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S. Charnoz, P. Thebault, A. Brahic, C. Ferrari (CEA Saclay)
An early proto-Jupiter may influence the formation of terrestrial planets during the phase of runaway growth. The transfer of random kinetic energy from a resonant region to the surrounding, due to collisions, increases the relative velocities in a disk of colliding planetesimals. This mechanism called "collisional diffusion" inhibits accretion. Thebault and Brahic (P.S.S., 1999) have quantitatively studied the propagation of the perturbation induced at the 2:1 Jupiter's resonance (3.27 a.u.). They have found that only a massive proto-Jupiter (300 Me, Me = Earth's mass) may stop accretion in the asteroid zone. In order to take into account all particles, including those that are close to the proto-Jupiter, a new deterministic simulation of an extended disk (5 a.u.) of colliding particles orbiting in the potential field of a central body and a protoplanet has been developed. Gas drag and fragmentation have not been included yet. Particles in the region of overlapping resonances appeared very efficient to heat-up the disk in a wide zone of few astronomical units, via a collisional diffusion mechanism. It is found that a proto-Jupiter with its present mass inhibits accretion up to the Earth's orbit in few 105 years, whereas a 10 to 50 Me proto-Jupiter may prevent accretion only in the asteroid belt. Surprisingly, even a 3 Me body prevents accretion up to its 2:1 inner resonance that acts as a secondary source of perturbations. In conclusion, the collisional diffusion induced in the vicinity of a proto-Jupiter seems to be a generic mechanism that stops accretion in a large fraction of the inner solar system, even with a low initial mass of the perturber. This inhibition may thus appear early during the formation of giant's planets core. The influence of collisional diffusion in the outer solar system is also currently under study.
The author(s) of this abstract have provided an email address for comments about the abstract: charnoz@discovery.saclay.cea.fr