Scientists spy rings around a moon for first time
Artist's impression of Rhea's rings
Friday, 07, Mar 2008 02:32
Scientists believe they may have spotted rings around Saturn's moon Rhea, the first time such material has been seen orbiting a moon.
Nasa says a broad debris disk and at least one ring were detected by instruments onboard the Cassini spacecraft.
It was previously thought that only planets in our solar system had rings.
A report on Rhea's rings, published in the journal Science, says the apparent debris disk measures several thousand miles from end to end.
It is thought the particles probably range in size from small pebbles to boulders.
An additional dust cloud may also extend up to 3,000 miles from the moon's centre.
Scientific calculations show that it is possible for Rhea to maintain rings.
"Like finding planets around other stars, and moons around asteroids, these findings are opening a new field of rings around moons," said Norbert Krupp, a scientist on Cassini's magnetospheric imaging instrument from the Max Planck Institute for Solar System Research.
The rings may be remnants from an asteroid or comet collision in Rhea's distant past.
"The diversity in our solar system never fails to amaze us," said Candy Hansen, Cassini scientist at Nasa's Jet Propulsion Laboratory.
"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."