Janus is quite similar to Epimetheus. Both moon share the same orbit and trade places with each other every four years. Janus is heavily cratered and likely very ancient.
A Tour of the Moons of Saturn – Janus
Published.
Frontier Channel
News and commentary about the Great Frontiers
Image Credit: ISS007-E-10807 (21 July 2003) – Earth Science and Remote Sensing Unit, NASA Johnson Space Center