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Great Red Spot

The Great Red Spot is a perpetual anticyclonic (high-pressure) storm on the planet Jupiter, 22° south of the equator. It rotates counterclockwise with a period of about 6 days and is large enough to be clearly visible in telescopic images from Earth.

The Great Red Spot is approximately 14,000 kilometers across in the north-south direction and varies from 24,000 to 40,000 kilometers across in the east-west direction; three entire Earths could fit within its boundaries. The cloud tops within the Great Red Spot are approximately 8 kilometers above the surrounding cloud tops.

It is not known exactly what causes the Great Red Spot's reddish color; one theory is that phosphorus compounds raised from deeper in the atmosphere by the Spot's updrafts are responsible, but this remains speculative. The Great Red Spot is remarkably stable, having first been spotted by Galileo Galilei over 300 years ago. Several factors may be responsible for its longevity, such as the fact that it never encounters solid surfaces over which to dissipate its energy and that its motion is driven by Jupiter's internal heat. Simulations suggest that the Spot tends to absorb smaller atmospheric disturbances.

At the time of writing, the Great Red Spot is approximately half as large as it was 100 years ago. It is not known how long the Great Red Spot will last, or whether this is a result of normal fluctuations.

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This dramatic view of Jupiter's Great Red Spot and its surroundings was obtained by Voyager 1 on February 25, 1979, when the spacecraft was 5.7 million miles (9.2 million kilometers) from Jupiter. Cloud details as small as 100 miles (160 kilometers) across can be seen here. The colorful, wavy cloud pattern to the left of the Red Spot is a region of extraordinarily complex and variable wave motion. To give a sense of Jupiter's scale, the white oval storm directly below the Great Red Spot is approximately the same diameter as Earth.

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