Ganymede is the largest natural satellite of Jupiter and the Solar System, as well as being the only one with a magnetic field. Was discovered on January 7, 1610 by Galileo Galilei junto a las otras lunas galeleanas. In order of distances to the planet, it is the seventh closest and the third of the Galileans. It completes its orbit in about 7 days and maintains an orbital resonance with Io and Europa of 1:2:4. Its diameter is 5,268 km, 8% greater than that of Mercury, although it only represents 45% of its mass. It is 2% greater than Titan, the second largest natural satellite, and twice as massive as the Moon. In absolute terms, it is the ninth largest object in the Solar System and the largest without a significant atmosphere.
