Latitudinal Variations of Sulfur Compounds in the Venus Atmosphere Based on the Correlation Between VLA Observations and Radio Occultation Results
M.A. Kolodner, S.H. Suleiman (Georgia Inst. of Tech.), B.J. Butler (NRAO), P.G. Steffes (Georgia Inst. of Tech.)
To identify the presence of potential spatial variations in the
distributions of sulfur compounds (H 
SO 
(g) and SO ) across
the disk of Venus, a dual-frequency radio observation was performed
with the NRAO/VLA at 14.94 GHz (2 cm) and 22.46 GHz (1.3 cm) on April
5, 1996. The resulting brightness maps have been compared with a
radiative transfer model, which shows both equatorial and polar limb
darkening beyond that due to a simple CO /N atmosphere. Our
radiative tranfer model shows that the measured darkening results
directly from the microwave opacity of SO and H SO (g).
Specifically, in the equatorial regions, it has been found that the
limb darkening corresponds to that expected from an H SO (g)
abundance profile such as that derived from the equatorial Mariner 10
radio occultation experiment, and from a nominal subcloud SO
abundance of 75 ppm. In the polar regions, the increased limb
darkening is consistent with the more broad vertical distribution
of gaseous H SO such as that derived from Magellan radio
occultation experiments in high latitude regions. The magnitude of
the polar limb darkening also requires a corresponding elevation
in the sub-cloud SO abundance to 150 ppm or more.
This work was supported by the NASA Planetary Atmospheres Program under grants NAG5-4190 and NAGW-533.