Saturn's Rings
When Saturn's rings were first examined close-up by the Voyager missions in the 1970s, it was concluded that they had formed relatively recently (like 100 million years ago) when a moon of Saturn was destroyed in a collision with another moon or an asteroid. But the latest evidence from the Cassini mission indicates that Saturn may have had similar rings since the formation of the solar system 4.5 billion years ago. However, it appears that material in the rings is continually accreting into new moonlets, only to be destroyed again in later collisions.
