Possible Chemical Composition And Interior Structure Models Of Venus Inferred From Numerical Modelling

Abstract

Venus’ mass and radius are similar to those of Earth. However, dissimilarities in atmospheric properties, geophysical activity, and magnetic field generation could hint toward significant differences in the chemical composition and interior evolution of the two planets. Although various explanations for the differences between Venus and Earth have been proposed, the currently available data are insufficient to discriminate among the different solutions. Here we investigate the possible range of models for Venus’ structure. We assume that core segregation happened as a single-stage event. The mantle composition is inferred from the core composition using a prescription for metal-silicate partitioning. We consider three different cases for the composition of Venus defined via the bulk Si and Mg content, and the core’s S content. Permissible ranges for the core size, mantle, and core composition as well as the normalized moment of inertia (MoI) are presented for these compositions. A solid inner core could exist for all compositions. We estimate that Venus’ MoI is 0.317–0.351 and its core size 2930–4350 km for all assumed compositions. Higher MoI values correspond to more oxidizing conditions during core segregation. A determination of the abundance of FeO in Venus’ mantle by future missions could further constrain its composition and internal structure. This can reveal important information on Venus’ formation and evolution, and, possibly, the reasons for the differences between Venus and our home planet.