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
, but ancient volcanic activity could have left methane deposits trapped ...
