ASTEROID FAMILIES CLOSE TO MEAN MOTION RESONANCES - DYNAMICAL EFFECTSAND PHYSICAL IMPLICATIONS

Among the asteroid families which can be considered very reliable acco rding to the results of the most recent and objective methods of stati stical identification, some are located very close to mean motion reso nances with Jupiter. A careful analysis of the dynamical behavior of t he candidate members in proximity of the resonances, combined with the known kinematical properties of the families at different size ranges , strongly suggests that the global structure of some families could h ave been significantly affected by the resonance proximity. This is tr ue even in the cases of mean motion resonances, which are not among th e most efficient and fastest commonly known depleters of asteroidal or bits. The most outstanding results of this paper concern the Eos and t he Themis family, affected, respectively, by the 9/4 and 2/1 resonance s. Both families seem to have been significantly depleted by these two resonances. Among the families showing a quasi-isotropic structure, G efion and Dora appear to have injected a substantial fraction of their original members into the 5/2 mean motion resonance, while Adeona see ms to have been only marginally affected by the 8/3. On the other hand , the irregular and/or complex structures of the Eunomia, Nysa, and Ma ria families prevent us from drawing any definitive conclusion. Finall y, for the family of Hygiea, a quite strong depleting role of the 2/1 resonance is also suggested. (C) 1995 Academic Press, Inc.