Chapter 21 Planetary Growth in Gas-Free Environment : Part VI Growth of the Planets : Origin of the Solar System

概要

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Frequent high-velocity collisions occur during accumulation of planetesimals. Such violent impacts do not always lead to coagulation but often lead to cratering erosion and/or fragmentation. To examine the influence of cratering and fragmentation on planetary growth, we performed a numerical simulation of Earth's accretion process in a gas-free environment taking the impact phenomena into account. We predict collision outcomes from impact velocities and mass ratios of colliding bodies using a scaling law on impact. Evolutions of the size and the velocity distributions of planetesimals interacting through both inelastic collisions and gravitational encounters are obtained as functions of time. The results of the present numerical simulation indicate that Earth's formation interval is longer by a factor of 1.5 than that obtained for a simple accretion-only model where no impact phenomenon is taken into account, and that the mass distribution of planetesimals becomes bi-modal at the final stage of accretion. A simple estimate of energy damping associated with mutual collisions among planetesimals shows the importance of energy partition of kinetic energies of colliding bodies into fragments and ejecta.
理論物理学刊行会の論文
1989-03-10