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Published February 24, 2009 | Published
Journal Article Open

Modeling the distribution of H_2O and HDO in the upper atmosphere of Venus


The chemical and dynamical processes in the upper atmosphere of Venus are poorly known. Recently obtained vertical profiles of trace species from the Venus Express mission, such as HCl, H_2O, and HDO, provide new information to constrain these processes. Here, we simulate these profiles, using the model we have developed and described in a related paper by Yung et al. (2008), with special emphasis on the modeling of H_2O and HDO. A new mechanism, the photo-induced isotopic fractionation effect (PHIFE) of H_2O and HCl, is incorporated into our model. The observed enhancement of HDO could be attributed to (1) preferential destruction of H_2O relative to HDO via PHIFE and (2) escape of hydrogen that enhances the abundance of D and hence its parent molecule HDO. Over a wide range of the sensitivity of the results to the changes of the two mechanisms, we find that the observed profiles of HDO and H2O profiles cannot be explained satisfactorily by current knowledge of chemical and dynamical processes in this region of the atmosphere. Several conjectures to tackle the problems are discussed.

Additional Information

© 2009 American Geophysical Union. Received 31 January 2008; accepted 2 December 2008; published 24 February 2009. Special thanks are due to J.-L. Bertaux for providing H_2O, HDO, HCl, and HF profiles from Venus Express. We thank H. Hartman, N. Heavens. K. F. Li, V. Natraj, C. Parkinson, R. L. Shia, and X. Zhang for critical comments. This research was supported in part by NSC grant 97-2628-M-001-001 to Academia Sinica and NASA grant NNX07AI63G to the California Institute of Technology.

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Published - Liang2009p55510.10292008JE003095.pdf


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