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J.D. Goguen, R.T. Clancy, M.J. Wolff (SSI), P.B. James (U. Toledo)
We model HST STIS spectra of Mars taken on 18 August 2001 (Ls=216\circ) to retrieve the albedo, w, and asymmetry parameter, g, of the dust particles over the 220-305 nm wavelength range. The figure summarizes the combinations of w, g and \tau (dust) that fit STIS spectra near the disk center and places our UV results in the context of the Pathfinder dust model (Tomasko et al., 1999). Our nominal case is \tau=2.0, w=0.64, and g=0.84. We use Mie theory to calculate the change in w and g for the Tomasko et al. dust size distribution (a=1.6\mum, b=0.2) with wavelength shortward of 443.6 nm. The change in w and g from 443.6 to 260 nm requires that ni increase to 0.020 (from 0.0122). Future work will use MGS-TES IR dust opacity measurements to better constrain \tau.
This work was supported in part by a grant from the STScI.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.