This natural satellite was first identified by Audouin Dollfus on December 15, 1966, although it had been unknowingly photographed earlier by Jean Texereau.

Further observations led to the realization that Janus shares a unique orbital relationship with another moon, Epimetheus.

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

[17] 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.

Janus has a very low density and relatively high albedo, meaning that it is likely icy in composition and structurally a rubble pile object.

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

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

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