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Mars is a little bit "gassy."
Instruments on the ground and in space have detected small amounts of methane in the planet's atmosphere. The source of that gas is a subject of intense debate, because it could come from living organisms.
Most of the methane in Earth's atmosphere is produced by bacteria in the intestinal tracts of animals like cattle, pigs, and even people. So it's possible that even the tiny amounts of methane found in the atmosphere of Mars could also come from bacteria.
Bacteria aren't the only source of methane, though. It can also be belched out by volcanoes or other chemical reactions.
And here on Earth, some methane comes from deposits that are locked in cages of ice at the bottom of the oceans. If the ice melts, the methane is released into the water, where it can percolate up into the atmosphere. Mars doesn't have oceans, of course, but similar deposits could be buried beneath the orange Martian soil, and burp out into the atmosphere under certain conditions.
The methane in these deposits on Earth originally came from living organisms, so deposits on Mars could mean that bacteria once lived on the planet, even if there's no life there today.
Mars is low in the east at first light, and looks like a fairly bright orange star. It's almost directly above a slightly brighter orange dot -- Aldebaran, the "eye" of Taurus, the bull. Watch them over the next couple of weeks, as Aldebaran climbs past the gassy planet.
Script by Damond Benningfield, Copyright 2011