What Is Earth Accretion?


Quick Answer

Earth and other solid planets are presumed to have formed through the process known as accretion, in which the sun-orbiting objects collided and formed progressively larger bodies. Planetary accretion began within a disk of dust and gas (primarily hydrogen) revolving around the Sun. The gas and dust were a by-product of the collapse of the molecular cloud core during the formation of the Sun.

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Full Answer

It's thought that as the gas of the solar nebula cooled with time, mineral grains condensed and aggregated to create the earliest meteoric material. Anomalous isotopic concentrations of a few meteorites suggest that development of these bodies sometimes incorporated solid material not belonging to the solar system, which existed before the formation of the Sun.

Formation of the Earth and other terrestrial planets of the solar system began 4.56 billion years ago, and it happened on a time scale of approximately 100 million years. The energy from the collisions of bodies the size of the moon led to large-scale melting and formed deep "magma oceans". These magma oceans enabled the separation of liquid metal from liquid silicate, which then sank and accumulated to form the metallic core of the planet. The collisions during accretion determined the chemistry of the mantle.

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