Jupiter boasts the solar system's largest moon - Ganymede, which has a diameter of 5,268 km, making it even larger than the planet Mercury. Saturn's largest moon is Titan (5,150 km), Neptune's is Triton (2,700 km), and Pluto's largest moon is Charon (1,212 km). None of these match Ganymede's size. Jupiter's massive gravitational field allowed it to capture and retain such a large moon, making this record unique in our solar system.