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[12.10] Hydrocarbon Distribution in Saturn's Upper Atmosphere. Re-analysis of Saturn's Voyager UVS H-Lyman-alpha and He 584 A Airglow

L. Ben-Jaffel (Institut d'Astrophysique de Paris-CNRS, Paris, France), D. Feng (Institute of Atmospheric Physics, Univ. of Arizona), F. Herbert (Lunar and Planetary Laboratory, Univ. of Arizona)

Simultaneous re-analysis of respectively the Voyager 2 UVS stellar Occultation observations obtained during the spacecraft encounter with Saturn and an IUE albedo spectrum of the planet obtained in 1983, provided the height distributions of eleven minor constituents from the top of the troposphere up to the atmospheric homopause region. These constituents are: CH₄, C₂H₂, C₂H₄, C₄H₂, C₂H₆, H₂O, GeH₄, PH₃, AsH₃, CO₂, and NH₃. A thin layer of H₂O is discovered near altitude 625 km. Our results seem to be consistent with HC abundances recently derived from ISO observations (Feng et al., 2000). We use the derived HC distribution to model the H Lyman-alpha and He 584 A airglow of Saturn observed by Voyager UVS in 1982, with a focus on the helium abundance in the upper atmosphere.