Parallel bands of clouds have long been seen in Earth-based observations of Jupiter, and the reddish area below the equator, the Great Red Spot, has been known to exist for more than 300 years. Spacecraft images from the Pioneer and Voyager missions have revealed details in the atmosphere that cannot be seen from Earth.
Pioneer: First Mission To Jupiter
On March 2, 1972, Pioneer 10 was launched from the John F. Kennedy Space center to become the first spacecraft to venture into the outer solar system. Eleven months later, the spacecraft had successfully passed through the asteroid belt, and on December 3, 1973, came within 130,000 kilometers (80,800 miles) of the cloud tops of Jupiter.
Both Pioneer 10 and Pioneer 11, which encountered Jupiter a year later, had 11 scientific instruments and experiments designed to map magnetic fields and radiation in interplanetary space, and determine the atmospheric structure of Jupiter and Saturn. An additional magnetometer was added to Pioneer 11 to study high-strength magnetic fields.
Discovered by Voyager 1 in 1979, a faint ring of particles surrounds Jupiter with an outer edge 128,000 kilometers (80,000 miles) from the center of the planet. This image of the ring was taken by Voyager 2 on July 10, 1979, and shows the sharp outer boundary and more diffuse inner ring which may extend to the cloud tops of Jupiter.
The Atmosphere of Jupiter
The Jovian atmosphere contains numerous belts and storm systems with wind speeds up to 400 kilometers/hr. (250 miles/hour). Between the dark and light cloud zones, wind shear and turbulence create great rotating storm systems, best exemplified by the Great Red Spot.
The Great Red Spot
With an area almost equal to the entire surface area of the Earth, the Great Red Spot is a hurricane-like feature that rises some 8 kilometers (5 miles) above the surrounding clouds. At this height the atmosphere is cool enough so that phosphorus may condense, creating the red color.