A mineral called siderite found abundantly in rock drilled by a NASA rover on the surface of Mars is providing fresh evidence of the planet's warmer and wetter ancient past when it boasted substantial bodies of water and potentially harbored life.

A treasure trove of clues from Curiosity reveals that ancient Mars once trapped massive amounts of CO2 in its crust, thanks to surprising concentrations of iron carbonate deep in Gale Crater. By drilling into layers laid down in a vanished lake,