Ganymede (moon)
Ganymede[p]  is the largest of over 66 moons of the planet Jupiter. It is also the largest moon in the Solar System. Ganymede is larger in diameter than the planet Mercury, but has only about half of its mass. Ganymede is much less dense. Ganymede is part of a group called the Galilean Satellites. These also include Io, Europa and Callisto.