spacetoday.net: Cassini reveals Phoebe from Kuiper Belt

Posted: Sat, Jun 26, 2004, 1:03 PM ET (1703 GMT)
Phoebe image from Cassini (NASA/JPL)

Analysis of data collected by the Cassini spacecraft when it flew past the outer Saturnian moon of Phoebe earlier this month have led scientists to conclude that the moon was a Kuiper Belt object captured by the planet. Scientists have determined that Phoebe's surface is largely a mix of water ice, water-bearing minerals, carbon dioxide, and some organic materials, a composition that suggests to them that Phoebe is a primordial object dating back to the formation of the solar system four and a half billion years ago. Phoebe likely formed at about this distance from the Sun, as was the case for Kuiper Belt objects, but was captured by Saturn's gravity rather than being swept out into the outer solar system. The moon's density suggests that while its outer layers are icy, it may have a rocky interior, like larger bodies, such as Triton and Pluto. Cassini remains on track to enter orbit around Saturn on the night on June 30.