[7] Twelve years later, in October 1978, Stephen M. Larson and John W. Fountain realised that the 1966 observations were best explained by two distinct objects (Janus and Epimetheus) sharing very similar orbits.

[12] This was confirmed in 1980 by Voyager 1,[13] and so Larson and Fountain officially share the discovery of Epimetheus with Walker.

The timing and magnitude of the momentum exchange is such that the moons effectively swap orbits, never approaching closer than about 10,000 km.

The orbital relationship between Janus and Epimetheus can be understood in terms of the circular restricted three-body problem, as a case in which the two moons (the third body being Saturn) are similar in size to each other.

A faint dust ring is present around the region occupied by the orbits of Epimetheus and Janus, as revealed by images taken in forward-scattered light by the Cassini spacecraft in 2006.

[20] Its source are particles blasted off their surfaces by meteoroid impacts, which then form a diffuse ring around their orbital paths.

[21][22] Along with Janus, Epimetheus acts as a shepherd moon, maintaining the sharp outer edge of the A Ring in a 7:6 orbital resonance.

[16] This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.