Scientists have found evidence for small moonlets within Saturn’s rings. The moons, estimated to be about 300 feet in diameter, are as yet unseen, but they produce strange propeller-shaped disturbances in the ring matrix. First estimates suggest there could be at least ten million of these bodies in the rings.
If a moon is big enough, like Pan here (below) its gravity is ample enough to clear out a path in the ring system. The Encke Gap was first observed on Earth in the 1830′s. The moon was discovered a century and a half later. In fact, scientists first saw the moon while examining nine-year old Voyager images in 1990.