DPS 2001 meeting, November 2001
Session 7. Outer Planet Atmospheres I: Dynamics and Clouds
Oral, Chairs: A. Showman, P. Yanamandra-Fisher, Tuesday, November 27, 2001, 3:50-5:00pm, Regency E

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[7.02] Jovian Tropospheric Cloud Structure from Galileo/NIMS 5 micron Observations

M. Roos-Serote (Lisbon Astr. Obs.), S.K. Atreya (Univ. of Michigan), M. Wong (GSFC), P. Irwin (Univ. of Oxford), P. Drossart (Obs. Paris-Meudon)

It is now well-established from both in situ measurements (Galileo Probe) and infrared remote sensing (Voyager/IRIS, ISO/SWS, Galileo/NIMS) that hot spots, which cover a small percentage of the Jupiter's disk mainly close to the equator, are areas with greatly depleted abundance of the condensable volatiles water, hydrogen sulfide (as ammonium sulfide) and ammonia, and little cloud cover. In particular, no detectable cloud opacity is present between 2 and 10 bar in these areas. Based on a hypothesis for the origin of Jupiter's atmosphere, the global elemental oxygen abundance (derived from water vapor) on Jupiter must be at least solar, and perhaps even supersolar in view of a factor of 2-3 enrichment of other heavy elements, C,N,S,Ar,Kr and Xe (Owen et al. 1999 Nature 402 p.269; Atreya et al. 1999, PSS 47,p.1243). Recently, it was possible to identify a Galileo Near Infrared Mapping Spectrometer (NIMS) observation of a hot spot and its close surroundings, that had also been observed by the Solid State Imager camera on Galileo, some 64 hours earlier (Gierasch et al. 2000 Nature 403, p.628; Ingersoll et al. 2000 Nature 403, p.630) A localised storm system seen in the visible image, could be related to significant amounts of water vapor retrieved from the NIMS spectra of the same region (Roos-Serote et al. 2000 Nature 406, p.158), suggesting the presence of a large water cloud. A systematic study was undertaken on selected NIMS 5 micron spectra, outside the hot spot areas in the North Equatorial Belt, to attempt a determination of the oxygen abundance and the corresponding cloud structure that is compatible with the infrared spectrometry measurements in the 5 micron window. We find that for these non hot spot spectra, a significant water cloud can exist at pressures greater than approximately 5 bar, which would imply an oxygen elemental ratio (to H) greater greater than 1 - 2 times solar.

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