Ganymede's unique magnetic field may be powered by ongoing core formation—not a cooling core‎

Ganymede is not only Jupiter's largest moon, but also the largest in our solar system and one of the few that hosts a massive ice ocean. Adding to this planet-like moon's uniqueness is the fact that among the hundreds of moons in our solar system, Ganymede is the only one that generates its own magnetic field. While the prevailing view was that Ganymede generates this magnetic field through convection in an already-formed core, there are still uncertainties surrounding this idea.