[sevnson_71]

By Azadeh Ansari
CNN(CNN) -- Scientists have discovered methane in Mars' atmosphere, raising the possibility that life might exist on the planet.

The methane could have come from past or present subsurface microorganisms, geological activity or comets striking the planet, scientists and NASA officials said. Scientists were not sure how long the methane has been on the planet.

Methane -- four atoms of hydrogen bound to a carbon atom -- is the main component of natural gas on Earth. It's of interest to astrobiologists because organisms release much of Earth's methane as they digest nutrients. Other purely geological processes, like oxidation of iron, also release methane.


Full Story