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[30.04] Photochemical Modeling of the Distribution of C3H8 in the Atmosphere of Saturn

S. G. Edgington (JPL/CalTech), A. Simon-Miller, D. Jennings, G. Bjoraker, P. Romani, R. Achterberg (NASA/GSFC), G. Orton (JPL/CalTech), M. Flasar (NASA/GSFC), Cassini CIRS Team

Cassini's Composite Infrared Spectrometer (CIRS) has measured the abundance of C₂H₂ and C₃H₈ (Propane) at several latitudes in the Southern hemisphere. An increase of radiance with latitude towards the pole has been observed, possibly implying a corresponding increase of C₃H₈.

In an effort explain the observed distribution of both species, it is important to model the creation, destruction, and transport of these chemical species. Furthermore, since both molecules have overlapping absorption features in the same spectral region near 748 cm^-1, such modeling will aid in refining derived abundances and separating temperature effects. The photochemistry model used in Edgington et al. (1998, 1999, 2000) to model simultaneously hydrocarbons, ammonia, and phosphine is updated and expanded to include paths relevant to the creation of C₃H₈. Destruction occurs through photolysis, while transport would tend to spread C₃H₈ from its source regions.

With a series of exercises in 1- and 2- dimensions, we explore the extent to which photolysis, vertical, and/or meridional transport impacts the distribution of C₂H₂ and C₃H₈ with latitude. Thermal profiles derived from CIRS observations versus latitude are used as they have an impact on numerous reaction rates. We then compare these results with abundances derived from observations taken with the CIRS instrument.

Edgington, S.G., West, R.A., Friedson, A.J., Atreya, S.K., 2000. A 2-D photochemical model with meridional circulation. Bull. American. Astron. Soc., 32, 1013.

Edgington, S.G., S.K. Atreya, L.M. Trafton, J.J. Caldwell, R.F. Beebe, A.A. Simon, and R.A. West, 1999. Ammonia and eddy mixing variations in the southern hemisphere of Jupiter from HST Faint Object Spectrograph Observations. Icarus, 142, 342-357.

Edgington, S.G., S.K. Atreya, L.M. Trafton, J.J. Caldwell, R.F. Beebe, A.A. Simon, R.A. West, and C. Barnet, 1998. On the latitude variation of ammonia, acetylene, and phosphine altitude profiles on Jupiter from HST Faint Object Spectrograph Observations. Icarus, 133, 192-209.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.