Saturn's Old Rings

Astronomers have long believed the rings of Saturn, and other planets, constitituted transitory features. Using Voyager data, they thought the rings were about 100 million years old, formed perhaps when two large bodies-- say an asteroid and a moon of Saturn-- collided. Under that theory, the ring system will eventually collapse, and it was sheer serendipity that Saturn had rings when humans developed telescopes and spacecraft.

A new view seems to be emerging from Cassini data, however. Observations made by the probe in the ultraviolet suggests the ring system is much older than expected, and may even date back to the formation of the planet itself. A recycling process seems to be at work, maintaining the rings over the long term.

If the new theory is correct, whether it applies to the less spectacular rings of Jupiter and Urnanus is not clear. We shouldn't be surprised, however, if Nature has more than one way to produce planetary rings.