Which physical characteristic is unique to Ganymede among the Galilean moons?
Answer
Possesses its own magnetic field
Ganymede stands out because it is the only moon within the entire group, and indeed, the only known moon in the Solar System, that generates its own intrinsic magnetic field. This magnetosphere is usually a characteristic associated with full-fledged planets, such as Earth. The existence of this magnetic field strongly implies that there must be a layer of liquid, electrically conductive material—likely liquid iron or perhaps sulfur—circulating deep within Ganymede's core, which is responsible for generating the magnetosphere through dynamo action. This feature complicates its internal structure assessment compared to its neighbors.
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