Jupiter changes its appearance from image to image, as the camera of the European Space Agency's Infrared Space Observatory (ISO) examines the giant planet with a succession of filter settings. Each selects a different infrared wavelength, which carries unique information about the chemistry and weather in Jupiter's atmosphere. The wavelengths are measured in microns (thousandths of a millimetre).
At 3.0 microns the striped planet appears broadly similar to views by visible light, in which bright zones of clouds ringing Jupiter alternate with darker belts. Most Luminous at this wavelength is the zone around the equator. The bright blob below the equator is Jupiter's Great Red Spot, created by a storm that has lasted for centuries.
At 3.3 microns Jupiter disappears! The blackout results from strong absorption of infrared rays of this wavelength by methane gas in the atmosphere. The surrounding speckles have no meaning. Even the blackness of this image demonstrates ISO ability to analyse the planet's chemistry.
At 5.7 microns, regions of strong emissions in a northern belt appear as hot -spots in this strange-looking image of Jupiter. They are dry, anti-cyclonic regions of sinking gas, where ISO is able to peer deep into the atmosphere. The hot-spot emissions are strongest at 5.0 microns.
At 7.6 microns ISO is looking at the stratosphere, high in Jupiter's atmosphere . Notice the brightness of the south polar region, at the bottom of the image.
At 9.4 microns, cloudy zones that were bright in the image above are relatively dark, while the intervening belts now outshine them. The Great Red Spot is also seen towards the bottom of the image.
The position of the Great Red Spot shifts slightly to the right, from the first to the last image in the selection. Jupiter rotated noticeably on its axis during the 35 minutes that ISOCAM spent examining the planet.
A complete set of 86 images, each at a different wavelength, has been made available to broadcasters as a video animation with the release of the ISO/ESA Information Note;
"ISO celebrates its prolonged life with a video of Jupiter".
Credit: ESA/ISO, ISOCAM & Th. Encrenaz et al.