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The No. 1989 Great Dark Spot (also known as GDS-89[1]) was a dark spot on Neptune similar in appearance to Jupiter's Great Red Spot. It was discovered in 1989 by NASA's Voyager 2 probe. Although it appears similar to Jupiter's spot, which is an anticyclonic storm (this is like a hurricane), it is believed that the Great Dark Spot is an atmospheric hole similar to the hole in Earth's ozone layer.
However, the insides of Great Dark Spots are mostly cloud-free, and unlike Jupiter's spot, which has lasted for hundreds of years, their lifetimes appear to be much shorter, forming and disappearing once every few years or so. Based on pictures taken by Voyager and since then with the Hubble Space Telescope, Neptune appears to spend a little bit more than half its time with a Great Dark Spot.
- ↑ Hammel, H. B.; Lockwood, G. W.; Mills, J. R.; Barnet, C. D. (1995). "Hubble Space Telescope Imaging of Neptune's Cloud Structure in 1994". Science. 268 (5218): 1740–1742. Bibcode:1995Sci...268.1740H. doi:10.1126/science.268.5218.1740. PMID 17834994. S2CID 11688794.