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Saturn's Rings: Nursery for New Moons?

Irene Klotz, Discovery News

Photos

Master Moonbuilder

Dec. 7, 2007 -- Small moons embedded in Saturn's ring system likely settled into orbit and then bulked up by absorbing bits of neighboring debris, an analysis of high-resolution imagery taken by the Cassini spacecraft shows.

The finding refines the long-held theory that the small members of Saturn's eclectic clan of satellites are shards of cosmic collisions pinned in place by the planet's gravity.

Studies of Pan, Saturn's innermost moon, and newly discovered Daphnis, a 4-mile-diameter world orbiting within Saturn's A-ring, show that they "almost certainly opened their respective gaps (in the rings) and then grew to their present size early on when the local ring environment was thicker than it is today," Carolyn Porco, head of Cassini's imaging team, wrote in today's issue of Science.

Proco, a researcher with the Space Science Institute in Boulder, Colo., and colleagues mapped the shapes and densities of more than a dozen small Saturn satellites, showing that the worlds grew as large as they could balancing the various gravitational effects. The researchers also took into consideration the diminished supply of building materials as the rings thinned out.

They found that computer models of that growth process matched the satellites' shapes better than models simulating collision forces.