Post SL9 Impact Model of Jupiter's Albedo Below 200nm Wavelength

I. Dashevsky, J. Caldwell (York University), L.M. Trafton (U. Texas), S.K. Atreya, S. Edgington (U. Michigan), K.S. Noll (STScI), H.A. Weaver (JHU)

Using a planetary atmospheres doubling and adding code, we have modelled Hubble Space Telescope data from the aftermath of the impacts of periodic comet Shoemaker-Levy 9 on Jupiter. We concentrated on the region below 200 nm to investigate transient trace constituents in the post-impact atmosphere. We use FOS data from July 18 longward of 180 nm and GHRS data from July 21 shortward of 180 nm to produce a hybrid spectrum for study. It is necessary to pay careful attention to dark counts (GHRS) and grating scatter(FOS) because the post-impact Jupiter signal is very low at wavelengths below 200 nm. When the previously reported effects of gas phase CS2, NH3 and C2H2 (Yelle and McGrath, Edgington et al.) are accounted for, the model albedo below 180 nm is higher than the observed one. We cannot reduce the differences using plausible continuum scattering parameters, including a Henyey-Greenstein phase function, aerosol/haze scattering, particle optical depth, mean radius, distribution, and refractive index. We note that approximately 0.001 cm-am of gaseous H2O at the top of the Jovian atmosphere may account for the difference.