writes "For the first time ever, astronomers have witnessed the formation of celestial objects... in Saturn's rings. As the Saturnian moon Prometheus dashes through the gas giant's rings, it leaves large formations of ice behind, some as large as 12 kilometers in diameter. When the small moon makes another pass, it is not known whether these giant 'snowballs' remain or get destroyed, but according to Linda Spilker, from NASA's Jet Propulsion Laboratory: 'You can think of Saturn's rings as miniature versions of the disks where planets form. The same physical processes are occurring.'"
The Planetary Society blog has further explanation, as well as pictures and a movie of Prometheus' interaction
with Saturn's rings. The Cassini team has released some fantastic images of the fans
in the F ring, as well as a simulation showing how the ring's particles are affected by the moon's passing