Icy Disaster in the Kuiper Belt

A rogue ball of ice as big as Pennsylvania smashes into an Alaska-sized dwarf planet, spewing debris across the solar system and furnishing the planet with two new moons. Although it could be a disaster scene from a sci-fi movie, the event actually took place in the outer realms of our solar system a few billion years ago. "It's just a spectacular story," says planetary scientist Michael Brown of the California Institute of Technology in Pasadena, whose team has discovered the fragments of the cosmic catastrophe. What's more, the find sheds new light on the early history of our solar system.