for National Geographic News
A new study of Saturn's striking rings has found clusters of "moonlets," lending support to the theory that large icy moons were slowly pulverized to form the ring system.
The boulder-size chunks, spotted in a narrow belt, could only have been formed when something collided into an object at least as large as Pan, Saturn's innermost moon, which is about 15 miles (25 kilometers) wide, scientists say.
The origin of Saturn's ring system remains a mystery. Some experts say the rings are remnants of the same gas and dust that formed Saturn.
Others support the idea that the ring's icy chunks formed from moons that were battered by asteroid impacts or blasted apart by collisions with meteors.
Unraveling the mystery of the rings' formation will help scientists better understand how our solar system—and alien ones—form.
"The origin and evolution of planetary rings is one of the prominent unsolved problems of planetary sciences," write the study authors in this week's issue of the journal Nature.
(Related: photo: "New Saturn Ring Found" [September 21, 2006].)
Encircled in Mystery
At ten times Earth's diameter, Saturn is the second-largest planet in the solar system.
Its rings are among the most beautiful features in the solar system: wide, flat discs of ice crystals that seem to float serenely in space.
The ice pieces range from the size of dust to more than ten feet (three meters) across.
For years researchers have noticed strange, paired bright streaks within Saturn's outermost ring, which is dubbed the A ring. The narrow band lies about 80,000 miles (130,000 kilometers) from the planet's surface.
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