Figure 7-26 The F Ring and One of Its Shepherds Two tiny satellites, Prometheus and Pandora, each measuring about 50 km (31 mi) across, orbit Saturn on either side of the F ring. Sometimes the ringlets are braided, sometimes parallel to each other. In any case, the passage of the shepherd moons causes ripples in the rings, which lead to the formation of large snowballs in them. The gravitational effects of these two shepherd satellites confine the particles in the F ring to a band about 100 km (62 mi) wide.