Saturn moon may have rings

Although no one has actually seen Rhea's rings, scientists say that odd data collected during a 2005 flyby of the Cassini spacecraft provides strong clues.

"We can't say definitely that there are rings surrounding Rhea," said planetary scientist Geraint Jones.

"But the data we have are a real puzzle, and the only reasonable explanation we've been able to come up with is the debris disk proposal."

Jones, of University College London, led a study on the Cassini data to be published in tomorrow's issue of the journal Science.

Rhea sweeps through Saturn's magnetic field, which traps charged particles in a bubble zone that includes the tiny moon's orbit.

Jones' team had expected to see a dip in the amount of electrons in Rhea's wake as the surface of the 950-mile-wide (1,529-kilometer-wide) moon intercepted the particles.

The researchers also expected Cassini to find a thin halo of dust kicked up by the micrometeorites that constantly bombard Rhea's surface.

The team did detect these features, but they also found a surprise: The amount of charged particles decreased along a region extending outward on each side to about eight times the moon's diameter.