Jupiter's Moon Ganymede Galileo Galilei discovered many “luminous objects” in 1610 that were orbiting Jupiter. Thought to be stars, it was discovered that they were moons: Io, Europa, Ganymede and Callisto. Ganymede is the largest moon in the Solar System and is even larger than the planet Mercury. It is the only satellite in the Solar System known … Continue reading A Moon Above the Rest: Jupiter’s Moon Ganymede →