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Prometheus and Pandora herd the F ring (movie)

Prometheus and Pandora herd the F ring (movie)
Prometheus and Pandora herd the F ring (movie) This movie sequence from Cassini shows dark drapes in the inner strands of Saturn's F ring caused by the gravitational influence of the shepherd moon Prometheus. Prometheus appears first in the sequence, interior to the F ring, and Pandora follows along outside of the ring. Prometheus orbits closer to Saturn, and thus faster, than the icy particles that make up the F ring. The moon passes closest to the ring at "apoapse", when it is farthest from Saturn. It is during these apoapse passages that Prometheus has its greatest influence on the fine ring material. With time, the ring material previously affected falls behind so that on the next apoapse passage of Prometheus, a new gore in the inner ring material is made. The material closer to Prometheus orbits the planet faster than the material closer to the bright F ring core. The gores, together with the sheared-out material, create the dark, diagonal drapes. Visit the Planetary Photojournal to download a high-resolution, 170-frame version of this movie. NASA / JPL-Caltech / Space Science Institute