Ganymede’s secret core may still be forming after billions of years

A new study suggests Jupiter’s moon Ganymede could still be differentiating its metallic core billions of years after formation, with iron–sulfur melt slowly feeding a protocore that powers a long‑lived magnetic dynamo and likely an ocean beneath its ice. If correct, this ongoing core growth could explain why Ganymede remains magnetically active while other moons fade, and future missions like JUICE may test the idea.