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[11.16] Deuterium Abundance from HD and CH₃D Reservoirs in the Atmosphere of Jupiter

C. D. Parkinson, L. Ben Jaffel (Institut d'Astrophysique de Paris-CNRS, France), J. C. McConnell (Dept. of Earth and Atmospheric Science, York U., Canada)

CH₃D is an isotopic tracer in the deep Jovian atmosphere and susceptible to transport and chemical effects. It is expected that the tropospheric ([D]/[H])_{CH_4} ratio determined from the various observations made should be relatively invariable, yet previous determinations of this quantity for Jupiter have given results inconsistent with experimental error bars. This suggests that there may be a problem with the interpretion of some of the observations, or that the apparent CH₃D column abundance is variable. We report on the effects of varying important parameters over this pressure regime on the CH₃D mixing ratio, CH₃D fractionation, the ([D]/[H])_{CH_4} and D/H (= ([D]/[H])_{H_2}) ratios and compare with the various CH₃D and HD observations.

Our results show that since the CH₃D mixing ratio is strongly dependent upon K(z) in the region of interest where temporal or latitudinal variations in K(z) could significantly impact the measured ([D]/[H])_{CH_4} ratio. The K(z) adopted represents complex upward convection and downdraft mixing that occurs in the Jovian atmosphere as evidenced by recent observations (Gierasch et al. (2000); Ingersoll et al., 2000; Roos-Serote et al., 2000; Vincent et al., 2000). Using our technique allows for the first time a way to explain the discrepancies in the ([D]/[H])_{CH_4} ratio observations by offering a plausible link between the CH₃D observations and upper tropospheric dynamical processes.

In any case our calculations show how ([D]/[H])_{CH_4} can be used as a diagnostic tracer to constrain K(z) and better understand the dynamics of the atmosphere in this pressure regime.

References:

Gierasch, P.J., Ingersoll, A. P., Banfield, D., Ewald, S. P., Helfenstein, P., Simon-Miller, A., Vasavada, A., Breneman, H. H., Senske, D. A., and the Galileo Imaging Team, Observations of moist convection in Jupiter's atmosphere, Nature, 403, 628--630, 2000.

Ingersoll, A. P., Gierasch, P.J., Banfield, D., Vasavada, A., and the Galileo Imaging Team, Moist convection as an energy source for the large-scale motions in Jupiter's atmosphere, Nature, 403, 630--632, 2000.

Roos-Serote, M., Vasavada, A. R., Camp, L., Drossart, P., Irwin, P., Nixon, C., Carlson, R. W., Proximate humid and dry regions in Jupiter's atmosphere indicate complex local meteorology, Nature, 405, 158--160, 2000.

Vincent, M. B., et al., Mapping Jupiter's Latitudinal Bands and Great Red Spot Using HST/WFPC2 Far-Ultraviolet Imaging, Icarus, 143, 189--204, 2000.

The author(s) of this abstract have provided an email address for comments about the abstract: parkinso@iap.fr

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