Ammonia ice cloud on Jupiter. This colorized composite infrared image was taken by NASA's Galileo spacecraft on June 26, 1996. Ammonia ice (light blue) is shown in clouds northwest of the Great Red Spot. This cloud was produced by updraft of ammonia-laden air from deep within Jupiter's atmosphere. The Great Red Spot has existed for at least 300 years and is the oldest and largest weather system in our solar system. It measures over 20,000 kilometers wide (over 12,400 miles), and has twice the width of the Earth.