how big is ganymede
Ganymede Jupiter III Taking a new step...is what people fear most. - Dostoyevski. Ganymede [GAN-ee-meed] is the largest moon of Jupiter and is the largest in our solar system with a diameter of 5,262 km (3,280 miles). If Ganymede orbited the Sun instead of Jupiter it could be classified as a planet. Like Callisto, Ganymede is most likely composed of a rocky core with a water/ice mantle and a crust of rock and ice. Its low density of 1.94 gm/cm 3, indicates that the core takes up about 50% of the satellite's diameter.