Global Variations in the Geoid/Topography Admittance of Venus
Global representations of geoid height and topography are used to map variations in the geoid/topography ratio (admittance) of Venus. The admittance values are permissive of two mutually exclusive models for convection-driven topography. In the first, compressive highland plateaus are expressions of present mantle downwelling, broad volcanic rises are expressions of mantle upwelling, and lowlands overlie regions with no substantial vertical motion in the mantle. In the second, compressive highland plateaus are remnants of an earlier regime of high crustal strain, and most other long-wavelength topographic variations arise from normal convective tractions at the base of the lithosphere.
© 1994 American Association for the Advancement of Science. We thank D. T. Sandwell for discussions that led to the original idea for the admittance maps, A. S. Konopliv and W. L. Sjogren for making available the most recent Venus geoid solutions, N. J. Rappaport for her solution for harmonic topography, and R. J. O'Connell, G. Masters, and S. Evans for helpful computer code. Figures 1-3 in this paper were generated with the Generic Mapping Tools system [P. Wessel and W. H. F. Smith, Eos72, 441 (1991)]. This work was sponsored by NASA under grants NAGW-3276 and NAGW- 3425 and by the Magellan Project under contract JPL 957070 from the Jet Propulsion Laboratory.