{ Moons of Saturn }
Discovered by            Audouin Dollfus  
Date of Discovery        1966
Distance from Saturn     151,472 km
Radius                   97.0 × 95.0 × 77.0 km
Mass                     1.92 × 10^21 g
Orbital Eccentricity     0.007
Orbital Inclination      0.14°
Orbital Period           0.6945 day
Rotational Period        Synchronous
Density (gm/cm3)         ??? 

Janus and Epimetheus may have been part of the same body at one time. They share nearly the same orbit, but unlike co-orbital moons like Rhea and Diomed, their orbit is not stable. In fact, about once every four years they switch places, one being slightly higher than the other. Janus is heavily cratered so if it and Epimetheus were truly once a single entity, the event causing the split must have happened early in its history, billions of years ago. It is irregularly shaped, but unlike Epimetheus, it has no significant ridges, fissures, or grooves.