Epimetheus is an inner moon of Saturn. It was discovered
in 1980 from photos taken by Voyager 1 and is also known as Saturn XI.
|Epimetheus taken on Mar. 30, 2005
by Cassini from a distance of 74,782 km
|South polar region of Epimetheus taken on Dec. 3,
2007 by Cassini from a distance of 37,400 km. The view shows what
might be the remains of a large impact crater covering most of this
face, and which could be responsible for the somewhat flattened shape
of the southern part of Epimetheus. Also visible are two types of
terrain: darker, smoother areas, and brighter, slightly more yellowish,
fractured terrain. One interpretation of this image is that the darker
material evidently moves down slopes, and probably has a lower ice
content than the brighter material, which appears more like bedrock.
Nonetheless, materials in both terrains are likely to be rich in water
Epimetheus is located between the F- and G-rings (see Saturn
rings) and shares the same orbit as Janus.
Normally separated by about 50 km, every 4 years these two satellites approach
each other, exchange a small amount of momentum, and swap places. It is
possible that they formed from the break-up of a single parent object.
The surface of Epimetheus reveals a number of valleys, grooves, and ridges,
and extensive cratering, with several craters more than 30 km (19 miles)
||1980, R. Walker et al,
Voyager 1 data
||151,410 km (94,110 miles)
||135 × 108 × 105 km
(89 × 67 × 65 miles)
||0.032 km/s (115 km/h, 72 mph)
||0.694 days (16 hr 39 min)
||0.694 days (synchronous)