spacetoday.net: Saturn rings may be remnant of large moon

Posted: Tue, Dec 14, 2010, 6:42 AM ET (1142 GMT)
Cassini image of Saturn from February 2004 (NASA)

Saturn's icy rings may be the remnant of a large moon that collided with the planet early in its history, scientists reported this week. Computer models show that the formation of the rings, comprised almost entirely of water ice, can be explained by a Titan-sized moon spiraling in towards Saturn. Tidal heating would cause the moon to differentiate, creating an icy mantle and rocky core. Tidal forces eventually stripped those icy outer layers off before the moon collided with the planet, creating the raw material that later spread out and formed the planet's rings. This approach better explains the composition of the rings than past explanations, where a comet collided with a smaller satellite; that would create a larger fraction of rocky material in the rings than has been detected.