36th DPS Meeting, 8-12 November 2004
Session 18 Outer Planets
Poster I, Tuesday, November 9, 2004, 4:00-7:00pm, Exhibition Hall 1A

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[18.10] Vertical Discrimination in the Zonal Wind Speeds of Jupiter and Saturn

T. Tavenner, N. Chanover, J. Murphy, J. Norwood (NMSU), L.C. Roberts (AMOS-The Boeing Company)

Jupiter and Saturn were imaged using the AO-Vis camera on the AEOS 3.63-meter telescope on Haleakala throughout 2002 and the first half of 2003. The data were taken with tip/tilt correction, enhancing the spatial resolution, and using a pair of filters designed to probe different altitudes in the giant planet atmospheres. One filter is centered on a methane absorption band at 727 nm, while the other is centered on a nearby continuum region at 751 nm. In the absence of clouds, the filters would span an order of magnitude in pressure sensitivity. With the presence of the uppermost cloud deck, assumed to be composed of ammonia based on chemical equilibrium arguments, the two filters effectively sound to the center and upper boundary of the tropospheric cloud deck. Such a pair of filters provides vertical discrimination in the giant planet atmospheres, allowing for the search for variations in the cloud levels and the horizontal ("zonal") winds with height.

We present wind speeds for several different latitudes and known cloud features on Jupiter and Saturn, and discuss the variation of these winds with altitude. While Jupiter's zonal wind jets are thought to be relatively stable, recent reports of a decrease in Saturn's zonal winds at cloud level near the equator suggest that differences between the two planets exist. The stability of the zonal wind jets has important implications for the modeling of global circulation and energy balance in the giant planet atmospheres. We compare our results with those derived from recent remote sensing observations of the giant planets by the Hubble Space Telescope and the Galileo and Cassini spacecraft. This comparison serves to illustrate the respective advantages of orbiting spacecraft versus long-term ground-based telescopic observations with enhanced spatial resolution.

This work was supported by the National Science Foundation through the NSF/AFOSR Astronomy Program: NSF/AST-0335665, NSF/AFT-0123471.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.