Jupiter's Satellite Ganymede

Credit: Galileo Project, JPL, NASA

Ganymede is the largest satellite of Jupiter, and the largest known one in the Solar System. Ganymede orbits Jupiter in roughly seven days. Europa's orbits in half this time, and Io in one quarter of it. The satellites affect one another and maintain this 1:2:4 resonance in period.

Ganymede has a diameter of 5,268 km (3,273 mi), 8% larger than the planet Mercury, but since it is made of ices and rock its mass is only 45% that of Mercury. Ganymede is 2% larger than Saturn's Titan, the Solar System's second-largest satellite.