Geochemical Origins of the Earth

The Earth formed through accretion of planetesimals in 1–100 million years. Planetesimal impacts induce degassing, melting, and vaporization during accretion. The impact degassing, as well as the gravitational capture of the surrounding solar nebula gas, formed the proto-atmosphere on a growing Earth. The impact of heating and the blanketing effect of the proto-atmosphere resulted in the melting of the growing Earth and the formation of magma ponds or magma oceans. Separation of metallic iron and silicate in the magma ponds or magma oceans lead to the formation of the iron core. Also, this melting resulted in the chemical differentiation of the proto-mantle to some extent. At the last stage of accretion, steam in the proto-atmosphere condensed and formed a proto-ocean.