Phycoremediation leverages microalgae to remove harmful components from substrates and has been used to treat contaminated soils and wastewater, to include the removal of heavy metals. These microorganisms are powered by photosynthesis, consuming carbon dioxide and generating oxygen in the process, with few other resources required. We hypothesize that heavy metal stress is a primary inhibitor of plant growth in regolith and that this stress can be mitigated by bioremediation with photosynthetic microorganisms. We are proposing a study to assess whether the cyanobacterium Arthrospira platensis (A. platensis; common name: spirulina) can process lunar regolith into a soil suitable for crop production. We intend to combine photosynthetic metabolic modeling to optimize cyanobacterial growth on regolith, assess the ability of A. platensis to capture heavy metals, and evaluate plant growth in the remediated regolith. Our proposed work to render lunar regolith more conducive to in situ agriculture supports NASA’s Moon to Mars objectives and NASA’s Space Biology Science Plan.

Manual grinding of regolith approximates the decomposition of regolith pieces due to space weathering and micrometeor impacts. However, it’s a low energy approximation of these phenomena. We have begun a collaboration with the Vertical Gun Range at NASA Ames Research Center where we aim to use high velocity projectiles to better simulate the energy of micrometeors and generate more accurate simulants.

Next, we performed initial experiments on the microorganism we aim to use for phycoremediation: Spirulina. To this end, we first built a custom, water-cooled experimental setup to determine oxygen production by Spirulina when it is performing photosynthesis. The water-cooled setup prevents drift in the oxygen sensors due to temperature fluctuations as the light gets brighter. The resulting data was of high quality and provided the necessary experimental parameters for follow-on experiments. Finally, we verified methods to separate Spirulina from the regolith for down-stream analysis. We hypothesized that phototaxis – the ability of photosynthetic microorganisms to migrate towards a light source – could be used to separate microbes from the soil. Indeed, using targeting lighting, the Spirulina cells migrated away from the regolith towards the light, and could be isolated for additional testing. Taken together, all preliminary experiments have been completed and we are prepared to perform plant growth experiments in the coming months.

Looking forward, we will take these methods forward to accomplish the remaining objectives of this project. We anticipate being able to complete all tasks by the end of 2025.

Phycoremediation leverages microalgae to remove harmful components from substrates and has been used to treat contaminated soils and wastewater, to include the removal of heavy metals. These microorganisms are powered by photosynthesis, consuming carbon dioxide and generating oxygen in the process, with few other resources required. We hypothesize that heavy metal stress is a primary inhibitor of plant growth in regolith and that this stress can be mitigated by bioremediation with photosynthetic microorganisms. We are proposing a study to assess whether the cyanobacterium Arthrospira platensis (A. platensis; common name: spirulina) can process lunar regolith into a soil suitable for crop production. We intend to combine photosynthetic metabolic modeling to optimize cyanobacterial growth on regolith, assess the ability of A. platensis to capture heavy metals, and evaluate plant growth in the remediated regolith. Our proposed work to render lunar regolith more conducive to in situ agriculture supports NASA’s Moon to Mars objectives and NASA’s Space Biology Science Plan.