This false-color picture of a thunderstorm near Jupiter’s Great Red Spot was taken by the Galileo spacecraft in June, 1996. “Near” on Jupiter means about 10,000 km. The white cloud in the center is a tall, thick cloud 1,000 km across, extending 25 km or so higher than most of the surrounding clouds. The cloud base extends off to the left and appears red in this picture.
Different wavelengths of light penetrates to different depths in Jupiter’s atmosphere before being reflected back by clouds. Red represents data taken with the 756 nm filter, a wavelength where Jupiter’s atmosphere allows the light to penetrate deeply. Green and blue represent data taken with the 727 and 889 nm filters where the gases in the atmosphere absorb strongly, so only high clouds can reflect the light. The green and blue areas show high clouds; the red areas show deep clouds.
This red color indicates that the cloud base is very deep in the atmosphere, about 50 kilometers below the surrounding clouds. Most of the features in Jupiter’s clouds are ammonia clouds at a pressure just less than Earth’s sea level pressure. On Jupiter, water is the only substance forming clouds deeper in the atmosphere where the pressure is about five times the Earth’s sea level pressure. The red base of this thunderstorm is so deep that it can only be a water cloud. In 1979, the Voyager spacecraft detected convective clouds of this type near the Great Red Spot, but their cameras could not allow the determination of the storms’ altitude.
It is thought that these storms are analogous to an Earth thunderstorm, with the cloud’s high, bright, white portion comparable to the anvil clouds we see on Earth. We can’t tell it the precipitation is rain or snow, but there are indications that storms on Jupiter have lightning in them. The greatest difference between this storm and thunderstorms on Earth is the scale. The anvil of this storm is 1,000 km across and 75 km high. Here on Earth, the largest anvils are 200 km across and 18 km high. The image covers an area approximately 9,000 by 7,000 km. The thumbnail on the left shows an area of similar size on the Earth.
Image Credits: NASA