The Curiosity rover has looked for methane on the Red Planet and has found none, disappointing hopes for finding life—Earth’s main source of methane—on Mars.
Researchers had good reasons to pin their hopes for Martian life on methane. On Earth, living things, such as methanogenic microbes, wetlands, and cattle, release vast quantities of the stuff. Researchers thought that any methane found on Mars might have come from a living thing, too. Plus, in Mars’ atmosphere, methane would dissipate quickly, so any that they did find was likely to be fresh and might even indicate that its Martian producer was still alive.
An image of the Martian surface from NASA’s Viking 2
To eke out even the barest subsistence on Mars, a living thing would have to adapt to a formidable set of environmental challenges: an arid, often extremely cold landscape with miniscule amounts of oxygen in the atmosphere and no organic matter to eat. During a recent foray into a similarly inhospitable part of our own planet, scientists have discovered several species of bacteria that hint at what life on Mars, if it exists, might look like. These microbes survive on minerals in the surrounding rocks—minerals also found in the Martian surface.
What’s the News: On Friday, after five years of deliberation over 100 candidates, NASA announced its choice of landing site for Curiosity, the next Mars rover: Gale crater, a massive pit with a three-mile-high mound in its center. The mission’s primary goal is to assess whether conditions suitable for microbial life ever existed on the Red Planet; Gale was selected over the three other finalists in part because its mountain promises access to layered sediments extending deep into the Martian past.