Epimetheus and Janus: Interchangeable Moons of Saturn . ... Credit Copyright: Cassini Imaging Team , SSI , JPL , ESA , NASA Explanation: These two moons change places. Epimetheus and Janus , two small moons of Saturn , actually switch positions as they orbit their home planet. ... One moon orbits Saturn well ahead of the other, at first. ... Pictured above , the two moons were photographed rounding their orbits just outside of Saturn's F ring . ... NASA Official: Jay Norris. ...