Tackling Some Issues in Planet Formation -- From Mars's Size to a Fast Formation of Neptune

The standard model of planet formation has difficulties explaining some of the features observed in our Solar System.  Of particular note, it predicts that Mars should be as massive as the Earth.  In addition, it has difficulty in building the cores of the giant planets before the nebula disappeared.  Here, I will argue that current models of planet formation are missing two important processes- planetesimal-driven migration and collisional grinding.  I will present new simulations that include these processes.  Preliminary results suggest a heretofore unknown and radical mechanism for building the outer planets.