SPHERE Unveils the True Face of the Largest Main Belt Asteroids

International audienceOver the past 2.5 years, we have been carrying out disc-resolved observations of a substantial fraction of all large (D > 100 km) main-belt asteroids, monitoring them at high angular resolution throughout their rotation, and sampling the main compositional classes, using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on the VLT. These observations enable us to characterise the internal structure of our targets from their density as well as their cratering record down to ~ 30 km in diameter. Such information, in turn, places unprecedented constraints on models of the formation of the Solar System and the collisional evolution of the main belt