In Eight Days the space craft Cassini-Huygens: Exploring Saturn's System will

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13. And still producing new data: Cassini hints at young age for Saturn's rings

The spectacular rings of Saturn may be relatively young, perhaps just 100 million years or so old.

This is the early interpretation of data gathered by the Cassini spacecraft on its final orbits of the giant world.
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This includes making a detailed map of the gravity field in which the contributions from the huge world and the rings can be teased apart.
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The more massive they are, the older they are likely to be. Some scientists think they could even have formed with Saturn itself 4.6 billion years ago. They would certainly need a large mass to withstand the forces that might erode them over time, such as collisions from tiny meteoroids. But it is looking like the opposite may actually be true - that their mass is less than previously estimated.

http://www.bbc.co.uk/news/science-environment-41091333