GEOLOGICAL CORRELATIONS WITH THE INTERIOR DENSITY STRUCTURE OF VENUS

A model has been constructed by stipulating that Venusian long-wavelength topography and geoid elevations are explained by the sum of density anomalies associated with mantle convection and lithospheric compensation mechanisms. For convenience the latter are represented by a single Airy surface because individual lithospheric components cannot be resolved at the wavelengths considered in this paper. Mantle convection is represented at a single depth by mass perturbations that drive viscous flow. We invert spherical harmonic representations of the topography and the geoid to create global representations of the mantle convection pattern and near-surface density anomalies. The mantle convection pattern matches well with previous numerical simulations of mantle convection that show a pattern of isolated upwellings amidst an interconnected network of downwellings. The near-surface density anomalies show no particular pattern. The inversion results have been compared with a global synthesis of Magellan data. Impact crater density does not correlate with the mantle convection pattern or the near-surface density anomalies. Large volcanic structures are associated with upwellings. Planitiae are associated with downwellings. Coronae are anticorrelated with high-amplitude upwellings and downwellings and apparently are passive features associated with rifting that is related to mantle convection in a complex fashion. Tesserae are associated with negative lithospheric density anomalies interpreted as areas of thickened crust. Tesserae show no definitive relationship to the present mantle convection pattern.