In Greek mythology, Prometheus is the Titan who stole fire from the gods and brought it to mortals for their use. He further irritated Zeus by offering the gods in settlement burnt sacrifice of the less appetizing portions of the sacrificial animals. As punishment, he was chained to a rock where a vulture would eat out his liver; it would grow back each day and the vulture would eat it again. Eventually he was freed by Heracles and returned to Olympus. As the introducer of fire and inventor of sacrifice he is seen as the patron of human civilization.
Prometheus was discovered in 1980 from Voyager photos. It is the inner shepherd satellite of the F ring. Prometheus has a number of ridges and valleys and several craters about 20 km in diameter but appears to be less cratered than the neighboring moons Pandora, Janus and Epimetheus. From its very low density and relatively high albedo, it seems likely that Prometheus is a very porous icy body. There is a lot of uncertainty in these values, however, and so this remains to be confirmed.
The 1995/1996 Saturn Ring Plane Crossing observations found that Prometheus was lagging by 20 degrees from where it should have been based on Voyager 1981 data. This is much more than can be explained by observational error. It is possible that Prometheus's orbit was changed by a recent encounter with the F ring, or it may have a small companion moon sharing its orbit.
- Orbital radius: 139,350 km
- diameter: 91 km (145 x 85 x 62)
- mass: 2.7×1017 kg
- Orbital period: 0.6130 days
- Orbital inclination: 0°