1. Chemical Sources and Sinks of OCS in the Lower Atmosphere of Venus Yuk L. Yung M. C. Liang, California Institute of Technology yly@gps.caltech.edu EGU Meeting 2008

2. Important Processes in the Atmosphere of Venus Catalytic Chemical Cycles Heterogeneous Chemistry Middle Atmosphere Circulation OCS as tracers of chemistry and dynamics

3. Venus model description Two-dimensional Caltech/JPL KINETICS chemical transport model Solve continuity equation for 24 species with ~200 chemical reactions (subset of Mills’)

4. Role of circulation Affect the upward flux of OCS from the surface Reduce OCS abundances at high latitudes

8. S2S2 OCS S3S3 S4S4 S8S8 hv S S CO S4S4 S2S2 S S3S3 S4S4 hvS

11. Conclusions Scale height of OCS cannot be explained by photolysis alone Photosensitized dissociation of OCS via polysulfur photochemistry Integrated destruction rate of OCS is 23,000 Tg- S/yr [Earth = 10 Tg-S/yr]

12. Acknowledgements NASA and ESA P. Drossart R. L. Shia K. Baines D. Crisp C. Lee X. Jiang B. Bezard E. Marq

13. Not Used