The Load Love Numbers for Various Rheological Models of Venus

Abstract

The load Love numbers for different rheological models of Venus are calculated, based on a static approach for the surface load (the planetary relief) and buried anomalous density waves. The planet was modeled as an elastic self-gravitating body with radius-dependent density, compression modulus, and shear modulus. The calculations have been performed for each harmonic up to the degree and order n = 70, based on the accuracy of determining the gravity field at the moment. This article considers three rheological models of Venus. A purely elastic model (model A) was analyzed first. In the second case (model B) we assume the presence of an elastic lithosphere, under which a weakened layer extending to the core was introduced, which partially lost its elastic properties. The weakening in this layer was modeled by a ten times lower shear modulus. The thickness of the elastic lithospheric layer varied from 100 to 500 km. In the third model (model C), a gradient change in the shear modulus was set in the weakened layer under the crust, that is, a ten times decrease in the shear modulus directly under the crust gradually increased to its value in the elastic model at the core boundary. On the basis of the described models, the interpretation of the anomalous external gravitational field has been carried out. It is shown that the load numbers are sensitive to the rheological structure of the planet and this can be used when choosing between the rheological models of Venus. A relief map of the crust–mantle boundary was constructed, as calculated under the assumption of isostatic compensation. The obtained values of the crust thickness may be slightly less than the real ones, since the component of dynamic compensation was not taken into account in the work.