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A.J. Friedson, E. Wilson (JPL/Caltech), J.I. Moses (LPI)
Extrasolar giant planets (EGPs) orbiting close to stars with a well-developed chromosphere receive very high fluxes of stellar far-ultraviolet radiation due to their proximity to the primary. The intense UV irradiation will break down water and methane in the upper atmosphere to initiate chemistry involving oxygen-bearing radicals (primarily OH and O), simple and complex hydrocarbons, and mixed organics such as carbon dioxide, HCO, formaldehyde, and methanol. We are currently engaged in exploring the implications of photochemistry for the carbon budget. Preliminary results indicate that photochemistry tends to drive carbon into carbon monoxide in the upper atmospheres of these planets at temperatures and pressures where thermochemical equilibrium would dictate that methane should be the dominant carbon-bearing molecule. The results of the modeling has important implications for understanding how photochemistry might alter the initial carbon budget of an EGP during the course of its evolution and inward migration toward its parent star as well as for the formation of photochemical hazes that might significantly affect the emergent spectra of these objects.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.