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[37.03] An explanation of the SO2 profile on Venus from the Vega 1 and 2 UV spectrometers

B. Fegley, L. Schaefer (Planetary Chemistry Laboratory, Washington University)

We use chemical equilibrium calculations to model the SO2 gradient from the UV spectrometers on Vega 1 and 2. They found SO2 decreases from ~125 ppmv to ~25 ppmv with decreasing altitude. We can match the gradient by varying the oxygen elemental abundance with altitude. Variations range from +47 (cloud base) to -186 ppm (near surface) of the total oxygen elemental abundance. Figure 1 compares our results to the reported SO2 profile. We reproduce many features of gas chemistry in Venus' lower atmosphere including: (1) increases in SO3 and H2SO4 near the cloud base, (2) decreases in H2O upward from the cloud base, (3) decreases in OCS above ~22 km, and (4) increases in OCS below ~22 km. However CO increases towards Venus' surface.

Supported by NASA NAG5-11037.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.