Jupiter's Moons: Four Largest

Callisto

Callisto, or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System after Ganymede and Saturn's largest moon Titan, and the largest object in the Solar System that may not be properly differentiated. Callisto was discovered in 1610 by Galileo Galilei.

Europa

Europa, or Jupiter II, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet of all the 79 known moons of Jupiter. It is also the sixth-largest moon in the Solar System.

Ganymede

Ganymede, a satellite of Jupiter, is the largest and most massive of the Solar System's moons. The ninth-largest object in the Solar System, it is the largest without a substantial atmosphere.

Io

Io, or Jupiter I, is the innermost and third-largest of the four Galilean moons of the planet Jupiter. It is the fourth-largest moon in the Solar System, has the highest density of all of them, and has the lowest amount of water of any known astronomical object in the Solar System.