The Solar System

Gas Giants

What is Neptune’s atmosphere like?

Despite its distance from the Sun, conditions on Neptune are remarkably active and energetic, which is not what you might expect from a bitterly frigid environment. Neptune is subject to some of the fiercest winds in the solar system, up to 700 miles (1,100 kilometers) per hour. Its layer of blue surface clouds whips around with the wind, while an upper layer of wispy white clouds—probably composed of methane crystals—rotates with the planet. A darker cloud layer, probably composed of hydrogen sulfide, lies below the methane. The Voyager 2 flyby of Neptune showed three notable storm systems on the planet: the Great Dark Spot, which is about the size of Earth; the Small Dark Spot, about the size of our Moon; and a small, fast-moving, whitish storm called “Scooter” that seems to chase the other storms around the planet. In 1994, however, observations by the Hubble Space Telescope showed that 144 the Great Dark Spot had disappeared.


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