While Io, the most volcanically active moon in the solar system, appears completely dry and devoid of water ice, its neighbor Europa is thought to harbor a vast global ocean of liquid water beneath its icy crust. A new international study co-led by Aix-Marseille University and Southwest Research Ins titute (SwRI) reveals that this striking contrast was established at birth, as they formed around Jupiter, not from later evolutionary processes. ...read more read less