Early thermal history of the terrestrial planets

Abstract

There is much evidence that the Earth is a chemically differentiated body. If we assume that this was not the original state of affairs, then the differentiation of the original, presumed homogeneous body, into a zoned body consisting of a crust, mantle, and core is one of the most significant events or sequence of events that has occurred in the evolution of the Earth. A favored current hypothesis is that the planets accreted from relatively cold solid particles. The mechanics of the accretion process, the size and temperature of the accreting particles, and the rate of accretion are speculative and this limits our ability to define the initial conditions of the fully accreted planet. Estimates of the initial near-surface temperatures at the end of the major portion of the accretion stage of lunar to Earth-sized objects vary from about 100 to 1000 °K. The temperature profile in a primitive planet will be governed by the rate at which mass and, therefore, gravitational energy is added, the rate at which it can be radiated away from the surface, and the initial temperature of the accreting particles and their change of temperature during the accumulation process.

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