One of the solar system's most evocative mysteries—the origin of Saturn's rings—may be a case of cosmic murder, new research suggests. The victim: an unnamed moon of Saturn that disappeared about 4.5 billion years ago. The suspect: a disk of hydrogen gas that once surrounded Saturn when its dozens of moons were forming, but has now fled the crime scene. The cause of death: A forced plunge into Saturn. And those spectacular and colorful rings are the only evidence left.
As the doomed moon made its death spiral, Saturn robbed its outer layer of ice, which then formed rings, according to a new theory published online Sunday in the journal Nature. A large disk of hydrogen gas circled Saturn and that helped both create and destroy moons. Large inner moons probably made regular plunges into the planet, pulled by the disk of gas. These death spirals took about 10,000 years and the key to understanding the rings' origins is what happened to them during that time. According to Canup's computer model, Saturn stripped the ice away from a huge moon while it was far enough from the planet that the ice would be trapped in a ring.