"Pinball" Collisions Seen in Saturn Ring

Richard A. Lovett
for National Geographic News
June 4, 2008
Small moons within one of Saturn's faintest rings may occasionally collide with other large ring particles on a near-daily basis, a new study suggests.

Scientists tracked the pinball-like action by looking at changing patches of dust in Saturn's active F ring, which was discovered in the late 1970s.

The ring is patterned with twisted braids and a spiral structure, thanks in part to interactions with two small, nearby moons, Prometheus and Pandora.

"The F ring has fascinated me ever since I saw the Voyager 1 images back in 1980," said study lead author Carl Murray of Queen Mary, University of London.

Murray and his team used the Cassini spacecraft to capture the most recent images.

"One of the reasons I got involved in Cassini was to try to understand this bizarre ring," he added by email.

How Saturn's ring system formed remains a mystery. The rings could be remnants of the same gas and dust that formed Saturn, some experts say.

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

Digital Mosaics

Murray's team pieced together digital images to create 360-degree mosaics of the entire ring over time.

In November 2006, he said, the ring was relatively quiet. But in late December, a three-mile-long (five-kilometer-long) object known as S/2004 S 6—or possibly another object on a very similar orbit—appears to have begun passing repeatedly through the core of the ring.

That caused a series of collisions, producing numerous bright "jets" of material.

(Related photo: "Monster 'Hurricane' Spotted on Saturn" [November 13, 2006].)

"We could follow these for months as S 6 worked its way around the F ring," Murray said.

All of that dust also allowed the scientists to spot gravitational perturbations caused by other hidden moonlets, Murray said.

"There are still plenty of things we need to understand about the F ring," he said.

"However, we now think that we understand the basic processes that give rise to the various structures that we see."

The study appears tomorrow in the journal Nature.

(See photos of Saturn.)

Planet-Birth Insight

Other scientists are pleased with the finding.

Carolyn Porco, leader of the Cassini imaging team, was not directly involved in the new study.

"It demonstrates what's great about being in orbit and having the leisure to come back for a second look," Porco said in an email.

Larry Esposito is a planetary scientist at the University of Colorado, Boulder, who also was not involved in the study. He added by email that the new find helps scientists understand what happens in planet-forming disks around young stars.

"The processes occurring today in Saturn's F ring are like those that created the Earth and other planets."

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