Collisions among near-Earth asteroids (NEAs) are less frequent than those involving pairs of main belt (MB) objects; however, the orbits of many NEAs are partially within the MB. Thus the collisional evolution of NEAs is often dominated by collisions with MB asteroids and, thus, these collisions are not less intense than collisions among MB bodies. In particular, the relative velocity of collisions is usually larger. In this Letter we discuss the dependence of collisional processes of NEAs on their orbital parameters, showing that the collisions are more frequent for low inclinations and for semimajor axes and eccentricities entailing an aphelic distance of about 2.75 au. The collisions may also affect the space-weathering processes: the surface involved in an impact and, eventually, in the re-accumulation of the related ejecta, is somehow refreshed, and the spectral reddening - in particular of the S-complex asteroids - is slowed down. This process may complement the already known refreshing due to close planetary passes. If the process is relevant, an anticorrelation between the visible spectral slope of S-complex NEAs and the estimated intensity of collisional processes should be found. An analysis of the available data confirms the suggested anticorrelation.
Collisional evolution of near-Earth asteroids and refreshing of the space-weathering effects
PAOLICCHI, PAOLO
2011-01-01
Abstract
Collisions among near-Earth asteroids (NEAs) are less frequent than those involving pairs of main belt (MB) objects; however, the orbits of many NEAs are partially within the MB. Thus the collisional evolution of NEAs is often dominated by collisions with MB asteroids and, thus, these collisions are not less intense than collisions among MB bodies. In particular, the relative velocity of collisions is usually larger. In this Letter we discuss the dependence of collisional processes of NEAs on their orbital parameters, showing that the collisions are more frequent for low inclinations and for semimajor axes and eccentricities entailing an aphelic distance of about 2.75 au. The collisions may also affect the space-weathering processes: the surface involved in an impact and, eventually, in the re-accumulation of the related ejecta, is somehow refreshed, and the spectral reddening - in particular of the S-complex asteroids - is slowed down. This process may complement the already known refreshing due to close planetary passes. If the process is relevant, an anticorrelation between the visible spectral slope of S-complex NEAs and the estimated intensity of collisional processes should be found. An analysis of the available data confirms the suggested anticorrelation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
