why are three saturn's satellites atlas prometheus and pandora called shepherd moons
Saturn has a number of shepherd moons. They are so called because they deflect material trying to leave the ring back into place. They are responsible for the gaps in the rings. Prometheus and Pandora both orbit close to the F ring. Prometheus is known to act as a shepherd for the outer edge of the F ring and Pandora for the inner edge of the F ring. Atlas was thought to be the shepherd for the outer edge of the A ring but it is now known that the shepherds are Janus and Epimetheus.