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Post by Chicago Astronomer Joe on Jul 21, 2005 4:02:50 GMT -6
Methane On Mars
Moffett Field CA (SPX) Jul 21, 2005 Mars is the planet that refuses to say "die." In 1996, after centuries of speculation about canals, icecaps and vegetation, NASA's David McKay reported seeing traces of ancient bacteria in a meteorite from Mars. Scientists have debated this finding ever since, and many now believe that the intriguing traces are probably not of biological origin.
Within the last few years, however, two simple chemicals intimately associated with life on Earth have been discovered on Mars. Large amounts of frozen water were discovered at the surface, and traces of methane appeared in the atmosphere.
Three NASA missions have discovered signs of water on Mars. In 2000, Mars Global Surveyor images of gullies suggested to many that water recently flowed on the martian surface. In May 2002, the gamma ray spectrometer on Mars Odyssey found a huge deposit of hydrogen in shallow polar soil -- a sure sign of water ice. Then, in December 2004, researchers using the Mars Exploration Rover Opportunity announced that they had discovered rocks that had been formed by the periodic flooding of water on the surface. Such findings support the idea that Mars was warm and wet billions of years ago.
Post by Chicago Astronomer Joe on Aug 9, 2005 23:33:04 GMT -6
Is Methane The First Direct Sign Of Extra-Terrestrial Life?
Moffett Field CA (SPX) Aug 09, 2005 Are microbes making the methane that's been found on Mars, or does the hydrocarbon gas come from geological processes? It's the question that everybody wants to answer, but nobody can. What will it take to convince the jury? Many experts told Astrobiology Magazine that the best way to judge whether methane has a biological origin is to look at the ratio of carbon-12 (C-12) to carbon-13 (C-13) in the molecules. Living organisms preferentially take up the lighter C-12 isotopes as they assemble methane, and that chemical signature remains until the molecule is destroyed.
"There may be a way of distinguishing the origin of methane, whether biogenic or not, by using stable isotope measurements," says Barbara Sherwood Lollar, an isotope chemist at the University of Toronto.
But isotope signals are subtle, best performed by accurate spectrometers placed on the martian surface rather than on an orbiting spacecraft orbit.
* The Phoenix lander, scheduled for launch in August 2007, will go to an ice-rich region near the North Pole, and "dig up dirt and analyze the dirt, along with the ice," says William Boynton of the University of Arizona, who will direct the mission.
The lander's mass spectrometer will measure isotopes in any methane trapped in the soil, if the concentration is sufficient. "We won't be able to measure the isotope ratio [in the atmosphere], because it won't be a high enough concentration," Boynton says.
* Mars Science Laboratory, scheduled for launch sometime between 2009 and 2011, is a 3,000-kilogram, six-wheel rover packed with scientific instruments. The tunable laser spectrometer and mass spectrometer-gas chromatograph may both be able to ferret out isotope ratios of carbon and other elements.
* Beagle 3, a successor to Britain's lost-in-space Beagle 2, may carry an improved mass spectrometer capable of measuring carbon isotope ratios, but the project has yet to be approved. The craft would not launch until at least 2009.
Vladimir Krasnopolsky, who led one of the teams that found methane on the planet, says, "Bacteria, I think, are plausible sources of methane on Mars, the most likely source." But he expects the microbes to be found in oases, "because the martian conditions are very hostile to life. I think these bacteria may exist in some locations where conditions are warm and wet."
Post by Chicago Astronomer Joe on Nov 2, 2005 4:01:24 GMT -6
Methane Found In Desert Soils Bolsters Theories That Life Could Exist On Mars
Los Angeles CA (SPX) Nov 01, 2005
Evidence of methane-producing organisms can be found in inhospitable soil environments much like those found on the surface of Mars, according to experiments undertaken by scientists and students from the Keck School of Medicine of the University of Southern California and the University of Arkansas and published online in the journal Icarus. These results, they say, provide ample impetus for similar "biodetection experiments" to be considered for future missions to Mars.
"Methane-producing organisms are the ones most likely to be found on Mars," notes Joseph Miller, Ph.D., associate professor of cell and neurobiology at the Keck School and one of the study's lead researchers. "And, in fact, methane was detected on Mars last year."
Methane is considered to be a biological signature for certain living organisms that metabolize organic matter under conditions of low or no oxygen. Terrestrial methanogens (methane-producers) are typically found in environments largely protected from atmospheric oxygen, such as peat bogs, oceanic methane ices and anoxic levels of the ocean. But they had not previously been detected in an arid desert environment.
Post by Chicago Astronomer Joe on Jan 11, 2006 18:03:23 GMT -6
The forgotten methane source
In the last few years, more and more research has focused on the biosphere; particularly, on how gases which influence the climate are exchanged between the biosphere and atmosphere. Researchers from the Max Planck Institute for Nuclear Physics have now carefully analysed which organic gases are emitted from plants. They made the surprising discovery that plants release methane, a greenhouse gas - and this goes against all previous assumptions.
Methane is the greenhouse gas which has the second greatest effect on climate, after carbon dioxide. The concentration of methane in the atmosphere has almost tripled in the last 150 years. Methane is best known as natural gas, currently an important energy source. Nonetheless, only part of the methane uptake in the atmosphere is due to industrial activities connected to energy production and use. More important for the increase of methane in the atmosphere is the increase in so-called "biogenic" sources, e.g., rice cultivation or domestic ruminants related to the rise in the world's population. Nowadays, methane in the atmosphere in fact is largely of biogenic origin.
Until now, it has been assumed that biogenic methane is formed anaerobically, that is, via micro-organisms and in the absence of oxygen. In this way, acetate or hydrogen and carbon dioxide are transformed into methane; they themselves are created in the anaerobic decomposition of organic materials. The largest anoxic sources of methane are wetlands and rice fields, as well as the digestion of ruminants and termites, waste disposal sites, and the gas produced by sewage treatment plants. According to previous estimates, these sources make up two-thirds of the 600 million tonnes worldwide annual methane production.
. The researchers made the surprising discovery during an investigation of which gases are emitted by dead and fresh leaves. Then, in the laboratory and in the wild, the scientists looked at the release of gases from living plants like maize and ryegrass. In this investigation, it turned out that living plants let out some 10 to 1000 times more methane than dead plant material. The researchers then were able to show that the rate of methane production grew drastically when the plants were exposed to the sun.
The headline to this thread may be somewhat misleading. Methane (CH4) is the simplest hydrocarbon in the universe. It is produced by joining a mere five atoms from just two of the most common and easily combined chemical elements. It is readily formed through inorganic processes such as volcanism and others that are less explosive. Pasted below is a balanced article from space.com: ____________________________________
Scientists Unsure if Methane at Mars Points to Biology or Geology By Tariq Malik Staff Writer posted: 04:30 pm ET 29 March 2004
A trio of research teams independently probing the Martian atmosphere for signs of methane have found it, a combined discovery that opens the door for a host of theories as to how the gas got there.
Among the most tantalizing, if not very likely, of scenarios, scientists say, is the possibility that the Mars methane could be the byproduct of some form of microbial life. But a safer bet, they say, centers on the geology of Mars, including anything from volcanic activity to long-ago impacts of methane-carrying comets.
"It's of course very exciting and quite a surprise," said Augustin Chicarro, project scientist for the European Mars Express mission, which detected Mars methane while orbiting the planet. "Mars seems to be a planet that is always surprising us, one week it's an oceannow this."
The methane findings comes just weeks after NASA's Mars Exploration Rovers (MER) Spirit and Opportunity found conclusive evidence that water once flowed on the surface of the red planet, providing firm evidence for a location on Mars that could have supported life.
Water does not mean life, however, and neither does methane.
While not a rover itself, the Mars Express orbiter pieced together its methane picture after successive turns around the planet, detecting a small amount of the gas in the atmosphere. Two other projects, one led by NASA scientist Michael Mumma of Goddard Space Flight Center and the other by Vladimir Krasnopolosky, a researcher with the Catholic University of America in Washington, D.C., used ground-based telescopes to detect Mars methane as well.
"I would say that they confirm our results," Krasnopolosky told SPACE.com, adding that his study predicted almost the exact concentration of methane, about 10.5 parts per billion, seen by Mars Express.
Since methane has a relatively short lifetime on Mars for atmospheric gases, about 300 years or so, scientists believe there must be some process at work to keep replenishing its concentration in the atmosphere.
On Earth, methane is belched into the air during volcanic eruptions. It seeps out from fissures in the crust. And it is expelled by methanogenic bacteria as a waste product. While the idea of subterranean microbes living just under the Martian surface is attractive, Mars researchers are hesitant to put the full weight of their belief behind it.
"I think the first possibility, volcanism, is probably best," Chicarro said. "Volcanism has not been ruled out as a modern phenomena on Mars."
Nothing so explosive as an eruption is needed to expel the gas. It could possibly seep out through gentle, consistent hydrothermal activity, Chicarro said.
Krasnopolosky, on the other hand, said while he believes that Martian microbes are the most likely methane culprits, he cannot definitely rule out other factors. It is just as possible, he said, that methane formed in Martian volcanoes and outgassed through primordial surface vents, or even crashed down onto the planet during comet and meteorite impacts.
Locating the source of Mars methane could pare down at least some of those scenarios if researchers are able to determine local concentrations. Both Mars Express and Krasnopolosky's study measured Mars methane on a global scale. However, it may be possible for Mars Express researchers to use their spacecraft's mineralogical mapping instrument to scan the surface for signs of volcanic activity, then compare the results with methane observations.
In the meantime, researchers plan to continue their Mars studies.
"It seems like with every set of missions to Mars, instead of a gradual increase in our understanding we have a quantum leap," Chicarro said. "It's really a complicated place."
Last Edit: Jan 11, 2006 23:46:37 GMT -6 by Centaur