... 8, ``Celestial Mechanics'', 2002 Two problems in solar systems dynamics, possible solutions and future A. Fienga IMCCE­Observatoire de Paris, Paris, France In this contribution, two major aspects of the new challenges of the solar system dynamics are presented. ... As it was demonstrated by (Standish and Fienga [4]), the perturbations of the Mars orbit by the asteroids are difficult to modelize and they present now the main limitation of the present theory of Mars motion. ...