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J-M. Petit, A. Morbidelli (Observatoire de la Cote d'Azur - CNRS, France), J.E. Chambers (Armagh Observatory, UK), J.I. Lunine (LPL, USA), F. Robert (Museum d'Histoire Naturelle, France), G.B. Valsecchi (IAS - CNR, Italy), K.E. Cyr (NASA Johnson Space Center, USA)
We begin our numerical study of the formation of the terrestrial planets assumimg the presence of planetary embryos spread between ~0.5 and 4 AU at the time of formation of Jupiter or its core. Due to their mutual gravitational interaction and with the growing Jupiter, the orbits of the embryos begin to cross each other and they collide, forming bigger bodies. A few planets are formed in a stable configuration in the terrestrial planet region, while the asteroid belt is usually cleared of embryos. Due to the combined gravitational influence of Jupiter and of the embryos, most of the asteroids are ejected from the system in a very short time (~1 My).
Less than 1% of the asteroids survive, mostly in the 2.8-3.3 region, and their eccentricity and inclination distributions qualitatively resemble those observed. The surviving particles have undergone changes in semi-major axis of several tenth of an AU, which could explain the radial mixing of asteroid taxonomic types. Some of the particles end up on very inclined eccentric orbits in the inner Solar System, on orbits with a longer decay time. These particles could be the source of the Late Heavy Bombardment.
In this scenario, the Earth would continuously accrete water during its formation, from the earliest phases when the solar nebula was still present, to the late stages of gas-free sweepup of scattered planetesimals. Asteroids and the comets from the Jupiter-Saturn region were the first water deliverers, when the Earth was less than half its present mass. The bulk of the water presently on Earth was carried by a few planetary embryos, originally formed in the outer asteroid belt and accreted by the Earth at the late stages of its formation. Finally , a late veneer, accounting for at most 10% of the present water mass, occurred due to comets from the Uranus-Neptune region and from the Kuiper belt.
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