of a meteoroid as it entered the atmosphere, that fell on Tagish Lake in northern Canada in January 2000. The samples are considered very pristine, because they fell on a frozen lake, were collected without hand contact within a few days of landing and have remained frozen ever since.

The samples were processed and analyzed on the microscopic level using a variety of sophisticated techniques. Examination of their inorganic components indicated that the specimens had experienced large differences in the extent of hydrothermal alteration, prompting an in-depth examination of their organic material. The team demonstrated that the insoluble organic matter found in the samples has properties that span nearly the entire range found in all carbonaceous chondrites and that those properties correlate with other measures of the extent of parent body alteration. Their finding confirms that the diversity of this material is due to processing of a common precursor material in the asteroidal parent bodies.

The team found large concentrations of monocarboxylic acids, or MCAs, which are essential to biochemistry, in their Tagish Lake samples. They attributed the high level of these acids to the pristine nature of the samples, which have been preserved below zero degrees Celsius since they were recovered. There was variety in the types of MCAs, which they determined could also be due to alterations that took place on the parent bodies.

The samples also contained amino acids -- the essential-for-life organic building blocks used to create proteins. The types and abundances of amino acids contained in the samples are consistent with an extraterrestrial origin, and were clearly also influenced, albeit in a complex way, by the alteration histories of their host meteorites.

"Taken together these results indicate that the chemical and thermal processing common to the Tagish Lake meteorites likely occurred when the samples were part of a larger parent body that was created from the same raw materials that formed our Solar System," said Larry Nittler of Carnegie's DTM. "These samples can also provide important clues to the source of organic material, and life, on Earth."

Funding was provided by Natural Sciences and Engineering Research Council of Canada, Alberta Innovates, NASA (Astrobiology, including NASA Astrobiology Institute teams at the Carnegie Institution and the Goddard Center for Astrobiology; Origins of Solar Systems; Cosmochemistry and Postdoctoral Programs), the U.S. Office of Naval Research, Carnegie Institution for Science, Grant MacEwan University, and the Carnegie Institution of Canada. Some data was acquired at Advanced Light Source, which is supported by the Director of the Office of Science, Department of Energy, and by a W.M. Keck Foundation grant to the Carnegie Institution for Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Journal Reference:

Christopher D. K. Herd, Alexandra Blinova, Danielle N. Simkus, Yongsong Huang, Rafael Tarozo, Conel M. O’D. Alexander, Frank Gyngard, Larry R. Nittler, George D. Cody, Marilyn L. Fogel, Yoko Kebukawa, A. L. David Kilcoyne, Robert W. Hilts, Greg F. Slater, Daniel P. Glavin, Jason P. Dworkin, Michael P. Callahan, Jamie E. Elsila, Bradley T. De Gregorio, Rhonda M. Stroud. Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite. Science, 2011; 332 (6035): 1304-1307 DOI: 10.1126/science.1203290

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Meteorite holds clues to organic chemistry of early Earth

ScienceDaily (June 9, 2011) — Carbonaceous chondrites are a type of organic-rich meteorite that contain samples of the materials that took part in the creation of our planets nearly 4.6 billion years ago, including materials that were likely formed before our Solar System was created and may have been crucial to the formation of life on Earth. The complex suite of organic materials found in carbonaceous chondrites can vary substantially from meteorite to meteorite.

New research from Carnegie's Department of Terrestrial Magnetism and Geophysical Laboratory, published June 10 in Science, shows that most of these variations are the result of hydrothermal activity that took place within a few million years of the formation of the Solar System, when the meteorites were still part of larger parent bodies, likely asteroids.

Organic material in carbonaceous chondrites shares many characteristics with organic matter found in other primitive samples, including interplanetary dust particles, comet 81P/Wild-2, and Antarctic micrometeorites. It has been argued by some that this similarity indicates that organic material throughout the Solar System largely originated from a common source, possibly the interstellar medium.

A test of this common-source hypothesis stems from its requirement that the organic diversity within and among meteorites be due primarily to chemical and thermal processing that took place while the meteorites were parts of their parent bodies. In other words, there should be a relationship between the extent of hydrothermal alteration that a meteorite experienced and the chemistry of the organic material it contains.

If--as many have speculated--the organic material in meteorites had a role to play in the origin of life on Earth, the attraction of the common-source hypothesis is that the same organic material would have been delivered to all bodies in the Solar System. If the common source was the interstellar medium, then similar material would also be delivered to any forming planetary system.

The research team -- led by Christopher Herd of the University of Alberta, Canada, and including Carnegie's Conel Alexander, Larry Nittler, Frank Gyngard, George Cody, Marilyn Fogel, and Yoko Kebukawa -- studied four meteorite specimens from the shower of stones, produced by the breakup of a meteoroid as it entered the atmosphere, that fell on Tagish Lake in northern Canada in January 2000. The samples are considered very pristine, because they fell on a frozen lake, were collected without hand contact within a few days of landing and have remained frozen ever since.

The samples were processed and analyzed on the microscopic level using a variety of sophisticated techniques. Examination of their inorganic components indicated that the specimens had experienced large differences in the extent of hydrothermal alteration, prompting an in-depth examination of their organic material. The team demonstrated that the insoluble organic matter found in the samples has properties that span nearly the entire range found in all carbonaceous chondrites and that those properties correlate with other measures of the extent of parent body alteration. Their finding confirms that the diversity of this material is due to processing of a common precursor material in the asteroidal parent bodies.

The team found large concentrations of monocarboxylic acids, or MCAs, which are essential to biochemistry, in their Tagish Lake samples. They attributed the high level of these acids to the pristine nature of the samples, which have been preserved below zero degrees Celsius since they were recovered. There was variety in the types of MCAs, which they determined could also be due to alterations that took place on the parent bodies.

The samples also contained amino acids -- the essential-for-life organic building blocks used to create proteins. The types and abundances of amino acids contained in the samples are consistent with an extraterrestrial origin, and were clearly also influenced, albeit in a complex way, by the alteration histories of their host meteorites.

"Taken together these results indicate that the chemical and thermal processing common to the Tagish Lake meteorites likely occurred when the samples were part of a larger parent body that was created from the same raw materials that formed our Solar System," said Larry Nittler of Carnegie's DTM. "These samples can also provide important clues to the source of organic material, and life, on Earth."

Funding was provided by Natural Sciences and Engineering Research Council of Canada, Alberta Innovates, NASA (Astrobiology, including NASA Astrobiology Institute teams at the Carnegie Institution and the Goddard Center for Astrobiology; Origins of Solar Systems; Cosmochemistry and Postdoctoral Programs), the U.S. Office of Naval Research, Carnegie Institution for Science, Grant MacEwan University, and the Carnegie Institution of Canada. Some data was acquired at Advanced Light Source, which is supported by the Director of the Office of Science, Department of Energy, and by a W.M. Keck Foundation grant to the Carnegie Institution for Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Journal Reference:

Christopher D. K. Herd, Alexandra Blinova, Danielle N. Simkus, Yongsong Huang, Rafael Tarozo, Conel M. O’D. Alexander, Frank Gyngard, Larry R. Nittler, George D. Cody, Marilyn L. Fogel, Yoko Kebukawa, A. L. David Kilcoyne, Robert W. Hilts, Greg F. Slater, Daniel P. Glavin, Jason P. Dworkin, Michael P. Callahan, Jamie E. Elsila, Bradley T. De Gregorio, Rhonda M. Stroud. Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite. Science, 2011; 332 (6035): 1304-1307 DOI: 10.1126/science.1203290

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Antibody-based biosensor can guide environmental clean-ups, provide early warning system for spills

ScienceDaily (May 9, 2011) — Tests of a new antibody-based "biosensor" developed by researchers at the Virginia Institute of Marine Science show that it can detect marine pollutants like oil much faster and more cheaply than current technologies. The device is small and sturdy enough to be used from a boat.

Testing of the biosensor in the Elizabeth River and Yorktown Creek, which both drain into lower Chesapeake Bay, shows that the instrument can process samples in less than 10 minutes, detect pollutants at levels as low as just a few parts per billion, and do so at a cost of just pennies per sample. Current technology requires hours of lab work, with a per-sample cost of up to $1,000.

"Our biosensor combines the power of the immune system with the sensitivity of cutting-edge electronics," says Dr. Mike Unger of VIMS. "It holds great promise for real-time detection and monitoring of oil spills and other releases of contaminants into the marine environment."

The biosensor was developed and tested by Unger, fellow VIMS professor Steve Kaattari, and their doctoral student Candace Spier, with assistance from marine scientist George Vadas. The team's report of field tests with the sensor appears in this month's issue of Environmental Toxicology and Chemistry.

The instrument was developed in conjunction with Sapidyne Instruments, Inc., with funding from the state of Virginia, the Office of Naval Research, and the Cooperative Institute for Coastal and Estuarine Environmental Technology, a partnership between NOAA and the University of New Hampshire.

The tests in the Elizabeth River took place during clean up of a site contaminated by polycyclic aromatic hydrocarbons (PAHs), byproducts of decades of industrial use of creosote to treat marine pilings. The U.S. Environmental Protection Agency considers PAHs highly toxic and lists 17 as suspected carcinogens.

The biosensor allowed the researchers to quantify PAH concentrations while the Elizabeth River remediation was taking place, gaining on-site knowledge about water quality surrounding the remediation site. Spier says the test was "the first use of an antibody-based biosensor to guide sampling efforts through near real-time evaluation of environmental contamination."

In the Yorktown Creek study, the researchers used the biosensor to track the runoff of PAHs from roadways and soils during a rainstorm.

Biosensor development

Kaattari says "Our basic idea was to fuse two different kinds of technologies -- monoclonal antibodies and electronic sensors -- in order to detect contaminants."

Antibodies are proteins produced by the immune system of humans and other mammals. They are particularly well suited for detecting contaminants because they have, as Kaattari puts it, an "almost an infinite power to recognize the 3-dimensional shape of any molecule."

Mammals produce antibodies that recognize and bind with large organic molecules such as proteins or with viruses. The VIMS team took this process one step further, linking proteins to PAHs and other contaminants, then exposing mice to these paired compounds in a manner very similar to a regular vaccination.

"Just like you get vaccinated against the flu, we in essence are vaccinating our mice against contaminants," says Kaattari. "The mouse's lymphatic system then produces antibodies to PAHs, TNT, tributyl tin [TBT, the active ingredient in anti-fouling paints for boats], or other compounds."

Once a mouse has produced an antibody to a particular contaminant, the VIMS team applies standard clinical techniques to produce "monoclonal antibodies" in sufficiently large quantities for use in a biosensor.

"This technology allows you to immortalize a lymphocyte that produces only a very specific antibody," says Kaattari. "You grow the lymphocytes in culture and can produce large quantities of antibodies within a couple of weeks. You can preserve the antibody-producing lymphocyte forever, which means you don't have to go to a new animal every time you need to produce new antibodies."

From antibody to electrical signal

The team's next step was to develop a sensor that can recognize when an antibody binds with a contaminant and translate that recognition into an electrical signal. The Sapidyne® sensor used by the VIMS team works via what Kaattari calls a "fluorescence-inhibitory, spectroscopic kind of assay."

In the sensor used on the Elizabeth River and Yorktown Creek, antibodies designed to recognize a specific class of PAHs were joined with a dye that glows when exposed to fluorescent light. The intensity of that light is in turn recorded as a voltage. The sensor also houses tiny plastic beads that are coated with what Spier calls a "PAH surrogate" -- a PAH derivative that retains the shape that the antibody recognizes as a PAH molecule.

When water samples with low PAH levels are added to the sensor chamber (which is already flooded with a solution of anti-PAH antibodies), the antibodies have little to bind with and are thus free to attach to the surrogate-coated beads, providing a strong fluorescent glow and electric signal. In water samples with high PAH concentrations, on the other hand, a large fraction of the antibodies bind with the environmental contaminants. That leaves fewer to attach to the surrogate-coated beads, which consequently provides a fainter glow and a weaker electric signal.

During the Elizabeth River study, the biosensor measured PAH concentrations that ranged from 0.3 to 3.2 parts per billion, with higher PAH levels closer to the dredge site. In Yorktown Creek, the biosensor showed that PAH levels in runoff peaked 1 to 2 hours after the rain started, with peak concentration of 4.4 parts per billion.

Comparison of the biosensor's field readings with later readings from a mass spectrometer at VIMS showed that the biosensor is just as accurate as the more expensive, slower, and laboratory-bound machine.

A valuable field tool

Spier says "Using the biosensor allowed us to quickly survey an area of almost 900 acres around the Elizabeth River dredge, and to provide information about the size and intensity of the contaminant plume to engineers monitoring the dredging from shore. If our results had shown elevated concentrations, they could have halted dredging and put remedial actions in place."

Unger adds "measuring data in real-time also allowed us to guide the collection of large-volume water samples right from the boat. We used these samples for later analysis of specific PAH compounds in the lab. This saved time, effort, and money by keeping us from having to analyze samples that might contain PAHs at levels below our detection limit."

"Biosensors have their constraints and optimal operating conditions," says Kaattari, "but their promise far outweighs any limitations. The primary advantages of our biosensor are its sensitivity, speed, and portability. These instruments are sure to have a myriad of uses in future environmental monitoring and management."

One promising use of the biosensor is for early detection and tracking of oil spills. "If biosensors were placed near an oil facility and there was a spill, we would know immediately," says Kaattari. "And because we could see concentrations increasing or decreasing in a certain pattern, we could also monitor the dispersal over real time."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Virginia Institute of Marine Science. The original article was written by David Malmquist.

Journal Reference:

Candace R. Spier, George G. Vadas, Stephen L. Kaattari, Michael A. Unger. Near real-time, on-site, quantitative analysis of PAHs in the aqueous environment using an antibody-based biosensor. Environmental Toxicology and Chemistry, 2011; DOI: 10.1002/etc.546

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Antibody-based biosensor can guide environmental clean-ups, provide early warning system for spills

ScienceDaily (May 9, 2011) — Tests of a new antibody-based "biosensor" developed by researchers at the Virginia Institute of Marine Science show that it can detect marine pollutants like oil much faster and more cheaply than current technologies. The device is small and sturdy enough to be used from a boat.

Testing of the biosensor in the Elizabeth River and Yorktown Creek, which both drain into lower Chesapeake Bay, shows that the instrument can process samples in less than 10 minutes, detect pollutants at levels as low as just a few parts per billion, and do so at a cost of just pennies per sample. Current technology requires hours of lab work, with a per-sample cost of up to $1,000.

"Our biosensor combines the power of the immune system with the sensitivity of cutting-edge electronics," says Dr. Mike Unger of VIMS. "It holds great promise for real-time detection and monitoring of oil spills and other releases of contaminants into the marine environment."

The biosensor was developed and tested by Unger, fellow VIMS professor Steve Kaattari, and their doctoral student Candace Spier, with assistance from marine scientist George Vadas. The team's report of field tests with the sensor appears in this month's issue of Environmental Toxicology and Chemistry.

The instrument was developed in conjunction with Sapidyne Instruments, Inc., with funding from the state of Virginia, the Office of Naval Research, and the Cooperative Institute for Coastal and Estuarine Environmental Technology, a partnership between NOAA and the University of New Hampshire.

The tests in the Elizabeth River took place during clean up of a site contaminated by polycyclic aromatic hydrocarbons (PAHs), byproducts of decades of industrial use of creosote to treat marine pilings. The U.S. Environmental Protection Agency considers PAHs highly toxic and lists 17 as suspected carcinogens.

The biosensor allowed the researchers to quantify PAH concentrations while the Elizabeth River remediation was taking place, gaining on-site knowledge about water quality surrounding the remediation site. Spier says the test was "the first use of an antibody-based biosensor to guide sampling efforts through near real-time evaluation of environmental contamination."

In the Yorktown Creek study, the researchers used the biosensor to track the runoff of PAHs from roadways and soils during a rainstorm.

Biosensor development

Kaattari says "Our basic idea was to fuse two different kinds of technologies -- monoclonal antibodies and electronic sensors -- in order to detect contaminants."

Antibodies are proteins produced by the immune system of humans and other mammals. They are particularly well suited for detecting contaminants because they have, as Kaattari puts it, an "almost an infinite power to recognize the 3-dimensional shape of any molecule."

Mammals produce antibodies that recognize and bind with large organic molecules such as proteins or with viruses. The VIMS team took this process one step further, linking proteins to PAHs and other contaminants, then exposing mice to these paired compounds in a manner very similar to a regular vaccination.

"Just like you get vaccinated against the flu, we in essence are vaccinating our mice against contaminants," says Kaattari. "The mouse's lymphatic system then produces antibodies to PAHs, TNT, tributyl tin [TBT, the active ingredient in anti-fouling paints for boats], or other compounds."

Once a mouse has produced an antibody to a particular contaminant, the VIMS team applies standard clinical techniques to produce "monoclonal antibodies" in sufficiently large quantities for use in a biosensor.

"This technology allows you to immortalize a lymphocyte that produces only a very specific antibody," says Kaattari. "You grow the lymphocytes in culture and can produce large quantities of antibodies within a couple of weeks. You can preserve the antibody-producing lymphocyte forever, which means you don't have to go to a new animal every time you need to produce new antibodies."

From antibody to electrical signal

The team's next step was to develop a sensor that can recognize when an antibody binds with a contaminant and translate that recognition into an electrical signal. The Sapidyne® sensor used by the VIMS team works via what Kaattari calls a "fluorescence-inhibitory, spectroscopic kind of assay."

In the sensor used on the Elizabeth River and Yorktown Creek, antibodies designed to recognize a specific class of PAHs were joined with a dye that glows when exposed to fluorescent light. The intensity of that light is in turn recorded as a voltage. The sensor also houses tiny plastic beads that are coated with what Spier calls a "PAH surrogate" -- a PAH derivative that retains the shape that the antibody recognizes as a PAH molecule.

When water samples with low PAH levels are added to the sensor chamber (which is already flooded with a solution of anti-PAH antibodies), the antibodies have little to bind with and are thus free to attach to the surrogate-coated beads, providing a strong fluorescent glow and electric signal. In water samples with high PAH concentrations, on the other hand, a large fraction of the antibodies bind with the environmental contaminants. That leaves fewer to attach to the surrogate-coated beads, which consequently provides a fainter glow and a weaker electric signal.

During the Elizabeth River study, the biosensor measured PAH concentrations that ranged from 0.3 to 3.2 parts per billion, with higher PAH levels closer to the dredge site. In Yorktown Creek, the biosensor showed that PAH levels in runoff peaked 1 to 2 hours after the rain started, with peak concentration of 4.4 parts per billion.

Comparison of the biosensor's field readings with later readings from a mass spectrometer at VIMS showed that the biosensor is just as accurate as the more expensive, slower, and laboratory-bound machine.

A valuable field tool

Spier says "Using the biosensor allowed us to quickly survey an area of almost 900 acres around the Elizabeth River dredge, and to provide information about the size and intensity of the contaminant plume to engineers monitoring the dredging from shore. If our results had shown elevated concentrations, they could have halted dredging and put remedial actions in place."

Unger adds "measuring data in real-time also allowed us to guide the collection of large-volume water samples right from the boat. We used these samples for later analysis of specific PAH compounds in the lab. This saved time, effort, and money by keeping us from having to analyze samples that might contain PAHs at levels below our detection limit."

"Biosensors have their constraints and optimal operating conditions," says Kaattari, "but their promise far outweighs any limitations. The primary advantages of our biosensor are its sensitivity, speed, and portability. These instruments are sure to have a myriad of uses in future environmental monitoring and management."

One promising use of the biosensor is for early detection and tracking of oil spills. "If biosensors were placed near an oil facility and there was a spill, we would know immediately," says Kaattari. "And because we could see concentrations increasing or decreasing in a certain pattern, we could also monitor the dispersal over real time."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Virginia Institute of Marine Science. The original article was written by David Malmquist.

Journal Reference:

Candace R. Spier, George G. Vadas, Stephen L. Kaattari, Michael A. Unger. Near real-time, on-site, quantitative analysis of PAHs in the aqueous environment using an antibody-based biosensor. Environmental Toxicology and Chemistry, 2011; DOI: 10.1002/etc.546

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Early history of genetics revised: New light shed on 'rediscovery' of Mendel's laws of heredity

ScienceDaily (May 3, 2011) — The early history of genetics has to be re-written in the light of new findings. Scientists from the University Jena (Germany) in co-operation with colleagues from Prague found out that the traditional history of the 'rediscovery' of Gregor Johann Mendel's laws of heredity in 1900 has to be adjusted and some facets have to be added.

It all began in the year of 1865: Mendel, today known as the 'father of genetics', published his scientific findings about the cross breeding experiments of peas, that went largely unnoticed during his lifetime. His research notes and manuscripts disappeared after Mendel's death in 1884. Only about 1900 three scientists 'rediscovered' the later so called Mendel's laws: the Dutch biologist Hugo de Vries, the German plant geneticist Carl Correns, and the Austrian plant breeder Erich von Tschermak-Seysenegg.

"For 110 years many believed it to be like that," says Prof. Dr. Uwe Hoßfeld, leader of the Research Group Didactics of Biology of the University Jena. "But in reality there were four direct protagonists, 'rediscoverers' of Mendel's laws" as the historians of science and biologists found out recently. Moreover it was assumed that the research went on in parallel and independently. "The so far unknown and now edited correspondence of the brothers Armin und Erich von Tschermak-Seysenegg from 1898-1901 leads to a correction of the former assumption," according to Dr. Michal Simunek. Amongst other things the researchers could prove that some of the scientists should indeed exchange plant seeds and corresponded about the research results in their letters.

Recently two volumes dealing with selected problems of the early Mendel research from the scientific series 'Studies in the History of Sciences and Humanities' have been published. Volume No. 27 for the first time releases the so far unknown personal correspondence from the period between 1898-1951 of the brothers Armin and Erich von Tschermak-Seysenegg, the former being physiologist and the latter a plant breeder. The vast majority of them has been identified by Dr. Simunek in the family possession of Armin's grandson, Dr. Armin Tschermak von Seysenegg Jr. From 1900 Armin Tschermak von Seysenegg presented several writings which show that apart from de Vries and Correns his younger brother Erich took part in the research about Mendel's laws. However he excluded himself from the ranks of the so-called rediscoverers in spite of his active participation in the events of 1900 and 1901.

What were the reasons? Why did he step back and leave all the glory to his younger brother Erich? "The two of them were tied by such an unusual brotherly love that is otherwise rare amongst scientists," Hoßfeld reports on one possible reason. Erich took the credit as the 'rediscoverer' for a long time. He died in 1962. Armin, who died ten years earlier, however remained unknown person about these particular achievements to the public and thus allowed his brother's to overshadow him. At the same time the eye physiologist and later professor in Prague seemed to contribute especially as far as the statistical analysis concerned. Armin was widely interested in the subject of Mendel's laws (especially in the numeric ratio). Therefore his younger brother extensively consulted him on these problems. It can be assumed that the papers Erich Tschermak von Seysenegg presented in 1900 and 1901 respectively about the 'rediscovery' were actually the results of an intense co-operation with his older brother Armin. It is difficult though to reconstruct the whole amount of this fraternal teamwork as there are only a few of the older brother's letters still surviving. "After these new findings the traditional view of the early history of genetics has to be reviewed," both scientists are sure.

The second contribution to the history of the Gregor J. Mendel related research (Volume No. 28) contains the correspondence of Mendel's first biographers, among them Willam Bateson, Hugo Iltis and Erich Tschermak von Seysenegg, with Mendel's two nephews, Dr. Alois and Ferdinand Schindler, from the period between 1902-35. After 1900 the nephews became the most important sources for the biographical portrayal of Gregor J. Mendel. Their writings are mostly concerned with the family history and the last part of Mendel's life. This correspondence is published in such comprehensive volume for the first time.

In the German Research Council project about the early history of genetics in Bohemia and Moravia, Jena scientists co-operated with researchers from the Academy of Sciences in Prague as well as the Moravian Museum in Brno.

References:

Michal Simunek, Uwe Hoßfeld, Florian Thümmler, Olaf Breidbach (Eds.): The Mendelian Dioskuri -- Correspondence of Armin with Erich von Tschermak-Seysenegg, 1898-1951; „Studies in the History of Sciences and Humanities," Vol. No. 27; Prag 2011; ISBN 978-80-87378-67-0

Michal Simunek, Uwe Hoßfeld, Florian Thümmler, Jirí Sekerák (Eds.): The Letters on G. J. Mendel -- Correspondence of William Bateson, Hugo Iltis, and Erich von Tschermak-Seysenegg with Alois and Ferdinand Schindler, 1902-1935; „Studies in the History of Sciences and Humanities," Vol. No. 28; Prag 2011; ISBN 978-80-87378-73-1

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Friedrich-Schiller-Universitaet Jena.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Novel noninvasive tests for early cancer detection

ScienceDaily (May 3, 2011) — Researchers at last month's AACR conference in Orlando demonstrated that they are intensifying their efforts to identify and validate various types of biomarkers that are detectable in readily accessible bodily fluids such as blood and urine, reports Genetic Engineering & Biotechnology News (GEN). The goal is to detect biosignatures that are more specific and sensitive than existing diagnostic modalities, according to the May 1 issue of GEN .

"The molecular diagnostic approach is geared toward finding tumors earlier in the course of disease," says John Sterling, Editor in Chief of GEN. "This could reduce the need for more invasive and costly biopsies and imaging studies and lead to earlier therapeutic intervention."

At the AACR meeting, Harvey Pass, M.D., New York University Langone Medical Center and Cancer Center, discussed his group's experience working in collaboration with SomaLogic to develop an aptamer-based diagnostic to detect malignant mesothelioma in asbestos-exposed individuals. Dr. Pass presented data derived from the application of biomarker subsets to a blinded test set, demonstrating 100% specificity and 80% sensitivity for their ability to distinguish asbestos-exposed controls from mesothelioma cases.

Another presentation pointed out that measurement of CA125 in the blood is the test currently used to monitor ovarian cancer treatment, follow patients for recurrence, and in some cases screen high-risk individuals to detect early-stage disease. In her conference talk, Christine Coticchia, Ph.D., Children's Hospital Boston and Harvard Medical School, emphasized that CA125 is relatively nonspecific for ovarian cancer and uninformative in a substantial percentage of patients. Dr. Coticchia and colleagues are studying a combination of two matrix metalloproteases, MMP-2 and MMP-9, in urine for their utility as biomarkers to predict the presence of ovarian cancer in women with normal CA125 levels.

Other research projects covered in the GEN article include work at Celera, the Fred Hutchinson Cancer Research Center, University of Michigan Health System, Gen-Probe, University of California at San Diego Medical Center, Université Laval, Dianon Systems, Aarhus University Hospital, Hvidovre Hospital, University of Copenhagen, and Exiqon.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Mary Ann Liebert, Inc./Genetic Engineering News, via EurekAlert!, a service of AAAS.

Journal Reference:

Vicki Glaser. Cancer Detection Improved with Noninvasive Testing. Genetic Engineering & Biotechnology News, May 1, 2011 (Vol. 31, No. 9) [link]

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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Early meat-eating dinosaur unearthed

At roughly 4 feet high and 10 to 15 pounds in weight, the newfound primitive dinosaur Eodromaeus would have been an agile but not fearsome hunter.Illustration by Todd Marshall

The dinosaur family tree just added a new relative: a small, nipping, meat-eating creature dating back to dinosaurs’ earliest days.

Unearthed in 230-million-year-old rocks in Argentina, in life this bipedal animal would have been as tall as a 7-year-old but as light as a house cat. Paleontologists announced the new dinosaur, dubbed Eodromaeus, or “dawn runner,” in the Jan. 14 Science.

Eodromaeus joins its kin Eoraptor, a similar-sized dinosaur known to have lived in the same time and place. In fact, when researchers first unearthed Eodromaeus they thought the bones belonged to Eoraptor. Yet the two dinosaurs’ superficial resemblance belies a crucial difference: one ate plants while the other ate meat.

“From 20 feet away you’d do a double take — will the animal run from you or take your leg off?” says team member Paul Sereno, a paleontologist at the University of Chicago. Yet each creature eventually led to a separate branch of dinosaur evolution. “There’s no way to look at them and realize that the ultimate descendants of one results in a tyrannosaur, and the other something like [the plant-eating] Diplodocus,” Sereno says.

The Science paper describes not only the newfound remains of Eodromaeus, but also a wealth of other Argentinean fossils that illuminate how the earliest dinosaurs evolved and what their environment was like. “The new dinosaur is special for sure, but we also have the first step of the radiation of the dinosaur story,” says Ricardo Martinez, the paper’s lead author and a paleontologist at the National University of San Juan in Argentina.

Fossil evidence shows that the first dinosaurs appeared around 230 million years ago, as ecosystems were rejiggering themselves after a massive extinction that ended the Permian period, 250 million years ago. Many researchers have thought that as dinosaurs rose to prominence they muscled out other animal groups.

But Martinez’s team analyzed rates of biodiversity in the Argentinean rocks and found the opposite: Other groups of plant-eating creatures underwent a small-scale extinction before dinosaurs began their rise. “Dinosaurs used those empty ecological niches,” Martinez says. From there dinosaurs went on to become Earth’s dominant land animals until going extinct 65 million years ago — save for the avian branch, which thrives today as birds.

Distinguishing early dinos from each other isn’t easy, as their fossils lie so close to the initial evolutionary radiation. “When you find animals that evolved just after the split of major branches, they’re all going to look really similar,” says Randall Irmis, curator of paleontology at the Utah Museum of Natural History and an assistant professor in geology at the University of Utah in Salt Lake City.

Sereno discovered Eoraptor in 1991, and he later described it as a theropod, a group of dinosaurs that mainly ate meat. After doing more detailed studies, the team decided to reclassify Eoraptor in the new paper as an early sauropod, the other main group of dinosaurs, which mainly ate plants.

Unlike Eoraptor’s identification, Eodromaeus’ classification as a theropod is right from the start, researchers believe. It has sharp teeth for cutting meat, says Martinez, as well as long finger bones for grasping, and interlocking mechanisms in its bones that stiffen the tail to help while hunting.

Eodromaeus joins not only Eoraptor but also a host of other early dinosaurs that roamed what is now Argentina, such as the two-legged sauropod Panphagia, reported by Martinez in 2009. All come from the picturesquely named Valley of the Moon in northeastern Argentina and are buried in a fossil mother lode known as the Ischigualasto.

“What we have is this unbelievable graveyard of the earlier dinosaurs,” says Sereno. “We don’t have a lot of places like this.”

Unfortunately, this dinosaur trove ends with the Ischigualasto rocks. The older rocks beneath it, says Martinez, have preserved only fossils of plants.

Found in: Earth, Life and Paleontology

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Oceans may have poisoned early animals

Soon after complex animals made their first great strides onto the stage of life, the oceans brewed up a toxic chemical mix that put the brakes on evolutionary innovation, suggests a paper in the Jan. 6 Nature.

The culprits? Too little oxygen and too much sulfur dissolved in coastal waters, reports a team led by geochemist Benjamin Gill of Harvard University. Ancient creatures such as trilobites and brachiopods could not cope with the changes, and many of them went extinct.

The “remarkable” new data are the first to link a changing ocean environment to some of the extinctions that took place between about 490 million and 520 million years ago, says Graham Shields-Zhou, a geologist at University College London who was not on the research team.

Perhaps not surprisingly, marine creatures are exquisitely sensitive to their surroundings, suffocating when oxygen levels drop. Other big extinctions, like one that occurred around 400 million years ago and another around 250 million years ago, have also been blamed on low levels of oceanic oxygen. But the more ancient extinctions studied by Gill, which took place in the later part of the Cambrian period, are of particular interest because they came soon after the “Cambrian explosion” in which animals blossomed in biodiversity.

Gill’s team decided to look at a specific subset of Cambrian extinctions that began 499 million years ago and lasted for 2 million to 4 million years. Other researchers had proposed that low oxygen levels — a condition known as anoxia — could be involved. But no one had marshaled enough evidence to prove that. Gill and his colleagues are the first to look at sulfur along with other elements, to piece together a complete picture of what was happening in the oceans. High levels of sulfur can kill marine creatures.

The researchers traveled the globe to collect rock samples of the proper age from Nevada, Utah, Missouri, Australia and Sweden. By analyzing sulfur and carbon isotopes — different forms of an element that vary in atomic mass — the scientists could track changes such as sediment being buried on the ocean bottom, a process that alters chemistry in the waters above.

The amount of carbon in the rocks, as compared to the amount of sulfur, could only have come about if the water were low in oxygen and high in the sulfide form of sulfur, the team reports. Today, a similar environment can be found in the oxygen-starved Black Sea, says Gill.

Most of the toxic waters would have shoaled up along the coasts, where the majority of animals lived. Overall, the new data suggest how pulses of rising and falling oxygen and sulfur could have repeatedly devastated marine ecosystems, says Shields.

Although the researchers think the Cambrian oceans were toxic,
they don’t know why. “What we’re looking at is the aftermath of the crime scene,” says Gill. “We don’t have the cause for why the oceans suddenly went anoxic.”

His team plans to broaden the search to see if some of the other late-Cambrian extinctions could also be linked to toxic oceans.

Poisonous waters could have even been the norm through much of the planet's history, adds Isabel Montañez, a geologist at the University of California, Davis. The new work, she says, "begs the question as to whether ocean anoxic events were a recurrent theme in the oceans that hosted Earth's early metazoan life."

Found in: Earth and Paleobiology

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