Case closed. After several decades of speculation and the gathering of imperfect evidence, Mars rover Curiosity has positively identified hundreds of meteorites found all over the Earth as Martians. The discovery is not unexpected, but it allows the science to go forward with renewed confidence in conjectures about the Red Planet. In particular, Curiosity’s findings could help scientists figure out exactly how Mars lost the vast majority of its atmosphere, why, and how long ago it happened.