In 2009, scientists announced that they had detected large amounts of methane on Mars. NASA’s Curiosity rover found little evidence to back up those claims after its landing in 2012. But in late 2013 and early 2014, the rover detected a 10-fold spike in the amount of methane in its vicinity. This planetary “burp,” along with the discovery of the first Martian organics, are helping scientists piece together an increasingly detailed picture of early Mars. John Grotzinger, the NASA Curiosity rover’s chief scientist, talks about what these new findings might mean for life on Mars.