It has long since been a theory that the rings of Saturn are the remains of a shattered moon. What's in question is how one of the farther rings remains there since nothing seems to be keeping it there.

Objects escape their orbits depending on the circumstances. Our moon will escape the Earth's orbit someday, but it's way too big so it won't be leaving us for a few billion years. One of the farther Saturn rings, the G ring, is only made up of small particles so it should dissipate over time. But it doesn't... which brings up the question of why.

Recently the spacecraft Cassini, the same one that discovered Saturn's 60th moon, discovered what might be the source of the ring: a small portion along the inner edge of the ring is made up of chunks of debris that would form a moon about 100-meters in diameter. The debris is believed to be the remains of a dead moon. It's what feeds the G ring its supply of dust as it breaks down from being hit by micrometeorites.

Scientists also believe that the G ring's orbit around Saturn is also being maintained by one of its 60 moons, Mimas, which helps keep it in place. Scientists believe that the ring won't last very long though. Once that portion of debris runs out of particles, that's one less ring for Saturn.