Gannymede is the largest moon of which planet?

The story behind the answer

Ganymede is the largest moon in the solar system, and it orbits Jupiter. Discovered by Galileo in 1610, it’s one of the four Galilean moons (Io, Europa, Ganymede, Callisto) that revealed to early astronomers that not everything orbits Earth—key evidence for the heliocentric model.

Bigger than the planet Mercury, Ganymede uniquely has its own magnetic field and likely hides a global subsurface ocean beneath an icy crust. To remember it belongs to Jupiter, use the mnemonic “I Eat Green Cookies” (Io, Europa, Ganymede, Callisto) for Jupiter’s big four. As contrasts: Neptune’s largest moon is Triton, Uranus’s is Titania, and Mars’s tiny moons are Phobos and Deimos.