Saturn's rings, artwork. These rings extend outwards from Saturn for around 120,000 kilometres. The rings are only about one kilometre thick, consisting of millions of chunks of rock and ice. The Cassini division in the rings is the largest gap seen here. The rings are thought to have formed from the disintegration of a moon that was too close to Saturn or was hit by a comet or asteroid. Saturn, the sixth planet from the Sun (upper right) is a gas giant of hydrogen and helium. Titan (left of Sun) is the largest of Saturn's moons. The thin outer F-ring has two 'shepherd' moons (barely visible at lower right).