The Great Red Spot in Jupiter's southern hemisphere as imaged by NASA's Galileo spacecraft in June 1996. The Great Red Spot is a gigantic, oval-shaped vortex some five miles above the surrounding cloud deck. Its dimensions are approximately 12,500 miles in the east-west direction by 7,500 miles in the north-south direction.

The Great Red Spot is a high-pressure system in which warm gases from below are forced upward. After they reach the top level, they spread, cool, and sink back to lower elevations. The circulation of the Great Red Spot that we see is in the counterclockwise direction and due to the Coriolis force.

Note, Jupiter rotates in the same direction as Earth, namely from west to east. The Great Red Spot lies in Jupiter's southern hemisphere. Large-scale low-pressure systems in the southern hemisphere rotate in the clockwise direction (see terrestrial hurricane example, on previous page); large-scale high-pressure systems rotate in the counterclockwise direction.