spacetoday.net: Moon creates "giant snowballs" in Saturn's rings

Moon creates "giant snowballs" in Saturn's rings

Posted: Wed, Jul 21, 2010, 6:42 AM ET (1042 GMT)
F-ring fan seen by Cassini (NASA/JPL)

Scientists have spotted giant "snowballs" of icy materials in the rings of Saturn created by the gravity of a passing moon. Observations by NASA's Cassini spacecraft show clumps of material forming in the planet's F ring, creating objects as large as 20 kilometers in diameter. The objects, scientists said, are created by gravitational disturbances from the moon Prometheus, one of two "shepherding" moons that keeps the narrow ring in place. Many of these objects break apart in a matter of months, but some can escape, scientists said; this may explain a small moon discovered in 2004 that intersects the ring at times, creating debris.