The Martian surface

An artist's conception shows simple, translucent life-forms producing methane (blue spheres) under the Martian surface.

Recent images of Mars revealed seasonal methane plumes on the red planet, some releasing as much as 19,000 metric tons of the gas.

One theory is that active methane emissions could be signs of life on Mars—microbes deep underground could be giving off the gas as waste or using it as a food source.



Seen in a new image from NASA's Mars Reconnaissance Orbiter, channels--some new, some faint and filled in--zigzag down a dune dusted with seasonal carbon dioxide frost on Mars.

What liquid or gas carved the gullies remains a mystery.