Saturn's Moon Triggers Giant Snowballs in Planet's Ring

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Saturn's Moon Triggers Giant Snowballs in Planet's Ring

Tue Jul 20, 2:36 PM

by ChowSPACE.com Staff Writer A NASA spacecraft that orbits Saturn has captured new images that show icy particles in the planet's outermost discrete ring that are clumping into giant snowballs, created by the gravitational pull of a nearby moon. The Cassini spacecraft, which has monitored collisions and disturbances in the gas giant's rings for the last six years, spotted the icy clumping process as the moon Prometheus makes multiple swings by Saturn's F ring - a thin ring orbiting about 87,000 miles (140,000 km) out from the planet. [Photo of the fan-like structures]. The moon's gravitational pull creates disturbances in the ring material, making wake channels that trigger the formation of objects as large as 12 miles (20 kilometers) in diameter, when smaller masses stick together through their mutual gravitational attraction. The natural processes that occur within Saturn's rings can give scientists a glimpse into the mechanisms at work in our early solar system, as planets and moons coalesced out of disks of debris. "Scientists have never seen objects actually form before," said Carl Murray, a Cassini imaging team member based at Queen , University of London. "We now have direct evidence of that process and the rowdy dance between the moons and bits of space debris." Murray presented the study July 20 at the Committee on Space Research meeting in Bremen, Germany. The findings were also published July 14 in the online edition of the Astrophysical Journal Letters. Saturn's F ring Saturn's relatively thin F ring was discovered by NASA's Pioneer 11 spacecraft in 1979. Prometheus and Pandora, the small moons found on either flank of the F ring, were discovered a year later by NASA's Voyager 1 robotic space probe. In the years since its discovery, the F ring has undergone constant changes in appearance, and scientists have closely monitored the behavior of the two mischievous moons for answers. Prometheus, which is larger and closer to Saturn, appears to be the main source of the disturbances in the F ring. At its longest point, the potato-shaped moon is 92 miles (148 km) across. This moon swerves around Saturn at a speed slightly greater than the speed of the much smaller particles in the planet's F ring. As a result of this discrepancy, and the slightly offset orientation of Prometheus' orbit, the moon laps the F ring particles, stirring them up approximately every 68 days.

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