Surface Composition of ‘Icy’ Asteroids and the Special Case of Ceres

Meteorites have long been considered as reflections of the compositional diversity of main belt asteroids and consequently they have been used to decipher their origin, formation, and evolution. However, while some meteorites are known to sample the surfaces of metallic, rocky and hydrated asteroids (about one-third of the mass of the belt), the low-density icy asteroids (C-, P-, and D-types), representing the rest of the main belt, appear to be unsampled in our meteorite collections. Here I will provide conclusive evidence that the surface compositions of these icy bodies are compatible with those of the most common extraterrestrial materials (by mass), namely anhydrous interplanetary dust particles (IDPs) (Vernazza et al. 2015). In addition, the recent collisional break up (≤ 10 Myrs) of a pyroxene-rich IDP-like body (Beagle family), known to be the source of the prominent α dust band (Nesvorny et al. 2008), is the likely origin of the pyroxene-rich dust contamination observed at the surface of Ceres and that of metallic asteroids (Vernazza et al. 2017).