On Earth, storms can last a few days. The Great Red Spot on Jupiter is a storm that has been going on for more than 400 years now. What is different on Jupiter that makes it possible for storms to last so long?
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4$\begingroup$ Size, relative "smoothness" of surface compared with radius, $\endgroup$– Carl WitthoftOct 9, 2020 at 13:06
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6$\begingroup$ It is not sure that the spot first seen in the 17th century is the same as today, as there is a large gap in observations. It is at least 150 years old though, which is already quite long for a storm, at least from our point of view. nasa.gov/feature/goddard/… $\endgroup$– Jean-Marie PrivalOct 9, 2020 at 15:10
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1$\begingroup$ Laboratory simulation of Jupiter's great red spot by rotating shallow water $\endgroup$– Robert HarveyOct 9, 2020 at 22:01
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$\begingroup$ Laboratory simulation of Jupiter's Great Red Spot $\endgroup$– Robert HarveyOct 9, 2020 at 22:04
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2$\begingroup$ And here: “Think of the GRS [Great Red Spot] as a spinning wheel that keeps on spinning because it’s caught between two conveyor belts that are moving in opposite directions. The GRS is stable and long-lived, because it’s ‘wedged’ between two jet streams that are moving in opposite directions." $\endgroup$– Robert HarveyOct 9, 2020 at 22:11
1 Answer
Standard answers, as found here, (partial quote)
Unlike Jupiter, the Earth has land masses that cause major storms to lose energy due to friction with a solid surface. Without this feature, Jupiter’s storms are more long-lasting. However, the Great Red Spot is long-lived, even by Jupiter standards. Researchers don’t quite understand why, but we do know that Jupiter’s storms that are located in cloud bands with the same direction of rotation tend to be longer lasting.
So, we know some of the probable reasons, and don't know the full story yet. Keep in mind that the current RedSpot might be a 3-sigma event, even for Jupiter.