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发帖数: 1994 | 1 Two Hours Before Neptune
Credit: Voyager 2, NASA
Explanation: Two hours before closest approach to Neptune in 1989, the Voyager 2 robot
spacecraft snapped this picture. Clearly visible for the first time were long light-colored
cirrus-type clouds floating high in Neptune's atmosphere. Shadows of these clouds can even
be seen on lower cloud decks. Most of Neptune's atmosphere is made of hydrogen and
helium, which is invisible. Neptune's blue color therefore comes from smalle |
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