Since it landed on Mars in 2012, one of the main scientific objectives of the Curiosity rover has been finding evidence of past (or even present) life on the Red Planet. In 2014, the rover may have accomplished this very thing when it detected a tenfold increase in atmospheric methane in its vicinity and found traces of complex organic molecules in drill samples while poking around in the Gale Crater.
The surface of Mars is a cold desert. Scars in the landscape point to a history of flowing rivers, standing lakes and possibly even planetary oceans. Yet the current Martian atmosphere has a density that’s around 0.6% of Earth’s, making it far too thin to support liquid water – or life – on the barren surface.