The largest moon in our solar system is Ganymede, a natural satellite of Jupiter. Ganymede has a diameter of about 5,270 kilometers (3,275 miles), making it even larger than the planet Mercury. It is not only the biggest but also the most massive moon in the solar system. Ganymede is unique in having its own magnetic field, and it possibly harbors an underground ocean that contains more water than all of Earth's oceans combined.
