Jupiter spins faster than any other planet — a day is only about 10 hours long — yet it takes almost 12 Earth years to complete a single trip around the Sun. Its most famous feature, the Great Red Spot, is a storm larger than Earth that has been raging for hundreds of years.
Of Jupiter's 95 known moons, four stand out: Io, Europa, Ganymede, and Callisto — the "Galilean moons," first spotted by Galileo in 1610. Io is riddled with active volcanoes, Europa hides a vast liquid ocean beneath its ice, Ganymede is bigger than the planet Mercury, and Callisto is the most heavily cratered object in the solar system.