36th DPS Meeting, 8-12 November 2004
Session 30 Jupiter and Saturn: Composition, Structure, Dynamics
Oral, Thursday, November 11, 2004, 1:45-4:15pm, Clark

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[30.10] Latitudinal Variations of Saturn's Near-Infrared Spectrum

N. J. Chanover (New Mexico State Univ.), G. Bjoraker (NASA/GSFC), T. Hewagama (U. Maryland)

Near-infrared spectra of Saturn were acquired at the NASA Infrared Telescope Facility using SpeX on 06-09 January 2002 and 12-13 February 2004. Using the long wavelength cross-dispersed mode, spectra between 2.7-5.5 microns were recorded simultaneously at a spectral resolution R ~ 2000. With the slit of the spectrograph aligned parallel to Saturn's rotation axis, spectra were extracted for different latitude bands on Saturn to enable a comparison of the trace species mixing ratios as a function of latitude. Synthetic infrared spectra were generated for comparison with the observational data using the Synthetic Spectrum Program, which was developed at NASA/GSFC. We performed sensitivity studies to determine which of Saturn's spectral line(s) in the 5 micron region would be suitable diagnostics of local dynamics. We varied the mixing ratio of ammonia between 100--400 parts per million (ppm) to determine which spectral features are sensitive to such variations. As is also true for Jupiter, the NH3 line at 1957 cm-1 was most sensitive to changes in Saturn's NH3 mixing ratio. The phosphine mixing ratio was varied between 1--4 ppm; the PH3 line at 1972 cm-1 proved to be most sensitive to these variations. Thus, these lines provide leverage to determine mixing ratio gradients, provided there are no clouds in the line formation region.

We compare observed and modeled spectra in an effort to characterize any spatial variations in Saturn's trace constituents, which could be indicative of localized or regional dynamical processes. We vary the mixing ratios of ammonia and phosphine, as well as the pressure level boundaries of the absorbing region. Our exploration of this parameter space will be discussed.

This work was supported by NASA under grants NAG5-7904 and NNG04GA51G.

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