The plumes of water that erupt from Saturn's icy satellite Enceladus can be traced back to a radioactive "meltdown" shortly after the moon formed. The discovery, in 2005, of water vapour spewing from geysers at Enceladus' south pole took scientists by surprise. How this tiny, ice-covered moon generated the amounts of heat needed to fuel these eruptions was a puzzle. Now scientists say a short-lived burst of radioactivity early in its history kicked off a slow cooking of its core.
water ice Moon Cassini Saturn Enceladus Voyager 2