Vacuum-induced oxygen extraction from Fe-bearing model minerals: implications for lunar regolith processing

Abstract Establishing a sustained human presence on the Moon requires in situ oxygen production for life support. In this study, we propose an innovative oxygen production method in which oxygen gas is generated by reducing regolith minerals under extremely low pressures, without the need for melting. We focus on iron-containing minerals because iron oxide is among the most readily reduced constituents in lunar regolith. Hematite and fayalite were selected as test materials for proof of concept, and thermodynamic analysis predicted oxygen emission by heating these materials above 1000 °C under lower pressures than 10 − 8 atm. The ground-based experiments using the hematite and fayalite pellets verified oxygen gas emission by heating under low pressures. 1 g of a hematite pellet was completely reduced to magnetite by heating at 1200 °C under 10 − 8 atm as total pressure, and 0.03 g of oxygen was removed. Then, it was thermodynamically predicted that the model composition of lunar regolith could generate oxygen gas without melting when heated at 1050–1300 °C under 10 − 15 atm by reduction of SiO 2 and FeO constituents. These results provide a proof of concept for vacuum-induced oxygen release from iron-bearing minerals and suggest its potential relevance to future lunar regolith processing.