Abstract
New models focus on the formation of planetary embryos from a ring of planetesimals. They show that interactions with gas lead to the dispersion and migration of the embryos, which therefore do not remain confined within the initial ring. To explain the formation of terrestrial planets, it is thus necessary to postulate a specific distribution of gas that allows the embryos to be confined through convergent migration. However, the chemical and isotopic diversity observed among the terrestrial planets is difficult to explain if all the initial bodies were confined within a narrow ring, since they would have had to exhibit relatively homogeneous compositional characteristics. We will see how an influx of exotic material from the asteroid belt, during gas depletion, can contribute in varying proportions to the formation of the various planets.
