Which moon of Jupiter is the largest in the solar system?

Ganymede is the largest moon in the Solar System. It orbits Jupiter and measures about 5,270 kilometers across, making it larger in diameter than the planet Mercury, although it has only about 45% of Mercury's mass.

Ganymede is also the Solar System's most massive moon. Its interior appears differentiated into an iron-rich core, a rocky mantle, and outer layers containing water ice and liquid water. Observations of its auroras and magnetic environment provide evidence for a salty subsurface ocean.

Galileo Galilei and Simon Marius observed Ganymede in 1610. Galileo's telescopic discovery of bodies orbiting Jupiter helped challenge the old idea that everything in the heavens revolved around Earth. The moon's name comes from Ganymede, a figure in Greek mythology associated with Zeus.

The most tempting wrong answer is Titan, Saturn's largest moon. Titan has a thick atmosphere and is the second-largest moon, but Ganymede is larger. Callisto and Europa are also among Jupiter's Galilean moons, yet neither matches Ganymede's size.