Light elements in the Earth’s core

Constraining the core’s composition is essential for understanding Earth accretion, core formation and sustainment of Earth’s magnetic field. outer inner exhibit a density deficit relative to pure iron, attributed presence substantial amounts low atomic number ‘light’ elements, such as sulfur, silicon, oxygen, carbon hydrogen. However, owing its inaccessibility, estimates can only be indirectly obtained by matching results from high-pressure experiments theoretical calculations with seismic observations. In this Review, we discuss properties phase relations iron alloys under high-temperature conditions relevant core. We synthesize mineral physics data cosmochemical geochemical give likely range compositions (Fe + 5% Ni 1.7% S 0–4.0% Si 0.8–5.3% O 0.2% C 0–0.26% H weight) 0–1.1% 0–2.3% 0–0.1% 0–1.3% 0–0.23% While exact remains unknown, tighter constraints on temperature better connections between solid liquid will help narrow potential light element compositions. Although elements (such S, Si, O, H) explain deficit, unknown. This Review explores their implications.