The Depths of Saturn Revealed: Discrete Cloud Systems and Winds at the 2-Bar Level as Imaged by Cassini/VIMS

HR: 15:25h
AN: P23D-08 [Abstracts]
TI: The Depths of Saturn Revealed: Discrete Cloud Systems and Winds at the 2-Bar Level as Imaged by Cassini/VIMS
AU: * Baines, K H
EM: blueskies4321@yahoo.com
AF: Jet Propulsion Laboratory/ CalTech, M/S 183-601, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Drossart, P
P23D-08 AF: Observatoire de Paris, CNRS-UMR 8362, DESPA, Meudon, 92195 France
AU: Roos-Serote, M
P23D-08 AF: Observatorio Astronomico de Lisboa, Tapada da Ajuda, Lisbon, 1349-018 Portugal
AU: Formisano, V
P23D-08 AF: Istituto di Fisica dello Spazio Interplanetario, Area Ricera Tor Vergata, Rome, 00198 Italy
AU: Momary, T
EM: momary@mail1.jpl.nasa.gov
AF: Jet Propulsion Laboratory/ CalTech, M/S 183-601, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Brown, R H
P23D-08 AF: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 United States
AU: Bellucci, G
P23D-08 AF: Institut d'Astrophysique Spatiale, Universite de Paris, Orsay Campus, Paris, 91405 France
AU: Bibring, J
P23D-08 AF: Observatoire de Paris, CNRS-UMR 8362, DESPA, Meudon, 92195 France
AU: Bibring, J
P23D-08 AF: Institut d'Astrophysique Spatiale, Universite de Paris, Orsay Campus, Paris, 91405 France
AU: Buratti, B J
P23D-08 AF: Jet Propulsion Laboratory/ CalTech, M/S 183-601, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Capaccioni, F
P23D-08 AF: ) Istituto di Astrofisica Spaziale, Area Ricerca Tor Vergatia, Rome, 00198 Italy
AU: Cerroni, P
P23D-08 AF: ) Istituto di Astrofisica Spaziale, Area Ricerca Tor Vergatia, Rome, 00198 Italy
AU: Clark, R N
P23D-08 AF: ) U.S. Geological Survey, MS 964, Box 25046, Federal Center, Denver, CO 80225 United States
AU: Combes, M
P23D-08 AF: Observatoire de Paris, CNRS-UMR 8362, DESPA, Meudon, 92195 France
AU: Coradini, A
P23D-08 AF: ) Istituto di Astrofisica Spaziale, Area Ricerca Tor Vergatia, Rome, 00198 Italy
AU: Cruikshank, D
P23D-08 AF: ) U.S. Geological Survey, MS 964, Box 25046, Federal Center, Denver, CO 80225 United States
AU: Cruikshank, D
P23D-08 AF: NASA/Ames Research Center, MS 245-6, Moffett Field, Palo Alto, CA 94035 United States
AU: Jaumann, R
P23D-08 AF: Institute for Planetary Exploration, DLR, Rutherfordstrasse 2, Berlin, 12489 Germany
AU: Langevin, Y
P23D-08 AF: Institut d'Astrophysique Spatiale, Universite de Paris, Orsay Campus, Paris, 91405 France
AU: Matson, D
EM: dennis.matson@jpl.nasa.gov
AF: Jet Propulsion Laboratory/ CalTech, M/S 183-601, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: McCord, T
P23D-08 AF: Space Science Institute NW, N/A, Winthrop, WA 98765 United States
AU: Mennella, V
P23D-08 AF: Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, Naples, 80131 Italy
AU: Nelson, R M
EM: reobert.m.nelson@jpl.nasa.gov
AF: Jet Propulsion Laboratory/ CalTech, M/S 183-601, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Nicholson, P D
P23D-08 AF: Cornell University, Space Sciences Building, Ithaca, NY 14853 United States
AU: Sicardy, B
P23D-08 AF: Observatoire de Paris, CNRS-UMR 8362, DESPA, Meudon, 92195 France
AU: Sotin, C
P23D-08 AF: Laboratoire de Planetologie et Geodynamique, University de Nantes 2 rue de Houssiniere, BP92208, Nantes, 44322 France
AB: We present imagery and analysis of discrete, deep-level systems of clouds as revealed near the 2-bar level in 5.1-micron thermal-infrared images obtained by the Visual Infrared Mapping Spectrometer onboard the Cassini/Huygens orbiter. At this wavelength, the clouds are seen silhouetted against the indigenous thermal radiation upwelling from depth. The thermal flux dominates reflected sunlight, so that the clouds and their movements can be readily observed on both the day and night sides of the planet. During four Saturn passes from February to July, 2005, high-spatial-resolution images were obtained at spatial scales from 225 to 750 km per VIMS pixel, revealing a variety of intriguing deep cloud features over a large range of spatial scales. Axisymmetric structures are significantly more heterogeneous and narrower in latitudinal breadth than observed at higher altitudes. Various shapes and wave-like structures are observed in the largest features with longitudinal dimensions exceeding 3000 km, including circular and oval features, donut-shaped structures, and swirls. Center-to-limb spectral analysis of several features as observed on both the day and night sides at diagnostic hydrogen and methane-absorbing wavelengths places these 5-micron-discrete clouds near the 2-bar level. Tracking such thermally-backlit clouds enables the determination of winds at near the two-bar level near where relatively large particles (> ~5 micron radius) reside within a major cloud layer, possibly composed of ammonium hydrosulfide or water condensates, but not ammonia. Comparison of these winds with those determined by tracking sunlit cloudtops residing near the 1-bar-level enables the estimation of vertical windshears. Specifically, direct comparison with contemporary cloudtop wind measurements by Cassini/ISS (Porco et al., 2005, Science 307, 1243-1247) indicates a strong wind shear exists at depth in the Equatorial Region, with winds increasing with depth from the stratosphere above the 100-mbar level downward to at least the 2-bar level. At the equator, when compared to 1-bar-level results of Porco et al. (2005), we find a tropospheric windshear of ~ 1.8 m/(s-km) in the 1-2-bar region, close to the 1.5 m/(s-km) value observed in the 1-2 bar region of Jupiter by the Galileo probe (Atkinson et al., 1998, JGR 103, 22,911-22,928). Outside the Equatorial Region, shears are significantly less.
DE: 5700 PLANETARY SCIENCES: FLUID PLANETS
DE: 5704 Atmospheres (0343, 1060)
DE: 5739 Meteorology (3346)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005