Close In

Another example of the complexities of the Saturnian system. Atlas is the closest moon to Saturn and was discovered in 1980 - from Voyager photos - and was thought to be a shepherd to the A ring, the edge of which it hugs as it travels inside the Roche Division between the main rings and the outlying F ring, but now it's known that in fact it is Janus and Epimetheus that maintain the edge of the A ring. Atlas is perturbed by the F ring shepherds, more strongly by Prometheus than Pandora, so its orbit is irregular - yet the edge of the ring, so close to the moon, is not is so perturbed. Weird and wonderful.

Check the Cassini site for details.