35.10-P

Magellan Radio Occultation Studies of Venus' Atmosphere (1991-1994)

J.M. Jenkins (SETI Inst.), D.P. Hinson (Stanford Univ.)

We have been conducting a systematic study of the middle and lower atmosphere of Venus through analysis of 20 radio occultation experiments conducted with the Magellan spacecraft between October, 1991, and August, 1994. These studies have revealed a rich but sparsely sampled trove of information regarding the structure, composition and dynamics of the Venus atmosphere. The five sets of experiments sampled a variety of latitudes in both hemispheres from below to , and were conducted on as little as 2 to as many as 5 consecutive orbits on each date. Basic results include vertical profiles of: (i) electron density in the ionosphere, (ii) pressure, temperature, density, and static stability in the neutral atmosphere (from 33 km to 98 km), and (iii) sulfuric acid vapor ( ) abundance below the main cloud deck (Jenkins et al., Icarus 110, 79-94, 1994). Further analysis of the temperature profiles led to the discovery of small vertical-scale gravity waves in the neutral atmosphere (Hinson and Jenkins, Icarus 114, 310-327, 1995). The retrieved profiles show intriguing zonal variations that might be due to planetary-scale waves. New results obtained in the past year include profiles of meridional wind speed at several latitudes. This paper will focus on presenting results from the 1994 occultations, and on comparing the results from all experiments to study latitudinal and meridional variations.

This work was supported under NASA Planetary Atmospheres Program Grants NAGW-4346, NAGW-4341, and NAG5-4321.