The composition of the Earth's core remains a mystery. However, new research shows that oxygen does not have a major presence in the outer core. This has major implications for our understanding of the period when the Earth formed through the accretion of dust and clumps of matter.
With increasing depth inside the Earth, the pressure and heat also increase. As a result, materials act differently than they do on the surface. At Earth's center are a liquid outer core and a solid inner core. The light elements are thought to play an important role in driving the convection of the liquid outer core, which generates the Earth's magnetic field.
High-speed impacts can generate shock waves that raise the temperature and pressure of materials simultaneously, leading to melting of materials at pressures corresponding to those in the outer core. The team carried out shock-wave experiments on core materials, mixtures of iron, sulfur, and oxygen. They shocked these materials to the liquid state and measured their density and speed of sound traveling through them under conditions directly comparable to those of the liquid outer core.
They conclude that oxygen cannot be a major light element component of the Earth's outer core, because experiments on oxygen-rich materials do not align with geophysical observations. This supports recent models of core differentiation in early Earth under more 'reduced' (less oxidized) environments, leading to a core that is poor in oxygen.
linkRef.: Evidence for an oxygen-depleted liquid outer core of the Earth. 2011. H. Huang, et al. Nature 479: 513-516.
