National Geographic : 1980 Jan
15° 12° 90° 60 +o ,o UPITER, UNROLLED in two views taken four months apartby Voyagers 1 and 2 and aligned by longitude (left), shows changes in the bright zones and dark belts of the planet's atmosphere. Most evident are the 30-degreewestward migration of the GreatRed Spot in the southern hemisphere and the changed posi tions of the white ovals beneath it. Numberedarrows show velocities and directions of clouds, including those in the turbulent Great Red Spot re gion (lower left). 30° Near the equator, a row of white horsetailclouds, somewhat dissipat ed after four months, releases heat from below by convection. Their regu lar spacing, as with the small white ovals, may be caused by waves in the rapidly rotatingplanet'satmosphere. Jupiter's atmosphere may have flow patterns more predictable than those of earth's, but its chemistry is more complex. Depending on tem perature and pressure,cloud decks of different chemicalcomposition,inter layered with transparent hydrogen and helium gas (diagram)form a sandwich a hundred kilometers thick. Whereas earth has only one zone of weather, the troposphere, based on the evaporation, condensation, and precipitation of water, Jupiter has VisioN three: one of water, one of ammonium hydrosulfide, and one of ammonia. Below the atmosphere, the planet is mainly liquidhydrogen andhelium. It has no solid surface. AJupiter movie Scientists studying movements in the atmosphere of Jupiter employ time-lapse still photographyconvert ed to a movie. To approximate that effect, hold the magazine closed and flip the lower right-hand comer back to front with your left thumb so that the small images of the planet appear to show motion.