VLT’s SPHERE spies rocky and icy worlds

Séminaire IPAG de Pierre Vernazza (LAM), jeudi 25 janvier 2018 à 11h00, salle Manuel Forestini IPAG

Asteroids in our solar system are metallic, rocky and/or icy objects, ranging in size from a few meters to a few hundreds of kilometers. Whereas we now possess constraints for the surface composition of most D>100 km primordial main-belt asteroids, little is known regarding their internal structure. Yet, this is a fundamental property whose characteristics result directly from (a) their formation location, (b) their time of formation, and (c) their collisional history. Characterizing the internal structure of the main compositional classes of asteroids would therefore allow us to address entirely new questions regarding the earliest stages of planetesimal formation and their subsequent collisional and dynamical evolution. To achieve this goal, we carry out - via an ESO Large Program (LP) that was awarded 152h on VLT/SPHERE (the observations are spread over 4 semesters from April 1st, 2017 till March 30, 2019 in service mode) - disk-resolved observations of a substantial fraction of all D>100 km main-belt asteroids (sampling the four main compositional classes) at high angular resolution with VLT/SPHERE throughout their rotation. These observations will enable us to derive their volume (via their 3-D shape) which combined with already existing mass estimates will allow us to determine their bulk density and hence to characterize their internal structure. Such information will, in turn, provide unprecedented constraints on solar system formation models such as the Nice and Grand Tack models.