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National Geographic : 1990 Aug
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ago we competed with the Soviet space program. Now three Soviet scientists sit as official members on the Voyager science teams. Otherwise, the aura of chronic astonishment persists. Every day brings at least one discovery. Now only 3.5 million kilometers from Neptune, Voyager has already discovered four small moons. It has been tracking not just the Great Dark Spot but also a small dark spot called D2 and a fast-moving white spot nicknamed the Scooter. Early images of Triton look mottled. Are we seeing the sur face? Or is it an obscuring haze? The surprise of the day, however, is a faint new ring. Unlike the brighter arcs, this ring completely encircles the planet. Ring specialists are beginning to suspect that the arcs may simply be parts of a complete ring. The invisible sections would contain too few particles to reflect much light. But what causes the ring particles to clump into arcs? At Saturn, scientists saw that rings were shepherded by small nearby moons whose gravity confined the rings. At Neptune, Voyager can find no confining moonlets. Could it be that the ring arcs formed quite recently? In the past few years could a comet have crashed into a small moon, creating debris that has not yet had time to organize into a smooth ring? Although the scientists propose this idea, few like it. Imaging team leader Brad Smith expresses their skepticism: "That violates something called the cosmological principle, which says that it is unlikely that you happen to be at the right place at the right time to observe an event of cosmic significance." Imaging Neptune's rings is a challenge. The ring particles are darker than charcoal. The spacecraft is moving fast enough to cross the U. S. in less than four minutes. There is about as much light out there as inside a cathedral on a cloudy day. "It's a photographer's nightmare," says one imaging expert. Voyager's seasoned engineers have worked miracles. In order to steady the HEIDIHAMMEL(TOP, RIGHT);JAMESA. SUGAR, BLACKSTAR (ABOVE) A good view ofNeptune from Earth (top, at right), a near-infrared image, contrasts with an image recorded at the same time by Voyager from 1.5 million kilometers. International cooperation marked the Neptune encounter: Soviet scientists worked with NASA at the Jet Propulsion Laboratory in Pasadena, California. National Geographic,August 1990
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