Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram

We present globally optimized P–T phase diagrams up to 5,000 GPa for four fundamental planetary materials, Fe, MgO, SiO₂, and MgSiO₃, derived from logistic regression and supervised learning, together with a comprehensive phase equilibria database containing extensive experimental and computational data from the literature. These new P–T phase diagrams provide a solution to long-standing disputes about their melting curves, contributing to the refinement of models for giant planet and exoplanet interiors. Their implications extend to the prevalence of basal magma oceans in super-Earth exoplanets and the potential frozen rocky cores of giant planets, highlighting the profound effects of phase transitions on planetary structure and evolution.