The team used a commercial lunar regolith simulant supplied by Exolith Labs, formulated to resemble the composition of samples collected by Apollo astronauts. Lunar regolith lacks organic matter and soil microorganisms, but it contains a range of minerals and essential plant nutrients along with potentially toxic heavy metals. To address these limitations, the researchers focused on strategies that can convert the sterile regolith simulant into a more soil-like medium suitable for plant growth.
The experiment centered on the Myles variety of chickpea, a compact and resilient type selected for its suitability for cultivation under space constrained conditions. Before planting, the scientists coated the chickpea seeds with arbuscular mycorrhizae, a group of fungi that form symbiotic relationships with plant roots. These fungi help plants access nutrients while at the same time limiting the uptake of harmful elements such as heavy metals, offering a biological approach to managing the unique chemistry of lunar regolith.
To further enhance the growth medium, the team mixed the regolith simulant with vermicompost, an organic amendment produced by red wiggler earthworms as they digest waste such as food scraps, cotton based clothing and hygiene products. Vermicompost is rich in plant nutrients and hosts a diverse microbiome, making it a promising way to recycle mission waste into a useful resource for crop production. By combining regolith simulant with vermicompost in different proportions, the researchers tested how much of the simulated moon dirt could be used without compromising plant health.
The results showed that mixtures containing up to 75 percent lunar regolith simulant and 25 percent vermicompost were able to support chickpea plants through to harvest. At these ratios, the plants produced mature chickpeas, demonstrating that the blend provided sufficient nutrients and acceptable levels of toxic elements. When the proportion of simulant exceeded 75 percent, however, the plants displayed stress symptoms and often died prematurely, indicating that high regolith content still poses challenges for long term cultivation.
Even under stressful conditions, chickpea plants inoculated with arbuscular mycorrhizae survived longer than plants grown without the fungal partner, underscoring the importance of this symbiosis for maintaining plant health in regolith rich media. The researchers also observed that the fungi successfully colonized the chickpea roots and persisted in the simulant, suggesting that in an operational lunar greenhouse they might only need to be introduced once to establish a stable microbial community. This persistence could simplify future life support systems by reducing the need for repeated inoculation.
Although the team has now demonstrated that chickpeas can reach harvestable maturity in simulated moon soil mixtures, key questions remain about the quality and safety of the resulting crop. The scientists plan to analyze the chickpeas for nutritional content to determine whether they provide the vitamins, proteins and minerals astronauts will need during extended missions. They will also test the legumes for heavy metal accumulation to ensure that consuming them would be safe for crews living and working on the lunar surface.
"We want to understand their feasibility as a food source," said first author Jessica Atkin, a doctoral candidate in the Department of Soil and Crop Sciences at Texas A and M University. "How healthy are they? Do they have the nutrients astronauts need? If they are not safe to eat, how many generations until they are?" These questions will guide follow up experiments as the team refines its bioremediation strategies and explores other crop species that might thrive in similar conditions.
Project lead Sara Santos, a distinguished postdoctoral fellow at the University of Texas Institute for Geophysics in the Jackson School of Geosciences, emphasized that the work represents a significant step toward sustainable agriculture beyond Earth. Santos and Atkin initially funded the research themselves to test key concepts in using fungi, plants and recycled organic matter to transform regolith into productive soil. The promising early results have now secured support from a NASA FINESST grant, enabling more extensive studies of bioremediation processes and closed loop resource use for future lunar habitats.
Research Report:Bioremediation of lunar regolith simulant through mycorrhizal fungi and plant symbioses enables chickpea to see
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