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[31.09] Hydrocarbon Chemistry in the Atmospheres of Six Extrasolar Giant Planets

C. S. Boxe, Y. L. Yung (Caltech), M. A. Allen, R. A. West (JPL), J. I. Moses (LPI)

Using Saturn as a proxy, the photochemistry in the atmospheres of six extrasolar giant planets, illuminated by the central stars HD 20630, HD 087696, HD 189689, HD 165475, HD 5132, and HD 124428, is investigated using Moses et al's (2000) one-dimensional diurnally-averaged chemical model for Saturn. We report distinct variations in the mixing ratios of CH₄, C₂H₆, C₂H₂, C₂H₄, and CH₃ as a function of pressure. The mixing ratios for the principal hydrocarbon species at 10^-3 mbar varies by orders of magnitude as a function of the total energy flux in the UV region (0 to 2000 Angstroms) from the central star.