In late 2013 and early 2014, NASA's Curiosity rover detected an unexpected spike in methane on Mars — 10 times the usual level. Within a few months, the spike faded. Since then, Curiosity has recorded six more of these events, but global measurements of the gas have failed to find anything conclusive.
The cause of these mysterious methane spikes may be a strange form of alien life — or it may just be interesting chemistry. Either way, something odd is happening on the Red Planet.
