Dynamical sources and evolutions of different populations of
Earth-crossers
P. Michel
Observatoire de la Cote d'Azur, France
Recent dynamical studies have allowed to identify the main sources of
near-Earth asteroids (NEAs). These sources are main belt bodies
injected into the main resonances of the asteroid belt, and Mars-crosser
asteroids, which are themselves transported from the main belt to
Mars-crossing orbits through high order resonances. We will first recall the
different dynamical mechanisms which allow to transport small bodies from
these sources to Earth-crossing orbits. Considering a scenario in which the
Earth-crosser population is maintained in a steady-state (as suggested
by the number and ages of lunar craters), we will present different results
on the orbital distribution of the Earth-crosser populations coming from
each source, and their dynamical evolutions. In particular, we will show how
some objects can be transported in regions in which no asteroid has been
discovered yet (e.g. inside Earth's orbit), and their dynamical evolutions in
these regions. A good understanding of observational biases as well as
new observational surveys are thus required to complete the inventory
of the NEA population, to improve the knowledge of their real orbital
distribution as well as to better estimate the contribution of each of
their potential sources providing the same resulting distribution.