Composition of the Earth's Core

Abstract

Models for the chemical composition of the Earth's core are developed by comparing geophysical and geochemical observations with material properties from laboratory experiments and theoretical simulations. Iron (Fe) is the predominant constituent of the core, making up more than 85% of its mass. Nickel (Ni) and sulfur (S) are major elements of the core at about 5wt% and 2wt%, respectively. At least one other light element among silicon (S), oxygen (O), carbon (C), and hydrogen (H), possibly a combination of them, is present as a significant level to match the density of the core. The core contains more than 99% of the Earth's highly siderophile elements, including nearly all the noble metals. It is virtually devoid of highly lithophile elements, such as the rare-earth elements. Identifying the principal light elements in the Earth's core and testing the current models require improved understanding of materials properties with realistic compositions at relevant pressure and temperature conditions, and tighter constraints on the process of Earth's accretion and core formation.