Jupiter's atmosphere defies predictions


  • Michael Carlowicz


A month late in coming, the weather report is finally in from Jupiter, and the skies seem to be hotter, windier, drier, and clearer—but much less electric—than most forecasters predicted. In fact, the preliminary data gathered from the Galileo probe may lead planetary scientists to rethink not just the meteorology of the gaseous planet, but its very origins. The preliminary results were presented on January 22 from NASA's Ames Research Center.

According to measurements made by the probe's atmospheric structure instrument and interpreted by Alvin Sieff, a principal investigator from San Jose State University, the temperature at Jupiter ranged from −144°C at the top of the ammonia-cloud covered atmosphere to +152°C at 600 km into it. Pressures ranged from 400 millibars to 22 bars over the same descent path, compressing the gases in some places to densities 100 times greater than previously postulated. The extremes of temperature and pressure created a vertical convective motion in the atmosphere, stirring up turbulent east- to-west (or prograde) winds reaching 531 km/hr, more than 50% stronger than most predictions.