spacetoday.net: Cassini reveals icy nature of Phoebe

Posted: Tue, Jun 15, 2004, 8:27 AM ET (1227 GMT)
Phoebe image from Cassini (NASA/JPL)

Cassini images of Phoebe, an outer moon of Saturn, reveal that the Moon is likely an icy body that formed in the outer solar system and was later captured by Saturn, scientists said Monday. Images of the moon suggest to planetary scientists that the moon is made of "ice-rich" material, covered by a layer of darker material 300-500 meters thick. Scientists reached that conclusion based on differences in features seen on Phoebe versus similarly-sized rocky bodies, such as the asteroids Ida, Mathilde, and Eros. If Phoebe contains significant amounts of ice, it would likely mean that Phoebe formed in the outer solar system, perhaps in the Kuiper Belt, and was later captured by Saturn when it passed close to the giant planet.