Word: planet
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Dates: during 1980-1989
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...Uranian moons and sent back incredibly detailed photographs of the five larger, previously known satellites. It had photographed the nine known rings and found at least two more. The versatile spacecraft also managed to pry a bewildering volume of information from Uranus itself, despite the fact that the giant planet is shrouded by a thick and opaque blue-green atmosphere...
Scientists at J.P.L. seemed most fascinated by Voyager's close-up views of the five major Uranian moons. By far the most exotic was Miranda, about 300 miles across and the closest of the large moons to the planet. Miranda, Geologist Laurence Soderblom explained, "is a bizarre hybrid," combining at least ten different types of terrain, some similar to the "valleys and layered deposits of Mars . . . the grooved terrain of Ganymede (a moon of Jupiter) and the depression faults of Mercury." The crusts of Miranda and three of the four other major moons, Soderblom said, "have been tectonically shuffled...
...Voyager swung behind Uranus, it bounced radio waves off the rings and discovered that they are quite different from those of Saturn, which contain an abundance of fine particles. The Uranian rings are made largely of dark "boulders," most of them more than a yard wide, that circle the planet once every eight hours. Many scientists believe they may be the remnants of a large moon that shattered in an ancient cataclysm...
...fact, some astronomers have long suspected that it was a catastrophic event, perhaps a collision with an earth-size object, that toppled Uranus on its side (see chart); it spins with its rotational axis practically perpendicular to those of most of the other planets. The spacecraft raised even more questions about Uranus when it discovered that the planet has a magnetic field about as strong as earth's but topsy-turvy by terrestrial standards, with the north magnetic pole displaced by 55 degrees from the south geographic pole. The odd arrangement led scientists to speculate that Voyager had caught...
...magnetic field also helped scientists calculate the length of a Uranian day. By detecting the changing radio emissions caused by the interaction of the field with the solar wind as the planet turns on its axis, the spacecraft established that Uranus rotates once approximately every 17 hours. The technique, explained Physicist James Warwick, can be likened to standing on a lawn and "feeling the water drops every time a sprinkler goes around." By tracking clouds in the atmosphere, Voyager discovered high-altitude winds moving around the planet at 220 m.p.h., more than twice as fast as they travel above...