Cannibalistic Jupiter ate its early moons

The four giant "Galilean" moons orbiting Jupiter are the last survivors of at least five generations of moons that once circled the gas giant. "All the other moons - and there could have been 20 or more - were devoured by the planet in the early days of the solar system," says Robin Canup of the Southwest Research Institute in Boulder, Colorado. The four Galilean moons have played a key role in the history of science - their discovery by Galileo 400 years ago provided irrefutable evidence that not all bodies orbited the Earth. But until recently, nobody had suspected that Jupiter had once had many more moons."