The primordial collisional history of Vesta: crater saturation, surface evolution and survival of the basaltic crust

Abstract

This work explores the implications of the Jovian Early Bombardment (JEB) for the evolution of the primordial Vesta, in particular in terms of crater saturation, crustal excavation and surface erosion. Both scenarios assuming the planetesimals having formed in a quiescent or a turbulent nebula were explored and both primordial and collisionally evolved size-frequency distributions were considered. The results obtained indicate that, if the basaltic surface of Vesta were already formed, the JEB would saturate it with craters and could erode it to depths that vary from hundreds of meters to tens of kilometres. In the latter cases, the surface erosion caused by the JEB would be comparable with the thickness of the eucritic and diogenitic layers of Vesta. In the cases where the global surface erosion is limited, however, large impactors, if too abundant, can excavate the whole crust and extract significant quantities of material from the vestan mantle, incompatible with the present understanding of HED meteorites. This appears to be the case if the impacting planetesimals formed in a turbulent nebula and Jupiter migrated by 0.5 AU or more. Globally, the results obtained suggest that the scenarios where the planetesimal formed in a quiescent nebula and Jupiter underwent a modest migration (i.e. up to 0.5 AU) are the most consistent with our understanding of Vesta, even if the cases of planetesimals formed in a turbulent nebula with Jupiter undergoing limited (i.e. about 0.25 AU) or no migration cannot be ruled out. Recent results on the differentiation of the asteroid, however, raised the possibility that Vesta originally possessed a now-lost undifferentiated crust. In this case, the favoured scenarios would be those where the planetesimals formed in a quiescent nebula and Jupiter underwent a more significant migration (i.e. between 0.5 AU and 1 AU).

24 pages, 6 figures, 1 table; accepted for publication on Planetary and Space Science, to appear in the Dawn Special Issue on the Cratering on Vesta

References in corpus (5)

• Towards planetesimals: dense chondrule clumps in the protoplanetary nebula
• Vesta and Ceres: crossing the history of the Solar System
• Jovian Early Bombardment: planetesimal erosion in the inner asteroid belt
• Meteoritical and dynamical constraints on the growth mechanisms and formation times of asteroids and Jupiter
• The heating history of Vesta and the onset of differentiation

Cited by in corpus (9)

• Tracing the formation history of giant planets in protoplanetary disks with Carbon, Oxygen, Nitrogen and Sulphur
• Constraining the Cratering Chronology of Vesta
• Delivery of organics to Mars through asteroid and comet impacts
• The contamination of the surface of Vesta by impacts and the delivery of the dark material
• Dust-to-gas ratio resurgence in circumstellar disks due to the formation of giant planets: the case of HD 163296
• The Formation of Jupiter, the Jovian Early Bombardment and the Delivery of Water to the Asteroid Belt: The Case of (4) Vesta
• Olivine on Vesta as exogenous contaminants brought by impacts: Constraints from modeling Vesta's collisional history and from impact simulations
• The late accretion and erosion of Vesta's crust recorded by eucrites and diogenites as an astrochemical window into the formation of Jupiter and the early evolution of the Solar System
• Asteroid 4 Vesta: dynamical and collisional evolution during the Late Heavy Bombardment