Methane in the Martian atmosphere hints at microbial metabolism | fr584's Blog

In 2004 three groups - using telescopes on Earth and the European Space Agency's Mars Express orbiting space probe - independently turned up evidence of methane in the atmosphere. Nearly all methane in our own atmosphere is produced by bacteria and other life.

Methane could also be generated by volcanism, the thawing of frozen underground deposits, or delivered by comet impacts. However, the source has to be recent, as the gas is rapidly destroyed on Mars or escapes into space.

In January 2005, an ESA scientist controversially announced that he had also found evidence of formaldehyde, produced by the oxidation of methane. If this is proved it will strengthen the case for microbes, as a whopping 2.5 million tonnes of methane per year would be required to create the quantity of formaldehyde postulated to exist.

There are ways to confirm the presence of the gas, but scientists will need to get the equipment to Mars first.