Pressure-induced absorption by H2 in the atmosphere of Jupiter and Saturn |
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| Authors: | Terry Z Martin Dale P Cruikshank Carl B Pilcher William M Sinton |
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| Institution: | Institute for Astronomy, University of Hawaii, Honolulu, Hawaii, 96822, USA |
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| Abstract: | The S(1) line of the pressure-induced fundamental band of H2 was identified and measured in the spectra of Saturn and Jupiter. This broad line at 4750 cm?1 lies in a region free from telluric and planetary absorptions. It is about 99% absorbing in the core; the high-frequency wing extends to at least 5100 cm?1. We compare the obseved line shape to the predictions of both a reflecting-layer model (RLM) and a homogeneous scattering model (HSM). The RLM provides a good fit to the Saturn line profile for temperatures near 150K; the derived base-level density is 0.52 (+0.26, ?0.17) amagat and the H2 abundance is 25 (+10, ?9) km-amagat, assuming a scale height of 48 km. The Jupiter line profile is fit by both the RLM and HSM, but for widely differing temperatures, neither of which seems probable. The precise fitting of the observed S(1) line profile to computed models depends critically on the determination of the true continuum level; difficulties encountered in finding the continuum, especially for Jupiter, are discussed. Derived RLM densities and abundances for both planets are substantially lower than those derived from RLM analyses of the H2 quadrupole lines, the 3ν3 band of CH4, and from other sources. |
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