From : wikipedia - * Callisto * - Callisto is another of Jupiter's moons and one of the four Galilean moons. It is the third-largest moon in the Solar System and the second-largest in the Jovian system, after Ganymede -
Ganymede A satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively.