This is an image of Neptune's Great Dark Spot of 1989.
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Neptune's Great Dark Spot of 1989
Unlike Jupiter's Great Red Spot, the Great Dark Spot of Neptune is thought to be a hole in the methane cloud deck of Neptune. The white clouds shown in the picture are above the "hole". In many images of Neptune, the Great Dark Spot can be seen to change size and shape.
The Great Red Spot of Jupiter is thought to be a hurricane which has been raging on Jupiter for at least 400 years. The Great Dark Spot, seen here by Voyager in 1989, disappeared in 1994, and was replaced very soon by a similar "Spot" in a similar place, but in the northern hemisphere instead of in the southern hemisphere.
The Great Dark Spot of 1989 either dissipated or is currently masked by other aspects of Neptune's atmosphere. Whatever the reason, its disappearance demonstrates that Neptune has a dynamic, rapidly changing atmosphere.
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