HR: 1340h
AN: P53A-1455    [Abstracts]
TI: Titan solar reflection and emission properties in the EUV/FUV
AU: * Liu, X
EM: xianming@usc.edu
AF: X. Liu, University of Southern California, Los Angeles, CA 90089 United States
AU: Shemansky, D E
EM: dons@hippolyta.usc.edu
AF: X. Liu, University of Southern California, Los Angeles, CA 90089 United States
AU: Yung, Y
EM: yly@gps.caltech.edu
AF: D. Shemansky, University of Southern California, Los Angeles, CA 90089 United States
AU: Team, C U
EM: candice.j.hansen
AF: Y. Yung, California Institute of Technology, Pasadena, CA 91125 United States
AB: \noindent Cassini UVIS imaging spectrograph exposures of Titan in the first fly-by show the resolved absorption structure of acetylene (C$_{2}$H$_{2}$ ) and ethylene (C$_{2}$H$_{4}$) in the 130 -- 190 nm region of the solar reflection spectrum. A simple model of the reflection and extinction process indicates the underlying scattering layer is consistent with a constant albedo in the 130 - 180 nm region and a relatively sharp rise between 180 - 190 nm. In reality the reflection is a more complex interplay between gaseous absorption and aerosol scattering. Molecular absorption by CH$_{4}$, C$_{2}$H$_{2}$, and C$_{2}$H$_{4}$ dominate in the 130 - 170 nm region. As the gaseous absorptions becomes weaker beyond 170 nm, the albedo increases. At 190 nm it is more than a factor of three higher than that at 130 nm. The brightening is tentatively attributed to aerosols formed from the condensation of heavy hydrocarbons. The spatially averaged spectrum contains abundances of 4. $\times$ 10$^{16}$ cm$^{-2}$ and 2.2 $\times$ 10$^{16}$ cm$^{-2}$ in C$_{2}$H$_{2}$, and C$_{2}$H$_{4}$ respectively. Atmospheric emission is also present, showing a distinctive spectrum containing N$_{2}$ bands, atomic nitrogen, atomic carbon, and possibly CH emission features. The atomic nitrogen emission lines indicate that most of the population is in the $^{2}$D state, inferring that the emission is at a high enough altitude that quenching by electrons and other species are not effective against the 17 hour emission lifetime of the state. A preliminary analysis will be presented.
UR: http://lasp.colorado.edu/cassini
DE: 5704 Atmospheres--composition and chemistry
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting