Epimetheus

Epimetheus is an inner satellite of Saturn. It is also known as Saturn XI. It is named after the mythological Epimetheus, brother of Prometheus.
Epimetheus occupies essentially the same orbit as the moon Janus. Astronomers assumed that there was only one body in that orbit (disbelieving that two moons could share nearly identical orbits without colliding), and accordingly had difficulty determining their orbital characteristics. Observations were photographic and spaced widely apart in time, so that while the presence of two objects was not obvious, the observations were difficult to reconcile with a reasonable orbit.
== Orbit ==
Epimetheus's orbit is co-orbital with that of Janus. Janus's mean orbital radius from Saturn is, as of 2006, only 50 km less than that of Epimetheus, a distance smaller than either moon's mean radius. In accordance with Kepler's laws of planetary motion, the closer orbit is completed more quickly.
== Physical Characteristics ==
Epimetheus has several craters larger than 30 km in diameter, as well as both large and small ridges and grooves. The extensive cratering indicates that Epimetheus must be quite old. Janus and Epimetheus may have formed from a disruption of a single parent to form co-orbital satellites, but if this is the case the disruption must have happened early in the history of the satellite system. From its very low density and relatively high albedo, it seems likely that Epimetheus is a very porous icy body. There is considerable uncertainty in these values, however, and so this remains to be confirmed.
== Interactions with Saturn's Rings ==
A faint, dusty ring is present around the orbits of Janus and Epimetheus, possibly meaning debris from the moons is forming a thin ring.
Category:Moons
Category:Saturnian Moons
Category:Shepherd Moon
Category:Objects with No Atmosphere
Category:Objects Not in Hydrostatic Equilibrium
Category:Co-orbital Moon
Category:Prograde Satellite
Category:Outer Solar System Object
Category:Named Objects
Category:Named Moons
Category:Numbered Objects
Category:Numbered Moons
Category:Objects Visited by Spacecraft