Jupiter’s four biggest moons are very different worlds
Diameter 3,660km Mass 0.015 Earth masses Orbital distance 421,700km In brief Io, the closest moon to Jupiter, has over 400 volcanoes across its surface. The gas giant’s constant gravitational tugging keeps its interior molten.
Diameter 3,122km Mass 0.008 Earth masses Orbital distance 670,900km In brief The smallest of the moons, Europa is covered in a thick layer of ice. Beneath this is a liquid water ocean that could be hospitable to life.
Diameter 5,268km Mass 0.025 Earth masses Orbital distance 1,070,400km In brief The largest moon in the Solar System. It is thought to have a large rocky core covered with layers of ice and water which show signs of tectonic activity.
Diameter 4,821km Mass 0.018 Earth masses Orbital distance 1,882,700km In brief The least active of the Galilean moons. Its ancient surface is almost completely covered in craters, so every new crater erases an older one.