Spacecraft have been both finding and not finding methane around Mars for years. (Credit: ESA/ATG medialab)

Last week, NASA’s Mars Curiosity rover detected a sudden spike in methane levels, which kickstarted excitement about the prospects of life on the Red Planet.

On Earth, the most common source of methane is biological organisms, from cows and humans down to single-celled creatures, making its detection on the Red Planet a reason for excitement and intrigue. But it’s quite possible to