
Ganymede’s Forming Core Sparks a New Dynamo Theory
A Science Advances study suggests Ganymede’s metallic core is still forming today, and that ongoing convection in this migrating, hot iron core powers its long-unique magnetic field via a ‘cold-start’ dynamo; the results don’t fully overturn older theories, but they offer a new mechanism to explain why Ganymede’s dynamo persists while Callisto shows no obvious one, with implications for Europa and future data from Europa Clipper and Juice.













