Is C2H2 Present Deep in the Jovian Atmosphere?
Y. B\'{e}tr\'{e}mieux, R. V. Yelle (Center for Space Physics, Boston University) On Jupiter, acetylene (C2H2) is widely accepted to be produced predominantly by methane photolysis by UV photons and hence should be found high in its stratosphere. Moreover, observations indicate that the C2H2 abundance decreases rapidly with increasing pressure throughout the stratosphere. However, spectroscopic observations conducted by HST’s Faint Object Spectrograph (FOS) suggest that C2H2 is present in significant abundance in the upper troposphere. The FOS spectra exhibit C2H2 features shortward of 190.0~nm that are consistent with C2H2 located in the upper stratosphere above 50~mbar. Also detected are pronounced C2H2 features overlapping with ammonia (NH3) features longward of 200.0~nm. Using a radiative transfer model that incorporates Raman scattering by molecular hydrogen reveals that these features can only be explained with a C2H2 mixing ratio of 1~\times~10-7 or more below the 150~mbar level.
