Future human missions to the Moon and Mars will depend not only on advanced spacecraft and life-support systems but also on reliable food production. However, growing crops beyond Earth presents a major challenge because these worlds lack living soil. Their surfaces are covered with mineral-rich dust that contains almost no organic matter or nutrients required for plant growth.
A new study by scientists at Texas A&M University suggests that recycled human waste could provide an unexpected solution. Researchers found that treated wastewater derived from human waste can extract essential nutrients from Moon- and Mars-like dust, potentially transforming barren mineral material into a fertilizer source for space farming.
In laboratory experiments, scientists combined treated sewage with soil simulants designed to replicate the mineral composition of extraterrestrial environments. For lunar experiments, they used JSC-1A lunar regolith simulant developed by NASA to mimic basalt-rich lunar soil. For Mars, they used MGS-1 Martian regolith simulant based on mineral data collected by Mars rovers, including observations from Gale Crater.
The treated wastewater was produced using a system similar to the Organic Processor Assembly, which breaks down human waste through microbial digestion. Inside the system’s bioreactors, microbes convert solid waste into dissolved nutrients and salts, creating a filtered liquid that can support plant growth. Earlier experiments using this technology had already shown that it could help grow crops such as pak choi.
However, the recycled wastewater alone did not contain all the nutrients required by plants. When researchers mixed it with the lunar and Martian soil simulants, the chemistry changed significantly. As the liquid soaked into the dust, it dissolved minerals and released important plant nutrients such as sulfur, calcium, and magnesium.
These minerals are essential for plant development and could help enrich recycled water used for crop cultivation in space habitats. The findings suggest that extraterrestrial rocks may contain hidden reserves of nutrients that can be unlocked through chemical interactions with organic waste streams.
Microscopic observations also revealed that the interaction between wastewater and dust altered the surface of the mineral grains. Moon-like dust developed small pits, while Mars-like dust acquired coatings of ultra-fine particles. Scientists describe this process as weathering, in which chemical reactions gradually break down minerals.
This weathering could offer additional benefits. Lunar and Martian dust particles are known to be extremely sharp and abrasive, capable of damaging equipment and irritating human lungs. The chemical smoothing process may make the dust safer to handle and easier to work with when growing crops.
Despite these promising results, the study also highlighted challenges. Some nutrients released during the reaction did not remain dissolved in the liquid. Instead, they attached to the surface of dust particles, making them temporarily unavailable to plants. Phosphorus showed particularly strong binding behavior, especially in the Mars-like dust.
Mars dust also caused another problem: increased salinity. When treated wastewater interacted with the Martian soil simulant, minerals dissolved more aggressively, releasing higher levels of salts into the solution. Excess salt can stress plant roots, reduce water absorption, and ultimately lower crop yields.
Because of this, any agricultural system on Mars would need to carefully control salinity levels to maintain a healthy nutrient balance for plants.
The concept of recycling human waste into fertilizer fits into the broader idea of closed-loop life-support systems for space habitats. In such systems, waste materials would be continuously recycled so that nothing is discarded. Wastewater could nourish crops directly while also helping extract additional nutrients from extraterrestrial soil.
However, managing such systems in a sealed habitat would be complex. Astronauts would need to control odors, monitor microbial activity, and ensure that filters do not clog. Chemical reactions could also create mineral deposits that block pipes and equipment, requiring regular maintenance.
Researchers say future experiments will focus on growing real crops in treated lunar and Martian soil mixtures to determine how effectively plants absorb the released nutrients. Long-term studies will also examine whether the dust continues to release beneficial minerals over time or whether the initial nutrient burst fades.
The findings of the research were published in the scientific journal ACS Earth and Space Chemistry. Scientists believe the study offers a practical pathway for sustainable agriculture in future space settlements.
If successful, this approach could allow astronauts to convert waste into a valuable resource, helping them produce food and maintain long-term human habitats beyond Earth.