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The Question

(Submitted April 20, 1997)

How long will the Great Red Spot on Jupiter last?

The Answer

The Great Red Spot on the face of Jupiter has been in place since the early 1600's when telescopes were first used to observe surface features on the Sun, Moon and planets, thus is it very stable. The dynamics of the Jovian atmosphere, and all turbulent systems, are quite complicated, and no one can say for sure how long a structure such as the Great Red Spot will last. However, it has been a very active area of fluid dynamics research lately. The spot is what is known as a "coherent vortex structure". It has undergone only minor variations in size and color. The vortex is a type of cyclone in Jupiter's upper atmosphere, and the wind speeds within it can be up to 360 km/hour. The clouds are rotating counter-clockwise in the southern hemisphere, indicating it is an area of of high pressure with respect to the clouds around it. The vortex is maintained by forcing from the opposite shearing motion from the cloud bands on the sides of the vortex and from the very fast rotation of Jupiter, once every 9.6 hours. For more details on the dynamics of the Great Red Spot, see http://www.jpl.nasa.gov/galileo/ganymede/092396.html. The short answer to your question is that it is not known how long the spot will persist.

Neptune also has large spots on its surface, but they are not as long-lived as Jupiter's Great Red Spot. You can read about how one such spot on Neptune was seen to fade at http://www.arcadiastreet.com/cgvistas/neptune_006.htm.

Regards,

Padi Boyd
for the "Ask an Astrophysicist" Team

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