Synchrotron facilities and the study of the Earth's deep interior

The combination of synchrotron x-ray facilities with high-pressure methods provides new experimental tools for addressing geophysical problems relevant to understanding the interior of the Earth and other planets. Among the important geophysical questions related to the Earth's silicate mantle are the origin of seismic discontinuities in the upper mantle, the rheological properties of mantle minerals and their influence on dynamic flow in the Earth, and the nature of the core-mantle boundary region. In the case of the Earth's core, key questions are centred on the identity of the light elements of the core and their effect on energetics and thermodynamic properties, the melting curve of iron and its alloys and the origin of seismic anisotropy in the inner core. Both new and established high-pressure synchrotron methods applied to the diamond anvil cell and large-volume apparatus are surveyed. Advances in synchrotron capabilities have been accompanied by new innovations in high-pressure technology. X-ray diffraction techniques are mature but continued improvements are leading to expanded pressure-temperature coverage and better ability to recover crystallographic details. Diffraction and absorption studies of the properties of liquids of silicate and iron alloy composition have expanded in response to new capabilities. Recently, methods for inelastic scattering and nuclear resonance probes have been developed at high pressures and these provide constraints on vibrational, electronic and magnetic properties, which were previously unattainable.