aristarchusinexile wrote:Scientific American, May/07 - Methane on Mars and Titan - on Mars "Aquifiers below the ice would provide a habitat for creatures or a venue for the hydrochemical (Black Smokers) production of methane." Black Smokers in earth's oceans produce both methane and sustain large populations of creatures.
'On earth, 90-95 percent of methane is biologic in origin. Volcanoes contribute less than 0.2% of earth's methane, and that amount may simply be venting methane created by organisms in the past.'
''Possibilities for methane creation on Mars are low temperature serpentinization in aquifiers. (black Smokers). 'Another possibility are organisms known as methanogens which produce methane as they consume hydrogen, carbon dioxide, carbon monoxide.'
http://antwrp.gsfc.nasa.gov/apod/ap060721.html
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Methanopyrusis a genus of methanogen, with a single described species, M. kandleri. It is a hyperthermophile, discovered on the wall of a black smoker from the Gulf of California at a depth of 2000 m, at temperatures of 84-110 °C. Strain 116 discovered in black smoker fluid of the Kairei hydrothermal field, it can survive and reproduce at 122 °C. It lives in an hydrogen-carbon dioxide rich environment, and like other methanogens reduces the former to methane.>>
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The electron microscope revealed chain structures in meteorite fragment ALH84001
<<On August 6,
ALH 84001 became newsworthy when it was announced that the meteorite may contain evidence for traces of life from Mars, as published in an article in Science by David McKay of NASA.
Under the scanning electron microscope structures were revealed that may be the remains—in the form of fossils—of bacteria-like lifeforms. The structures found on ALH 84001 are 20-100 nanometres in diameter, similar in size to the theoretical nanobacteria, but smaller than any known cellular life at the time of their discovery. If the structures are really fossilized lifeforms, they would be the first solid evidence of the existence of extraterrestrial life, aside from the chance of their origin being terrestrial contamination.
Recent studies on ALH 84001 have shown that, although chances are low, eventually, Martian rocks such as ALH 84001 could actually transfer Martian life to Earth. Bacterial spores, and rock dwelling organisms are speculated to survive in space for 5 years, meaning transfer of Martian life to our planet is theoretically possible.
In September 2005, Vicky Hamilton of the University of Hawaii at Manoa presented an analysis of the origin of ALH 84001 using data from the Mars Global Surveyor and Mars Odyssey spacecraft orbiting Mars. According to the analysis, Eos Chasma in the Valles Marineris canyon appears to be the source of the meteorite.>>
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Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. They are common in wetlands, where they are responsible for marsh gas, and in the guts of animals such as ruminants and humans, where they are responsible for the methane content of flatulence. In marine sediments biomethanation is generally confined to where sulfates are depleted, below the top layers. Others are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of the earth's crust, kilometers below the surface.
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. Physical description
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Methanogens are usually coccoid or rod shaped. There are over 50 described species of methanogens, which do not form a monophyletic group, although all methanogens belong to Euryarchaeota. Methanogens are also anaerobic. Although methanogens cannot function under aerobic conditions they can sustain oxygen stresses for prolonged times.
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An exception is Methanosarcina barkeri, which contains a superoxide dismutase (SOD) enzyme and may survive longer. Some, called hydrogenotrophic, use carbon dioxide (CO2) as a source of carbon, and hydrogen as a reducing agent. Some of the CO2 is reacted with the hydrogen to produce methane, which produces an electrochemical gradient across a membrane, used to generate ATP through chemiosmosis. In contrast, plants and algae use water as their reducing agent.
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Methanogens lack a polymer that is found in the cell walls of other prokaryotes. Some methanogens have a cell wall that is composed of pseudomurein. Other methanogens that don't have a pseudomurein have at least one paracrystalline array (S-layer) which is made up of proteins that fit together like a puzzle.
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. Methanogens and environments
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Although most marine biogenic methane is the result of CO2 reduction, a small amount is derived from acetate (CH3COO-). Methanogens play the vital ecological role in anaerobic environments of removing excess hydrogen and fermentation products that have been produced by other forms of anaerobic respiration. Methanogens typically thrive in environments in which all other electron acceptors (such as oxygen, nitrate, sulfate, and trivalent iron) have been depleted.
In the deep rock they obtain their hydrogen from the thermal and radioactive breakdown of water.
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Methanogens have been found in several extreme environments on Earth - buried under kilometres of ice in Greenland and living in hot, dry desert soil. They can still reproduce from temperatures of 15 to 100 degrees Celsius.
They are known to be the most common prokaryotes archaebacteria in deep subteranean habitats.
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Live microbes making methane were found in a glacial ice core sample retrieved from three kilometres under Greenland by researchers from the University of California, Berkeley, US. Another study has also discovered methanogens in a harsh environment on Earth. Researchers studied dozens of soil and vapour samples from five different desert environments in Utah, Idaho and California in the US, and in Canada and Chile. Of these, five soil samples and three vapour samples from the vicinity of the Mars Desert Research Station in Utah were found to have signs of viable methanogens.
Some scientists have proposed that the presence of methane in the Martian atmosphere may be indicative of native methanogens on that planet.>>
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Bovine flatulence is a source of greenhouse gas and may contribute to the greenhouse effect.
Flatulence consists of gases that are produced by symbiotic bacteria and yeasts living in the gastrointestinal tract of mammals and are released through the anus. The primary constituents of flatulence are methane (produced by bacteria) and carbon dioxide (produced by yeasts), neither of which have any smell at all. The smell of intestinal gas is caused by minute quanitites of various aromatic sulfur compounds picked up by these gases further on along their way down the intestinal tract.
The gases are produced as a by-product of digesting certain types of food. Flatulence producing foods are typically high in starch, and include beans, yams, sweet potatoes, chickpeas, citrus rinds, chestnuts, broccoli, cabbage, yeast in breads, etc. In beans, the most notorious offenders in this regard, the problem seems to arise from starch molecules resistant to digestion: when the polysaccharides reach the intestines, intestinal bacteria feed on them, producing gas. In the case of those with lactose intolerance (ie. most non-Caucasian humans), intestinal bacteria feeding on lactose can give rise to excessive gas production. A European study into the effect flatulence has on general health, did not find any statistical significant differences in the general health of more flatulent and less flatulent people. They did however find that those who vented more frequently, lived significantly happier lives.
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