WIND-RELATED FEATURES AND PROCESSES ON VENUS - SUMMARY OF MAGELLAN RESULTS

A search of Magellan synthetic aperture radar images covering similar to 98% of the venusian surface shows that aeolian features occur at al l longitudes and latitudes. A global data base for wind streaks, the m ost common type of aeolian feature, was developed. For each of the 597 0 streaks in the data base, information was compiled on location, stre ak type, radar backscatter, dimensions, azimuth, orientation with resp ect to local slope, and type of landform with which it is associated. In addition, streaks occurring in association with parabolic ejecta de posits were designated type P streaks, which constitute about 31% of t he data base. Wind streak azimuths were analyzed to assess wind patter ns at the time of their formation. Both hemispheres show strong westwa rd and equatorward trends in azimuths, consistent with Hadley circulat ion and inferred upper atmospheric westward zonal winds. When type P s treaks (those considered to result from transient impact events) were removed, the westward component was greatly reduced, suggesting that t he upper zonal winds do not extend to the surface. The presence of equ ator-oriented streaks at high latitudes suggests that Hadley circulati on extends to the poles. A field of possible yardangs found southwest of Mead Crater strikes NE-SW and occupies plains situated in a shallow topographic depression. Analysis of non-type P streaks in the area su ggests that equatorward winds are funneled through the depression and are responsible for the erosion of the terrain to form the yardangs. D une deposits are limited on Venus. Two dune fields were identified (Ag lonice and Fortuna-Meshkenet) which total in area about 18,300 km(2). Microdunes are proposed for some southern hemisphere areas which show distinctive radar reflectivities. Bragg scattering and/or subpixel ref lections from the leeward faces of microdune bedforms could account fo r the unusual radar backscatter cross sections. (C) 1995 Academic Pres s, Inc.