Answer: Ganymede

For the most part, moons tend to be particularly sedate celestial bodies. Most moons are typically just big hunks of cold rock with little geological activity to speak of, quietly orbiting their host planets.

In that regard, Jupiter’s massive moon, Ganymede, is distinct in two ways. First, it’s somewhat geologically active with an iron-rich, liquid core similar to Earth. Second, due to that liquid iron core, it’s the only moon in our solar system known to have a magnetic field.

As a result of the magnetic field, the thin atmosphere of Ganymede lights up with auroral displays when it is bombarded with plasma energy coming from Jupiter, just like Earth’s magnetic field interacts with solar winds to create auroras (Australis and Borealis).