PHOTOS: Spectacular Views Of The Solar System's Moons
Callisto, Jupiter's moon-Spectacular! According to NASA, it has the darkest surface of the four Galilean moons, but is twice as bright as our moon :) It is also the most heavily cratered object in the entire solar system!
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.
The relative sizes of a number of objects, including the three (known) members of Alpha Centauri triple system and some other stars for which the angular sizes have also been measured with the Very Large Telescope Interferometer (VLTI) at the ESO Paranal Observatory. The Sun and planet Jupiter are also shown for comparison ESO.