Perchlorate-Rich Martian Regolith Analogs: Effects on Terrestrial Cereal Proxies and Implications for Surface Habitability and Bioregenerative Life-Support Systems

Abstract

A better understanding of Martian surface chemistry and its implications for habitability and in-situ resource utilization is required for long-term human Mars exploration and settlement. Perchlorate salts, especially magnesium perchlorate, are most limiting geochemical constraints for the Martian surface, impact water stability, oxidation potential and the ability of any biological system placed on the Martian regolith. The Martian regolith analog in this case was made by altering terrestrial soil to mimic important physicochemical properties of the Martian surface material, such as having a high pH, low organic carbon, low bulk density, and being contaminated with perchlorate.

The limits of biological activity in perchlorate-bearing substrates were defined using two terrestrial cereal species that are known to be stress-tolerant, Pennisetum glaucum and Setaria italica. Biological stress was measured as growth, chlorosis, water uptake, and survival time and magnesium perchlorate was applied in controlled environmental conditions of closed bioregenerative habitats at 0.1-0.6% (w/v). High and strong perchlorate biological inhibition was found, with perchlorate concentration greater than 0.3% causing severe physiological impairment. The findings suggest that perchlorate contamination is a significant chemical obstacle to sustained biological activity on Mars, and highlight the importance of pre-treatment of regolith for future mission architectures and habitat design