Saturn's second largest moon, Rhea, may have rings, according to images from a spacecraft managed by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Los Angeles.
The finding was described in a study published in the March 7 issue of the journal Science.
Scientists at NASA believe the rings may be the remnants of an asteroid or comet collision, which circulated large quantities of gas and solid particles around Rhea.
"Until now, only planets, not moons were known to have rings, but now Rhea seems to have some family ties to its ringed parent Saturn," said Geraint Jones, a scientist working on the Cassini space vehicle, whose magnetospheric imaging instrument may have detected at least one of the rings.
Rhea is about 950 miles (1,520 kilometers) in diameter. The particles in the disk range from the size of small pebbles to boulders. An additional dust cloud may extend up to 3,000 miles (4,800 kilometers) from the moon's center -- eight times the radius of Rhea.
Cassini scientists are working to determine whether Rhea can maintain the rings. Mathematical models show that the moon's gravitational field, and its orbit around Saturn, could allow the rings to remain in place for a "very long time," according to JPL.
"Seeing almost the same signatures on either side of Rhea was the clincher," Jones said.
"After ruling out many other possibilities, we said these are most likely rings. No one was expecting rings around a moon."
"The diversity in our solar system never fails to amaze us," said Candy Hansen, co-author and Cassini scientist.
"Many years ago we thought Saturn was the only planet with rings. Now we may have a moon of Saturn that is a miniature version of its even more elaborately decorated parent."
The discovery was a result of a November 2005 flyby by Cassini. The spacecraft's imaging instrument detected brief drops in electrons on both sides of the moon, which suggested the existence of rings.
The rings of the planet Uranus were found in a similar way by NASA's Kuiper Airborne Observatory in 1977.
Source:Xinhua
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