CONICET | Buscador de Institutos y Recursos Humanos

The Trojan asteroids orbit about the Lagrangian points of Jupiter and theresidence times about their present location are very long for most of them.If these bodies originated in the outer Solar System, they should be mainlycomposed of water ice, but, in contrast with comets, all the volatiles closeto the surface would have been lost long ago. Irrespective of the rotationperiod, and hence the surface temperature and ice sublimation rate, a dustlayer exists always on the surface. We show that the timescale forresurfacing the entire surface of the Trojan asteroids is similar to that ofthe flattening of the red spectrum of the new dust by solar-protonirradiation. This, if the cut-off radius of the size distribution of theimpacting objects is between 1mm and 1m and its slope is -3, for the entiresize-range. Therefore, the surfaces of most Trojan asteroids should becomposed mainly of unirradiated dust.