Dynamical Structure of the 2/1 Commensurability with Jupiter and the Origin of the Resonant Asteroids
Using a semi-analytic approach, we provide a three-dimensional picture of the secular dynamics in the 2/1 mean-motion commensurability, mapping the most chaotic regions and the two islands ofquasi-regularmotion. Five asteroids have recently been discovered in one of these islands and it has been conjectured that they were injected by the Themis-family formation event, which occurred close to the 2/1 resonance border. We show that this scenario is viable from the orbital and size distribution point of view and that it would also explain why no asteroids have been observed in the second island. Finally we discuss the possibility that the 2/1 resonance is the dominating source of CI and CM meteorites, as was suggested on spectroscopical bases. We find that the efficiency of the 2/1 resonance is far too small for it to be such a dominating source.