Which Galilean moon has its own intrinsic magnetic field?

Ganymede is the Galilean moon with its own intrinsic magnetic field. The field is generated inside the moon rather than merely induced by Jupiter’s powerful magnetosphere.

NASA’s Galileo spacecraft detected Ganymede’s permanent magnetic moment during close flybys in the 1990s. Scientists believe a liquid, electrically conductive iron-rich core produces the field through convection, much as Earth’s outer core generates our planet’s magnetism.

Ganymede’s magnetic field creates a small magnetosphere embedded within Jupiter’s much larger one. Its field is relatively weak compared with Earth’s, but it is strong enough to trap charged particles and produce auroral emissions near the moon’s poles. Ganymede also has an induced magnetic component associated with Jupiter’s changing field.

A common mix-up is confusing intrinsic and induced magnetism. Europa and Callisto can develop induced magnetic fields because of electrically conductive subsurface oceans, but Ganymede is the Galilean moon known for a permanent internally generated field.