These four images track the largest and most intense storm observed by Cassini. The two lower images were taken 11 hours apart—the length of one day on Saturn. Each composite image combines 84 different shots taken on February 26, 2011. The two top images—the storm's head (left) and middle (right)—are enlargements from the image below them, as indicated by the white subset lines. The storm's head was moving at 63 miles an hour.
Altogether, the storm covers an area approximately eight times the surface area of the Earth and encircles Saturn's entire 186,000-mile circumference.
The storm clouds are likely water covered by crystallized ammonia, and they are traveling 60 miles above the normal, non-storm clouds. The false colors represent the altitudes of the various cloud layers—blue being the highest and red being the lowest. Lightning occurs in the lowest layer of the atmosphere.