DEEP WINDS ON JUPITER AS MEASURED BY THE GALILEO PROBE

The Doppler Wind Experiment on the Galileo probe provided the first in situ data on wind speeds in Jupiter's atmosphere. Initial analysis(1) of the results indicated that wind speeds increase with depth, rather than decaying to zero below the cloud tops or remaining relatively co nstant as had previously been assumed(2). But this earlier analysis wa s subject to several potential sources of error, as highlighted by the fact that wind speeds measured at the cloud tops did not seem to matc h those inferred from tracking clouds(3) in images obtained by the Voy ager spacecraft, Here we report new analyses of the probe data that us e a corrected treatment of the timing errors, adopt the measured(4) (r ather than predicted) descent trajectory, and incorporate a new calibr ation of the instrumentation that takes into account the unexpectedly high temperatures encountered by the probe. We determine wind speeds a t the cloud tops (700-mbar level) in the range 80-100 m s(-1), in agre ement with the results of cloud tracking; the speed increases dramatic ally between 1 and 4 bar, and then remains nearly constant at similar to 170 m s(-1) down to the 21-bar level. The increase in wind speed im plies a latitudinal density gradient of 0.5% per degree in the 1-2 bar altitude range, but whether these winds are driven by internal heat o r absorbed sunlight remains uncertain.