Perchlorate-Conditioning of Regolith as a Potential Phosphorus Source for a Cyanobacterial Loop

Bioregenerative life support on Mars will require the conversion of regolith into usable nutrients. While perchlorate-reducing microbes can detoxify regolith, and nitrogen-fixing cyanobacteria (like Anabaena sp. PCC 7938) can grow on regolith-derived minerals, biological production is ultimately limited by phosphorus availability. A recent 2026 study observed a marked increase in plant-available phosphorus after aerobic, but not anaerobic, conditioning of a perchlorate-bearing simulant, despite perchlorate reduction occurring under both conditions. However, that study was not designed to identify the causal mechanism of the phosphorus release, nor did it test whether the mobilized phosphorus remains bioavailable to support cyanobacterial growth. This proposal outlines a hypothesis-driven experimental design to fill this critical gap. We propose a two-reactor liquid loop system: a conditioning reactor for detoxification and potential phosphorus mobilization, and a membrane-separated photobioreactor growing Anabaena on the resulting leachate, with biomass returned as carbon and electron-donor substrate. To isolate the independent and interactive effects of perchlorate presence, active biological conditioning, carbon addition, and redox state (aerobic vs. anaerobic), the study employs a full 2 × 2 × 2 × 2 factorial design. The research sequentially addresses three questions: (A) What causes net regolith-derived phosphorus mobilization? (B) Does that mobilized phosphorus support actual cyanobacterial growth and assimilation? (C) Does the coupled process improve net phosphorus recovery relative to a defined abiotic baseline, while accounting for all resource costs (water, energy, carbon) and electron-donor balances? By applying rigorous causal attribution and mass-balance accounting, this proposal aims to determine whether perchlorate conditioning can convert otherwise inaccessible mineral phosphorus into a biologically useful resource for sustainable Mars settlement. Positive, mixed, and null outcomes are all designed to be informative.