The debris disc NASA’s Cassini spacecraft has found evidence of material orbiting Rhea, Saturn’s second largest moon. This is the first time rings may have been found around a moon. Saturn’s second-largest moon Rhea, pictured by the Cassini probe on March 29, 2012. Credit: NASA/JPL. "Whatever is going on there is a real puzzle, so ultimately there may be another explanation, but from what we have at the moment a debris disc and embedded rings are the best explanation," Jones told New Scientist. The discovery was a result of a Cassini close fly-by of Rhea in November 2005, when instruments on the spacecraft observed the environment around the moon. The particles that make up the disk and any embedded rings probably range from the size of small pebbles to boulders. This view of the Saturn-facing hemisphere of Rhea (1,528 kilometers, or 949 miles across) allows a glimpse of the wispy terrain that covers the trailing hemisphere of Rhea. Normally, narrow rings require a small moon to shepherd the particles and keep them confined, but no satellites of Rhea have been spotted so far. Sleek Rings, Rugged Moon Rhea floats below the innermost regions of Saturn's amazing rings. The models show that Rhea’s gravity field, in combination with its orbit around Saturn, could allow rings that form to remain in place for a very long time. An additional dust cloud may extend up to 5,900 km from the moon's centre, almost eight times the radius of Rhea. Rings are not just for planets anymore – astronomers have found them around Saturn’s moon Rhea, the first ever observed around a moon. Saturn’s Moon Rhea Also May Have Rings. March 6, 2008 Source: NASA. Saturn's Moon Rhea Also May Have Rings PASADENA, Calif. - NASA's Cassini spacecraft has found evidence of material orbiting Rhea, Saturn's second largest moon. This is the first time rings may have been found around a moon. Rhea may also have a tenuous ring system, which … Rhea, a moon of Saturn which is just 1500 km across, appears to be surrounded by a debris disc and possibly rings, just like its parent planet.