The reason the ring didn't show up in Cassini's photographs is because the particles are too big to reflect like mist when backlit by the sun and too small for direct imagery. "We think it is mostly rubble, about 1 centimeter in size," Hansen-Kohascheck said. "If you were standing on Rhea, you probably could see it." The disk measures several thousand miles from end to end. An additional dust cloud may extend up to 3,000 miles, or 5,900 kilometers, from the center of the moon. Scientists believe the ring may be remnants of an asteroid or comet that crashed into the moon eons ago. The smash-up would have left a cloud of gas and solid particles around Rhea. When the gas dissipated, the particles remained. Scientists ran dozens of computer simulations to verify that Rhea, Saturn's second-largest moon after Titan, could hang on to a ring, considering the physics of its size and location, without the particles migrating away. The moon is about 950 miles (1,500 km) in diameter. The discovery has scientists wondering if other moons in the solar system might have rings too. "It's worth taking a look," said Hansen-Kohascheck. "We haven't seen hints of rings around the others, but we weren't looking for them either." Related Links: |
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