Ganymede’s hidden heat may power a late-forming magnetic dynamo

New Science Advances study suggests Jupiter’s moon Ganymede could have formed a metal core later than previously thought and still sustain a magnetic field via a warming-driven dynamo powered by protracted core formation, radioactive heating, and tidal forces. This challenges the idea that dynamos always originate early and cool over time, and implies Ganymede’s magnetism—potentially active today—arises from a “warm start” process that could influence how we think about magnetic fields on other worlds, including exoplanets.