Spectroscopic Properties of Asteroid Families

Asteroid families have been the target of several dedicated campaigns of spectroscopic observations during the last 10 years. Preliminary studies were mainly devoted to obtain a confirmation of the cosmochemical reliability of groupings identified by purely statistical analyses of the distributions of objects in the space of the orbital proper elements. These early attempts led to some spectacular confirmations of the common collisional origin of some families, like that associated with 4 Vesta. Subsequently, spectroscopic investigations started to be mostly focused on the issue of characterizing the overall mineralogical compositions of different families, at the same time looking for possible evidence of thermal differentiation of the original parent bodies and for possible evidence of ongoing space-weathering processes. Spectroscopy has also proven to be crucially needed to identify likely interlopers that can seriously affect the derived size distributions of families and the reconstruction of the original fields of ejection velocity of the fragments. At the same time, spectroscopic properties have been recognized as an invaluable tool to assess the real memberships of families mutually overlapping in the space of proper elements. Moreover, spectroscopic surveys have in general been found to be an excellent complement to conventional family searches purely based on the identification of concentrations of objects in the proper-element space. A challenging unsolved problem comes from the fact that several families have been found to exhibit peculiar spectroscopic properties. This opens up new exciting possibilities for future developments in the interpretation of asteroid taxonomic classes.