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, said a spokesman for Nasa.