Jupiter and Saturn, the two largest planets in the Solar System, are known for their large and varied systems of moons. At present count, Jupiter has more than 100 moons, while Saturn has more than double that, with over 280 known satellites. However, Jupiter's system of satellites includes four large moons - Io, Europa, Ganymede, and Callisto - and this system contains the largest moon in the Solar System (Ganymede). Meanwhile, Saturn's system of satellites is dominated by one large moon (Titan), the second largest in the Solar System.