It’s entirely possible that researchers may have detected the first ever evidence of extraterrestrial life. Researchers who spent seven years studying the atmosphere of Mars say they glimpsed discrete plumes of methane gas rising from the surface of the planet in 2003, which could have been produced by bacteria living deep underground. On Earth, a class of bacteria known as methanogens breathes out methane as a waste product [The New York Times].
Before the public could get too excited, the researchers noted that that the biological explanation is just one of two possibilities–there’s also geological processes to consider. The methane could have been produced by geothermal chemical reactions involving water and heat like those in the hot springs of Yellowstone…. [N]o signs of recent volcanism, or even any hot spots, have been spotted on Mars [The New York Times], but ancient volcanic activity could have left methane deposits trapped underground, and puffs of that gas could be routinely released. Finally, the source could be a process known as serpentinisation that occurs at low temperatures and occurs when rocks rich in the minerals olivine and pyroxene react chemically with water, releasing methane [BBC News].
The 2003 plumes were spotted during the Martian midsummer on the northern half of the planet. The primary plume they found contained about 19,000 metric tons of methane, which is comparable to the methane produced at the large hydrocarbon seep Coal Oil Point in California, where underwater bacteria produce methane by processing hydrocarbons [Houston Chronicle]. As researchers report in Science [subscription required], methane quickly disintegrates under the sun’s ultraviolet radiation, so the methane detected in the Martian atmosphere must have been released shortly before scientists noted it.
As the methane was detected in midsummer, researchers are speculating that it may be a seasonal phenomenon. Some scientists consider it possible that microbes could have survived for aeons below the Martian permafrost layer, where water changes from ice into liquid. In deep canyons, or the walls of yawning craters, ice might plug fissures or pores connecting these sub-permafrost regions to the atmosphere. But the ice could disappear during spring and summer [BBC News]. However, it’s also possible that a summertime thaw is releasing methane produced by geochemical reactions.
The study was conducted with ground-based telescopes, using spectrometers that can measure gases from afar by the breakdown of signals in light [Reuters]. Researchers say the next step is to see if the methane outbursts are a regular phenomenon, and then to pinpoint one source of the jets as a possible landing spot for a future rover. NASA’s Mars Science Laboratory, which is expected to take off for Mars in 2011, may eventually be able to settle the question of whether the gas has a biological or geological origin: While it won’t be able to dig deep enough to the find the source, it will have an instrument on board that can distinguish between the two types of methane.
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Image: NASA, showing methane concentrations on Mars