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The exploration of Neptune has only begun with one spacecraft, ''Voyager 2'', which visited on August 25, 1989. Currently there are no approved future missions to visit the Neptunian system. NASA, ESA and also independent academic groups have proposed future scientific missions to visit Neptune. Some mission plans are still active, while others have been abandoned or put on hold. ==''Voyager 2''== (詳細はEarth. ''Voyager 2'' studied Neptune's atmosphere, Neptune's rings, its magnetosphere, and Neptune's moons. Several discoveries were made, including the discovery of the Great Dark Spot and Triton's geysers. ''Voyager 2'' revealed that Neptune's atmosphere is very dynamic, even though it receives only 3% of the sunlight that Jupiter receives. ''Voyager 2'' discovered an anticyclone called the Great Dark Spot, similar to Jupiter's Great Red Spot. However, images taken by the Hubble Space Telescope revealed that the Great Dark Spot had disappeared. Also seen in Neptune's atmosphere at that time was an almond-shaped spot designated D2, and a bright, quickly moving cloud high above the cloud decks, dubbed "Scooter". ''Voyager 2'' found four rings and evidence for ring arcs, or incomplete rings, above Neptune. Neptune's magnetosphere was also studied by ''Voyager 2''. The planetary radio astronomy instrument found that Neptune's day lasts 16 hours and 7 minutes. ''Voyager 2'' also discovered auroras, like those on Earth, but much more complex. ''Voyager 2'' discovered six moons orbiting Neptune, but only three were photographed in detail: Proteus, Nereid, and Triton. Proteus turned out to be an ellipsoid, as large as an ellipsoid could become without rounding into a sphere. Proteus is very dark in color, almost like soot. Nereid, though discovered in 1949, still has very little known about it. The probe flew past Triton about away, and was the last solid world ''Voyager 2'' explored within the Solar System. Triton was revealed to have remarkable active geysers and polar caps. A very thin atmosphere was found, as well as thin clouds. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Exploration of Neptune」の詳細全文を読む スポンサード リンク
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