Which Saturnian moon helps Pandora shepherd the planet’s narrow F ring?

Prometheus helps Pandora shepherd Saturn’s narrow F ring.

Prometheus is an inner moon of Saturn, and Pandora is an outer moon of the F ring. Their combined gravitational effects help confine and shape the ring, which is one of Saturn’s most delicate and dynamically active ring structures. The two moons are therefore called shepherd satellites.

Voyager 1 images revealed Prometheus and Pandora in 1980. Prometheus is considerably more elongated and irregular than many larger spherical moons, and its gravity can create disturbances and streamers in nearby ring material. Pandora also influences the ring from the outside, making the pair an important example of moons controlling ring structure.

Janus and Epimetheus are another unusual pair in the Saturn system, sharing closely related orbits, but they are not the standard answer to the F-ring shepherd question. Atlas is associated with Saturn’s A ring, while Mimas is a much larger moon known for its prominent Herschel crater.