Vesta Collisional History Revealed by Dawn: Building a Vesta Global Crater Catalog

Kurzfassung

Introduction: Vesta is a 530 km diameter differentiated rocky body in the main asteroid belt that accreted within the first few million years after the formation of the earliest solar system solids [1,2,3]. These circumstances, along with the fact that Vesta's surface is probably sampled in meteorite collections, make Vesta one of the best targets for studying the early evolution of the main belt. According to current dynamical models [4,5,6,7], Vesta early evolution took place in an environment where collisions with other asteroids were much more frequent than today. While these models can inform our interpretations of Vesta's history, detailed studies of its impact record are necessary to discriminate between these different models and determine to what extent its surface has been reworked by cratering. Dawn observations of Vesta confirm and extend the range of geologic and impact processes seen on smaller asteroids. One of the obvious features emerging from these observations is that the surface of Vesta is dominated at all scales by impact craters. The lack of many of the obliteration processes that may occur on larger bodies (e.g., erosion on Mars, Venus; lava emplacement on the Moon and Mercury) allows for greater preservation of craters on Vesta. Observed crater sizes range from the resolution limit (10s of m for the low-altitude mapping orbit) to the largest ~500- km impact basin at the south pole, called Rheasilvia. Craters excavate and expose layers of different materials, drive regolith formation, and induce mass-wasting. Here we present the first attempt to develop a global crater catalog for Vesta that can be used to assess some of the above mentioned processes.