DPS Meeting, Madison, October 1998
Session 32P. Jupiter II
Contributed Poster Session, Wednesday, October 14, 1998, 5:10-6:10pm, Hall of Ideas

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[32P.11] Comparing Voyager, Galileo and ISO 5 micron spectra of Jupiter: new constraints on the vertical tropospheric cloud structure in hot spot regions.

M. Roos-Serote (Observatorio Astronomico de Lisboa, Portugal), P. Drossart, Th. Encrenaz (Observatoire de Paris-Meudon, France), R. W. Carlson, F. Leader (Jet Propulsion Laboratory, USA)

Voyager/IRIS spectra of Jupiter have been intensively analyzed over the past 2 decades. In particular, from the 5 micron window, all of the analyses (hot spot regions) concluded on a 3 layer vertical cloud structure: an ammonia cloud at 0.5 bar, an ammonium--hydrosulfide cloud at 2 bar and a water cloud somewhere between 4 and 7 bar.

However, the Galileo Entry Probe entered a hot spot region, and did not detect any cloud features between 1.6 and 22 bar, where it ceased functioning. Galileo/NIMS and ISO/SWS 5 micron spectra agree with the Probe findings in that cloud opacity below the 2 bar level in the model atmosphere results in a poor fit to these data.

When comparing the shapes of the IRIS spectra to those of the NIMS and ISO spectra, a slope in the IRIS spectra is found for wavelengths shorter than 5 micron, not present in the NIMS and ISO spectra. As a consequence of this slope, in order to fit the IRIS data, an additional opacity is needed somewhere between 3 and 8 bar in the model atmosphere, that has been interpretated as the presence of a water cloud. We suggest that either a calibration problem with IRIS for wavelengths shorter than 5 micron, or temporal variations in the deep atmosphere of Jupiter are the cause.

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