MOLTENEARTH · Fluid Silicates at Extreme Conditions and the Magma Ocean

Partial melting of silicates dominates the chemical evolution of Earth today and was even more important in Earth’s earlier history. The Earth may have begun in a completely molten state, a global magma ocean, with silicate liquid extending from a dense silicate atmosphere to the boundary with the iron-rich core at a pressure of 140 GPa. Deep melt may exist in the Earth today, and the magma ocean may have left signatures of its presence. However, these signals are still uninterpretable because of a lack of basic knowledge of the behavior of fluid silicates at extreme conditions: very little is known of the physics and chemistry of fluid silicates beyond the conditions of ongoing shallow magma genesis (<3 GPa). We propose to solve this problem by constructing a comprehensive thermodynamic model (HeFESTo) of multi-component silicate melting, vaporization, and reaction with iron, and the physical properties of liquid and vapor phases over the entire pressure-temperature range relevant to Earth, including impacts and early Earth processes. To help constrain the thermodynamic model, we will perform new first principles quantum mechanical simulations in the range of pressure, temperature, composition relevant to the early Earth that have not yet been explored by experiment or theory. Simulations will include key homogeneous and heterogeneous systems of fluid silicates in liquid, vapor, supercritical, and solid forms, including simulations of pure phases, and phase coexistence. We expect HeFESTo to change our views of magma ocean evolution and lead to new scenarios of Earth’s earliest evolution. What these scenarios might be is impossible to predict as they will be shaped by still unknown aspects of the physics and chemistry of silicate liquids at extreme conditions, which the MoltenEarth project aims to discover.