From extraction to purification: A comprehensive review of oxygen production from lunar regolith for ISRU

Sustainable human exploration of the moon requires the ability to produce essential resources, particularly oxygen, through in-situ resource utilization (ISRU). This review provides a systematic overview of technologies for producing high-purity oxygen from lunar regolith, encompassing mineralogical characteristics, oxygen-release mechanisms, extraction pathways, and purification techniques. While oxygen production is often discussed primarily in terms of extraction, the quality and usability of the generated oxygen are strongly dependent on the subsequent purification processes, and both aspects are discussed in this work. A mineralogical–geological framework is established to elucidate the spatial distribution and thermodynamic accessibility of oxygen resources across mare, highland, and polar regions. Subsequently, the fundamental mechanisms and rate-limiting steps of eight representative extraction methods, including electrolysis of polar ice, hydrogen and methane reduction, carbothermal processing, fluorination, and molten regolith electrolysis, are analyzed, with emphasis on their operational windows and performance under lunar low-gravity, high-vacuum, and extreme thermal conditions. This review further summarizes and evaluates terrestrial progress in oxygen purification methods such as cryogenic distillation, pressure swing adsorption, membrane separation, and electrochemical oxygen pumps, assessing their potential for lunar implementation. By integrating mechanistic understanding with practical engineering constraints, this work serves as a comprehensive reference to guide the strategic development of lunar ISRU technologies.