A general spectral slope-exposure relation for S-type main belt and near-earth asteroids

We present a general and significant relation between the spectral slope of silicate-rich asteroids (both main-belt and near-Earth asteroids) and the exposure to space weathering, computed taking into account the age and the distance from the Sun. We find strong evidence for the existence of a slope-distance relation that may identify the dominant space-weathering processes as Sun-related. In turn, the age estimates depend on various parameters and in particular on the effectiveness of the Yarkovsky-driven orbital mobility. We show that values of the parameters of the Yarkovsky effect consistent with recent experimental measurements can lead to a unique slope-age relation for main-belt and near-Earth asteroids.