Great Dark Spot
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The Great Dark Spot was a dark spot on Neptune similar to Jupiter's Great Red Spot. Although it looked nearly the same as Jupiter's spot, it was not thought to be a storm but instead an atmospheric hole similar to the hole in Earth's ozone layer.
The spot was detected by NASA's Voyager 2 probe, which passed Neptune in 1989. It was comparable in size to Jupiter's spot, and was located in the southern hemisphere. Winds measured in the spot were up to 1,500 miles an hour (2400 km/h) (the highest of any planet). The spot appeared to change as the spacecraft flew by, and does so in many pictures of it. The spot was believed to have been rotating counterclockwise. Over the Great Dark Spot were concentrated regions of crystal methane and frozen water particle clouds that resemble cirrus clouds on Earth.
When the Hubble Space Telescope viewed Neptune again in June 1994, the spot had vanished. However, another spot very much like the old one appeared in the planet's northern hemisphere later that year. [1] It is unknown why the Great Dark Spot appeared nor is it known whether it is a common occurrence or a rarer phenomenon. Neptune is blue due to the large amounts of methane gas in its atmosphere. Its atmosphere is mainly hydrogen and helium. Some scientists think the movement of the Great Dark Spot is because of the 2250 km/h (1400 mph) jet stream winds on Neptune.
[edit] References
- The Great Dark Spot. Welcome to the Planets. Planetary Data Systems (NASA).fr:Grande tache sombre
