DELIVERY OF METEORITES THROUGH THE NU(6) SECULAR RESONANCE

The nu6 secular resonance provides an effective inner and high-inclina tion boundary to the main asteroid belt in the proper element space, a s objects inserted into it can undergo drastic secular changes of ecce ntricity and become Mars- and Earth-crossers. We have used Morbidelli' s (1993) theory for the secular evolution of the orbits lying inside t he resonance and Farinella's et al. (1993a) model for the isotropic ej ection of fragments following collisions against existing main-belt as teroids, to study the efficiency of 20 asteroids close to the nu6 reso nance as potential deliverers of planet-crossing fragments. We have fo und that several of these asteroids do inject into the resonance a sig nificant fraction of their fragments, which then have their orbital ec centricities increased up to Mars- and even Earth-crossing values. The refore some of these bodies - in particular the largest ones, like 6 H ebe, 304 Olga, 739 Mandeville and 759 Vinifera - are probably efficien t deliverers of meteorites. The time required for these fragments to b e transported into Earth-crossing orbits is typically of the order of 10(6) yr when the eccentricity is directly pumped up by the resonance to almost-equal-to 0.6, longer when Mars encounters are needed as an i ntermediate process. Other asteroids inject a substantial fraction of their fragments into the 3/1 (623 Chimaera, 1892 Lucienne) and 5/2 (63 1 Philippina, 907 Rhoda, 1222 Tina) Kirkwood gaps. All these asteroids should become the targets of detailed spectrophotometric investigatio ns, to assess their similarity to some of the known meteorite types.