Ganymede is a moon that orbits the planet Jupiter, which in turn orbits Sol in the Spore Galaxy. While Ganymede is the only moon that orbits Jupiter in Spore, many more orbit Jupiter in real life. This is due to the game mechanics, as no planet has more than one moon in game. Ganymede cannot be seen on the planet identifying box that appears above stars while in the galaxy view.
It is either a Rocky planet, a Flurry planet, or rarely, an Arid planet and holds either Yellow or Purple Spice, which can be harvested by the player if terraformed. The moon has no life, unless terraformed and seeded with life.