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.