The asteroids in the outer edge of the asteroid belt (Trojan, Hilda and Cybeles asteroids) may provide a number of clues to the origin and evolution of the asteroid belt and to the formation of our planetary system. The mid-infrared spectral region is proving to be quite diagnostic of the surface composition of primitive asteroids. In contrast with the lack of spectral structure at visible and near-infrared wavelengths, spectra of primitive asteroids exhibit clear emissivity features from which the compositional and physical properties can be inferred. In particular silicates show an emissivity high near 10 microns (the Si-O stretch fundamental). The primary goal of our proposal is to obtain Canaricam observations to characterize the surface composition (and other properties such as radius, albedo and thermal inertia) of a small sample of primitive asteroids based on their low resolution 8 - 13 microns spectra taking adantage of the unique capabilities of Canarica at GTC.