What is the Great Dark Spot? The Great Dark Spot was a huge spinning storm in the southern atmosphere of Neptune which was about the size of the entire Earth. Winds in this storm were measured at speeds of up to 1,500 miles per hour. These were the strongest winds ever recorded on any planet in the solar system! The Great Dark Spot was first discovered when the Voyager 2 spacecraft flew by Neptune in 1989. When the Hubble Space Telescope looked at Neptune in 1994, the Great Dark Spot was gone and a different dark spot had appeared in the northern atmosphere of Neptune.