Martian Aqua: Occurrence of Water and Appraisal of Acquisition Technologies

The production of water through in-situ resource utilization (ISRU) will be necessary for a sustainable human presence on Mars. Accessible water on Mars occurs as ice (pure and mixed with regolith), bounded water in the regolith (adsorbed and in hydrated minerals) and vapor in the atmosphere. Harvesting water from the atmosphere appears to be relatively challenging than obtaining it from the regolith. However, the potential landing sites for human exploration are unlikely to have easy access to near-surface ice of any form, while utilization of the atmosphere can be accomplished almost anywhere. Extensive research has been conducted on atmospheric water vapor, which is ubiquitous and renewable, yet provides only a thin water source across the planet. This paper provides an overview of water availability on Mars, investigates the volatiles (CO 2 , H 2 O) phase equilibria in the atmosphere-surface system of the planet, and compares water harvesting from the atmosphere to obtaining water from the regolith. The findings indicate that while atmospheric water harvesting does not appear to be feasible to serve as the primary water source, it might have potential to become a supplementary, decentralized clean water supply. Atmospheric water harvesting systems on Mars require more power and energy, but they offer greater simplicity and flexibility compared to water extraction from the regolith. This approach could prove valuable in regions where water extraction from the regolith is infeasible or as a temporary backup in the event of a primary water system failure. Such a distributed water harvesting method might enhance the resilience and flexibility of water supply systems for future human Mars missions and settlements. Ultimately, any technology developed for extraterrestrial environments can have important applications on Earth.