Prometheus acts as a shepherding moon, constraining the extent of the inner edge of Saturn's F Ring. Prometheus is extremely irregular and has visible craters -- some up to 12.4 miles (20 km) in diameter. However, it is much less cratered than its nearby neighbors Pandora, Janus and Epimetheus. The density of Prometheus has been estimated to be low; it is probably a porous, icy body.

The potato-shaped moon is about 26.8 miles (43.1 km) in mean radius, orbiting Saturn at a distance of 87,000 miles (139,000 km), taking 14.7 hours to go around the planet.