NASA's Mars Rover Curiosity has just discovered methane, an organic molecule, on Mars. This is a potentially groundbreaking discovery as 95% of the methane on Earth comes from life.

CNET reports,"We think life began on Earth around 3.8 billion years ago, and our result shows that places on Mars had the same conditions at that time -- liquid water, a warm environment, and organic matter," said Caroline Freissinet of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So if life emerged on Earth in these conditions, why not on Mars as well?"

While methane is usually made by life, there are natural processes that produce it, so this is not definitive proof of live, merely evidence that allows for its possibility. At this point NASA has not determined how much methane is on Mars, merely detecting its presence. 

HNGN reports, "Ninety-five percent of methane on Earth comes from microbial organisms, so the suggestion seems valid. The source of the methane on Mars is still unknown, but possibly thought to be disturbed underground stores.

"These are molecular cages of water-ice in which methane gas is trapped," said Curiosity scientist Sushil Atreya. "From time to time, these could be destabilized, perhaps by some mechanical or thermal stress, and the methane gas would be released to find its way up through cracks or fissures in the rock to enter the atmosphere."

The team responsible for Curiosity's Sample Analysis at Mars instruments have several hypotheses besides biological processes including chemical reactions in ancient hot springs, or arrival from off planet dust through meteorites, asteroids, and comets. 

"The background figure suggests there are about 5,000 tonnes of methane in the atmosphere," said Chris Webster from Nasa's Jet Propulsion Laboratory. "You can compare that with Earth where there are about 500 million tonnes."

The search for organics on Mars has been extremely challenging for the team," said study co-author Daniel Glavin of NASA Goddard.

"First, we need to identify environments in Gale crater that would have enabled the concentration of organics in sediments. Then they need to survive the conversion of sediment to rock, where pore fluids and dissolved substances may oxidize and destroy organics. Organics can then be destroyed during exposure of rocks at the surface of Mars to intense ionising radiation and oxidants. Finally, to identify any organic compounds that have survived, we have to deal with oxychlorine compounds and possibly other strong oxidants in the sample which will react with and combust organic compounds to carbon dioxide and chlorinated hydrocarbons when the samples are heated by SAM."

Project scientist John Grotzinger said, "It's a big day for us - it's a kind of crowning moment of 10 years of hard work - where we report there is methane in the atmosphere and there are also organic molecules in abundance in the sub-surface."