Secular Resonances in the Inner Solar System

P. Michel (Obs. Côte d'Azur)

Many studies have shown that secular resonances are very effective to transport asteroids from the main belt to the planetary-crossing region. Recently, a semianalytical study based on the expansion of the Hamiltonian of the N-body problem with respect to planetary orbital eccentricities and inclinations has allowed to obtain the first location of the linear secular resonances in the inner Solar System (semimajor axes smaller than 2 AU), i.e. where many Near-Earth Asteroids (NEAs) evolve. The results show that all these resonances, as well as the Kozai one, are present and that some can even overlap. Moreover, a resonant model has been derived for each resonance in order to study their effect. It appears that the secular resonances involving inner planets' orbital frequencies (i) can cause great variations of eccentricities and inclinations, (ii) provide a transport mechanism from the Mars-crossing region to the Earth-crossing one and (iii) can lead NEAs to highly-inclined orbits. Moreover, the overlapping of two resonances can lead to large scale chaos. The dynamics of NEAs can thus be affected by several mechanisms and therefore, secular resonances must be taken into account to study their evolutions since they could partly explain the observed orbital distributions and lifetimes of these objects.