Good news for future space colonists: Saturn's icy moon, Dione, contains a thin layer of oxygen that hints at life on other gas giant satellites, the BBC reports. Spotted by the Cassini spacecraft about two years ago, Dione's oxygen layer lacks the necessary density to support life and is too thin to be called an atmosphere—scientists prefer "exosphere." But the discovery tells us that oxygen is common in Saturn's system and "it can come from a process that doesn't involve life," a scientist tells Space.com.
Other satellites orbiting Saturn and sister gas giant Jupiter may, however, support life and liquid oceans, scientists say. Dione's sister moon Enceladus is probably hiding an ocean under its icy surface, and Jupiter moons Europa, Callisto, and Ganymede may harbor liquid water as well. "These are fascinating places to look for signs of life," says British scientist Andrew Coates. Nearby satellite Titan, Saturn's biggest, has an atmosphere resembling that of early Earth: "It may be an Earth waiting to happen as the outer Solar System warms up," says Coates.