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Monday, September 14, 1998 Mystery revealedScientists: Jupiter's rings are dustPASADENA, Calif. (AP) -- Why, it's just space dust. The faint rings around Jupiter come from clouds of dust that are the result of cosmic debris battering Jupiter's small moons, according to data from the Galileo spacecraft. The rings -- which are nearly invisible to even the best telescopes -- clearly show their relation to the orbits of four small inner moons, scientists said Tuesday. "Pictures are the smoking gun that allow us to say this theory works," said Joseph Burns, the Cornell University astronomy professor who arrived at the explanation for the rings. It was long thought that the only ringed planet was Saturn, with its prominent, icy bands, but the Voyager spacecraft revealed in 1979 that Jupiter also was surrounded by rings. A more detailed look by the unmanned Galileo revealed the rings are more numerous and complex than thought. Michael Belton, an astronomer with the National Optical Astronomy Observatories in Tucson, Ariz., joined Burns and Cornell colleagues Joseph Veverka and Maureen Ockert-Bell to release the findings and images during a media teleconference from Cornell. Dust grains and particles of comets and asteroids drawn by Jupiter's strong gravity stream toward its irregularly shaped moons at about 25 miles a second -- 100 times the speed of a bullet, Veverka said. They slam into the moons, creating explosive dust clouds that eventually turned into orbiting rings so tenuous that the stars shine right through them. Because of Galileo, "we now have a definitive answer to the origin of this ring system and we now understand the processes which lead to their appearance," said Belton, leader of the Galileo imaging team. "It's a big step forward." Galileo, launched in 1989, arrived at Jupiter in December 1995 and began a two-year tour of Jupiter and its four largest moons. The current two-year mission extension is focusing on the moon Europa. The material was jointly announced with the Jet Propulsion Laboratory in Pasadena, which manages the Galileo project.
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