This image provided by NASA, taken Oct. 6, 2004, by the Cassini Saturn Probe, shows the planet Saturn and its rings. One of the most evocative mysteries of the solar system, where Saturn got its stunning rings, may actually be a case of cosmic murder with an unnamed moon of Saturn, that disappeared about 4.5 billion years ago, as the potential victim. Suspicion has fallen on a disk of hydrogen gas, that surrounded Saturn when its dozens of moons were forming, but has now fled the scene. And the cause of death? A possible forced plunge into Saturn. (AP Photo/NASA)

This image provided by NASA, taken Oct. 6, 2004, by the Cassini Saturn Probe, shows the planet Saturn and its rings. One of the most evocative mysteries of the solar system, where Saturn got its stunning rings, may actually be a case of cosmic murder with an unnamed moon of Saturn, that disappeared about 4.5 billion years ago, as the potential victim. Suspicion has fallen on a disk of hydrogen gas, that surrounded Saturn when its dozens of moons were forming, but has now fled the scene. And the cause of death? A possible forced plunge into Saturn. (AP Photo/NASA)