The moon Daphnis, which is about five miles (8 km) long, creates ripples in Saturn's rings as it orbits the giant planet in this January image from the Cassini spacecraft. The gravitational pull of Daphnis and other small moons stirs up the rings, which are quite dynamic. Collisions with ring material can shatter the small moons, but more material can coalesce to form new moons. Ring material rams into the surfaces of some of Saturn's larger moons, blasting out rock and ice which can then join the rings. Geysers on the moon Enceladus also supply an outer ring with fresh ice. [NASA/JPL/SSI]