The Internal Evolution of Vesta

Abstract

Within the general framework of differentiation in the early solar system, the asteroid Vesta is a particularly interesting case study. First, its size is well constrained, simplifying modeling efforts that can concentrate on bodies of relevant size. Second, the rich diversity of HED meteorites provides constraints on bulk composition and a unique opportunity to confront predictions of numerical models with petrologic reality. Finally, the Dawn mission, in addition to confirming the link between Vesta and the HED’s, also provides critical constraints on the internal density structure and composition of the asteroid. In this chapter we begin by considering petrologic and geochemical constraints on the bulk composition and differentiation time-scales of Vesta, before presenting modeling efforts to understand its chemical and physical evolution. The modeling indicates accretion within the first million years of solar system history and complex thermal and chemical retroactions linked to the redistribution of 26Al during transport of melt toward the surface. Formation of a shallow magma ocean is predicted, leading to a vertically stratified mineralogical structure with olivine sequestered at depth and protracted cooling at depth. These features are consistent with the essential features of HED petrology and chronology and observations of the Dawn mission.