Probing the core's light elements

Abstract

A fine marriage between seismic data and laboratory experiments carried out at the extreme conditions of Earth's deep interior indicates that the planet's liquid outer core is poor in oxygen. See Letter p.513 Earth's liquid outer core consists mainly of liquid iron alloyed with about 10% (by weight) of light elements. Oxygen has been proposed as a major light element in the core, based on cosmochemical arguments and chemical reactions during accretion, but here Huang et al. report data that virtually rule out oxygen as a major light element in the liquid outer core. They compare density and sound-velocity measurements in shock-wave experiments in the Fe–S–O system of Earth's core with geophysical observations. Their findings are consistent with an oxygen-depleted core, and a reduced environment during early Earth accretion, with important implications for early Earth accretion models.