Evolution of planet crossing asteroids in the inner Main Belt

We studied the dynamical evolution of asteroids in terrestrial planet crossing orbits, located between 2.1 and 2.5 AU. The evolution is analyzed by direct numerical integration of massless particles under the gravitational influence of all planets from Venus to Neptune. The simulations include the Yarkovsky effect, introduced as a non conservative force that produces a slow variation of the average orbital semimajor axis. Our analysis focuses on the test particles that can reach the middle and outer regions of the Main Belt (semimajor axis > 2.5 AU) during their evolution, since these may be relevant for understanding the transport mechanisms of asteroids from the inner Belt. These mechanisms could help to explain, for example, the existence of basaltic asteroids beyond 2.5 AU assuming that these bodies originate in the Vesta family, located at ∼ 2.3 AU. We found that, although some orbits that reach the middle and outer regions of the Belt can become temporarily detached from the planet crossing regime, and may have their orbital eccentricities damped due to capture at some mean motion resonances, such orbits survive for only a few hundred thousand years and, ultimately, the test particles return to the planet crossing regime being eventually discarded by close encounters with the planets. These results seem to indicate that a transport mechanism based only on planetary encounters and resonant capture might not be efficient enough to justify the presence of basaltic asteroids beyond 2.5 AU.