Good news! Today, my work is published in Nature, a prominent scientific journal. The paper is entitled A deep crust-mantle boundary in the asteroid 4 Vesta and we discuss the asteroid’s internal structure combining analysis of surface observations (Dawn data) and results from numerical simulations of impacts. The EPFL press release is available here.
Asteroid 4-Vesta is a differentiated body (a body with a crust, a mantle and a core). This body could be a planetary embryo as they existed in the beginning of the solar system. Models for Vesta’s formation prevalent up to now consider a chondritic bulk composition, which implies a thin crust and a mantle enriched in olivine.
The most recent numerical simulations of impacts, taking into account the two superimposed craters in the South Pole region, predict that the crust was drilled and the mantle excavated. However, in this paper, we show using the Modified Gaussian Model (link in french) that olivine is not found in the South Pole region of Vesta, even where the deepest rocks outcrop (see Figure 1 below). Moreover, our analyzes of simulations’ results show that material enriched in olivine should have been ejected from the asteroid during the impacts, and should now be in the vestoids or in the HED meteorites that ended up on Earth. Which is not the case.
Our observations lead to the idea that the crust is significantly thicker and the mantle thinner than what was usually considered. Thus Vesta do not have a chondritic bulk composition which has major implications as one now need to reconsider the model of Vesta’s formation. One should note that other recent works support our conclusions (Consolmagno et al., ACM 2014).