Saturn's "Flying Saucer" Moons Made Mainly of Ring Dust

Brian Handwerk
for National Geographic News
December 6, 2007

A new glimpse of two of Saturn's tiny moons has scientists rethinking how those satellites were created.

Once thought to be solid chunks of long-gone, larger bodies, the moons Pan and Atlas may actually be largely composed of dust and debris that has accumulated over millennia, new studies say.

This new origin theory would explain the moons' "flying saucer" shapes and perhaps shed new light on how Saturn's rings formed.

"Those little satellites that are embedded in the rings, we think, are the clues to understanding the origins of the rings," said Sébastien Charnoz, a planetary scientist with France's National Center for Scientific Research.

(Related: "Moonlet Study Sheds Light on Origins of Saturns Rings" [October 24, 2007].)

Explosive Start

In the early 1980s the Voyager 1 and 2 spacecraft revealed that several small moons orbit within Saturns rings. The discovery fueled speculation that the moons and rings were born of some violent ancient collision, or collisions.

Such a crash might have blasted ancient, larger moons or other bodies into fragments, creating the dust-and-debris fields that make up Saturn's rings.

The origins of the small moons, though, may not be quite so simple, according to two studies to be published in the journal Science tomorrow—one of which Charnoz authored.

As Charnoz explained it, larger chunks from the collision may well have become moons, while smaller ones became the rocky remnants that make up what look to us like flat rings.

But the two new studies show that the small moons may have drawn dust and debris to themselves, slowly expanding their size over millennia, he said.

Porous, "Flying Saucer" Moons

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