LARGER than Mercury and Pluto, and only slightly smaller than Mars. Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun.Jupiter currently has 79 KNOWN satellites. Uranus currently has 27 known satellites.Neptune has 14 known MOONS, which are NAMED for minor water deities in Greek mythology.Saturn has 82 moons.