Smurf-Herder
01-15-2009, 05:26 PM
Bacteria May Be Source of Methane on Mars
By KENNETH CHANG
Published: January 15, 2009
In early 2003, a plume of methane gas rose from the surface of Mars.
The big unanswered question: what belched?
Subsurface Martian cows appear unlikely, but scientists are seriously considering the possibility that bacteria are generating the methane.
A team of researchers reported Thursday that methane emissions on Mars appear to come in large, brief bursts and that in 2003, the bursts originated from three specific regions in the northern hemisphere, where it was midsummer.
The gas came out at a rate of 0.6 kilograms a second, the scientists said, and the plume contained 19,000 metric tons of methane. If the release was caused by the warm season, the scientists determined that 42,000 metric tons of methane would have been released over the full summer.
“This is the first definitive detection of methane on Mars,” Michael J. Mumma, a senior scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and leader of the research team, said during a NASA news conference, “and the first definitive maps and identification of active regions of release.”
The findings appear in a paper published online on Thursday by the journal Science. Dr. Mumma has previously reported some of his findings at scientific meetings, but the Science paper is the first time they have appeared in a peer-reviewed journal. Dr. Mumma said additional scientific papers describing other time periods of the observations, which span from 2001 to 2008, were being prepared.
Methane, the simplest of hydrocarbon molecules, with one carbon atom and four hydrogen atoms, is fragile in air. It falls apart when hit by ultraviolet radiation in sunlight. That means any methane in the Martian air must have been released recently.
When the 2003 methane emissions were reported in 2004 by three teams of scientists, the findings generated surprise and skepticism, because only a few explanations appear plausible.
One is geothermal chemical reactions involving water and heat in volcanoes or underground hot springs. But evidence for recent volcanism on Mars is scarce. Also, volcanoes would be expected to spew other gases like sulfur dioxide, but those are not plentiful in the Martian air.
“That part of the evidence does not support a volcanic origin,” Dr. Mumma said.
A second possibility is biological. On Earth, a class of bacteria known as methanogens breathes out methane as a waste product.
NASA’s current Mars strategy is to look for signs of water and perhaps life in Mars’ distant past. “Perhaps we need to also think in terms of present-day life holding on somewhere in the subsurface,” said Lisa Pratt, a professor of geological sciences at Indiana University who participated in the news conference but was not involved with the research.
Even if the source turns out to be geological in origin or to have come from long-extinct bacteria, the sites would still be prime locations to look for other microbes that thrive on methane as food. “It gives us a bulls-eye to go after,” Dr. Pratt said.
Because of the difficulty in measuring methane, many scientists wondered if the earlier reports really showed methane or if all three teams had been misled by their data.
Dr. Mumma’s group used telescopes in Hawaii to examine the light reflected off Mars. Different molecules absorb different wavelengths of light, and the scientists reported seeing black lines in the spectrum corresponding to methane as well as water vapor. As Mars rotated, bringing different areas into view of the telescope, the scientists could measure the methane concentrations.
The concentrations in 2003 were densest over three regions known as Terra Sabae, Nili Fossae and Syrtis Major, as high as 45 parts per billion, meaning that of each billion molecules of Martian air, 45 were methane. The scientists said that mineralogy of the surface suggested these areas had flowing water in the far Martian past.
Nili Fossae had been under consideration for the landing site for the Mars Science Laboratory, NASA’s next surface rover, but was not among the four finalist sites announced in November. In December, scientists reported that the Mars Reconnaissance Orbiter had spotted exposed outcrops of carbonate rocks in Nili Fossae, perhaps the vestige of ancient lakes and seas.
At the news conference, Michael Meyer, the lead scientist for the Mars program at NASA headquarters, said that a recent decision to delay the launching of the rover to 2011 from 2009 could allow reconsideration of Nili Fossae. An instrument aboard the science laboratory would be able to detect methane at levels of 100 parts per trillion.
The current NASA rovers on Mars do not have any methane-sniffing instruments and neither do NASA’s current or planned orbiters. Scientists working with European Space Agency’s Mars Express spacecraft composed another of the teams who reported the detection of methane in 2003, but the evidence was just barely discernible.
The 42,000 metric tons of methane released in 2003 would have quickly dispersed, to a global average of 6 parts per billion.
Dr. Mumma’s team also detected methane in 2006, but at a global concentration of only 3 parts per billion, raising a second mystery about what happened to the other half of the methane. Ultraviolet light would take more than a century to destroy that much methane. One possibility is that hydrogen peroxide, known to exist in the atmosphere, reacts with the methane and destroys it.
http://www.nytimes.com/2009/01/16/science/space/16mars.html?ref=science
By KENNETH CHANG
Published: January 15, 2009
In early 2003, a plume of methane gas rose from the surface of Mars.
The big unanswered question: what belched?
Subsurface Martian cows appear unlikely, but scientists are seriously considering the possibility that bacteria are generating the methane.
A team of researchers reported Thursday that methane emissions on Mars appear to come in large, brief bursts and that in 2003, the bursts originated from three specific regions in the northern hemisphere, where it was midsummer.
The gas came out at a rate of 0.6 kilograms a second, the scientists said, and the plume contained 19,000 metric tons of methane. If the release was caused by the warm season, the scientists determined that 42,000 metric tons of methane would have been released over the full summer.
“This is the first definitive detection of methane on Mars,” Michael J. Mumma, a senior scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and leader of the research team, said during a NASA news conference, “and the first definitive maps and identification of active regions of release.”
The findings appear in a paper published online on Thursday by the journal Science. Dr. Mumma has previously reported some of his findings at scientific meetings, but the Science paper is the first time they have appeared in a peer-reviewed journal. Dr. Mumma said additional scientific papers describing other time periods of the observations, which span from 2001 to 2008, were being prepared.
Methane, the simplest of hydrocarbon molecules, with one carbon atom and four hydrogen atoms, is fragile in air. It falls apart when hit by ultraviolet radiation in sunlight. That means any methane in the Martian air must have been released recently.
When the 2003 methane emissions were reported in 2004 by three teams of scientists, the findings generated surprise and skepticism, because only a few explanations appear plausible.
One is geothermal chemical reactions involving water and heat in volcanoes or underground hot springs. But evidence for recent volcanism on Mars is scarce. Also, volcanoes would be expected to spew other gases like sulfur dioxide, but those are not plentiful in the Martian air.
“That part of the evidence does not support a volcanic origin,” Dr. Mumma said.
A second possibility is biological. On Earth, a class of bacteria known as methanogens breathes out methane as a waste product.
NASA’s current Mars strategy is to look for signs of water and perhaps life in Mars’ distant past. “Perhaps we need to also think in terms of present-day life holding on somewhere in the subsurface,” said Lisa Pratt, a professor of geological sciences at Indiana University who participated in the news conference but was not involved with the research.
Even if the source turns out to be geological in origin or to have come from long-extinct bacteria, the sites would still be prime locations to look for other microbes that thrive on methane as food. “It gives us a bulls-eye to go after,” Dr. Pratt said.
Because of the difficulty in measuring methane, many scientists wondered if the earlier reports really showed methane or if all three teams had been misled by their data.
Dr. Mumma’s group used telescopes in Hawaii to examine the light reflected off Mars. Different molecules absorb different wavelengths of light, and the scientists reported seeing black lines in the spectrum corresponding to methane as well as water vapor. As Mars rotated, bringing different areas into view of the telescope, the scientists could measure the methane concentrations.
The concentrations in 2003 were densest over three regions known as Terra Sabae, Nili Fossae and Syrtis Major, as high as 45 parts per billion, meaning that of each billion molecules of Martian air, 45 were methane. The scientists said that mineralogy of the surface suggested these areas had flowing water in the far Martian past.
Nili Fossae had been under consideration for the landing site for the Mars Science Laboratory, NASA’s next surface rover, but was not among the four finalist sites announced in November. In December, scientists reported that the Mars Reconnaissance Orbiter had spotted exposed outcrops of carbonate rocks in Nili Fossae, perhaps the vestige of ancient lakes and seas.
At the news conference, Michael Meyer, the lead scientist for the Mars program at NASA headquarters, said that a recent decision to delay the launching of the rover to 2011 from 2009 could allow reconsideration of Nili Fossae. An instrument aboard the science laboratory would be able to detect methane at levels of 100 parts per trillion.
The current NASA rovers on Mars do not have any methane-sniffing instruments and neither do NASA’s current or planned orbiters. Scientists working with European Space Agency’s Mars Express spacecraft composed another of the teams who reported the detection of methane in 2003, but the evidence was just barely discernible.
The 42,000 metric tons of methane released in 2003 would have quickly dispersed, to a global average of 6 parts per billion.
Dr. Mumma’s team also detected methane in 2006, but at a global concentration of only 3 parts per billion, raising a second mystery about what happened to the other half of the methane. Ultraviolet light would take more than a century to destroy that much methane. One possibility is that hydrogen peroxide, known to exist in the atmosphere, reacts with the methane and destroys it.
http://www.nytimes.com/2009/01/16/science/space/16mars.html?ref=science