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[10.11] The correlation of zonal bands and zonal winds in HST/STIS images of Jupiter and Saturn

M.B. Vincent (NMSU), J.T. Clarke (U. of Mich.), J.T. Trauger (JPL)

Jupiter and Saturn were imaged with the HST/STIS FUV MAMA (115 to 119 nm). This bandpass is sensitve to Rayleigh scattering and acetylene photoabsorption. The effective pressures for Jupiter and Saturn are about 30 and 60 mbar, respectively.

We examine the correlation between the zonal bands seen in the STIS images and the zonal winds at the cloud tops. Regions of upwellings on Jupiter, the visible zones, generally appear brighter in the STIS images than downwellings at the visible belts. This correlation between brightness and vertical winds is opposite that seen in WFPC2 F160W images. The difference in appearance could be explained if the upwellings are enriched in ammonia and aerosols, which darken the F160W bandpass, and depleted in acetylene, which darken the STIS bandpass.

Saturn's equatorial upwelling is slightly brighter than the adjacent latitudes of downwelling. Other bands seen on Saturn have boundaries at prograde jets, and can straddle latitudes of upwellings and downwellings. In October 1997, Saturn's northern hemisphere is brighter than the southern hemisphere. The dark polar hoods on both planets have boundaries at high-latitude prograde jets.

This research has been supported by grant GO-8171.01-97A from the Space Telescope Science Institute to the University of Michigan.