Processed Sewage Can Weatherize Moon and Mars Simulant Soil Into Something Plants Might Grow In

The moon and Mars are inhospitable to agriculture in an obvious way: their surfaces are covered in regolith - a dusty, rocky material with no organic matter, minimal nutrients, and particles sharp enough to damage plant roots even if seeds could germinate. Any permanent human presence on either body would need to change that. A study in ACS Earth and Space Chemistry describes one approach: using recycled sewage to chemically weather regolith simulants toward something more soil-like.

The work comes from researchers including Harrison Coker and Julie Howe, working alongside colleagues at NASA. The group is investigating how processed wastewater - run through NASA's bioregenerative life support system (BLiSS) at Kennedy Space Center - interacts with simulated versions of lunar and Martian surface material.

What BLiSS Produces and Why It Matters

Closed-loop life support is a necessity for any sustained human outpost beyond Earth. A lunar or Martian colony would generate substantial organic waste from both crew metabolic output and plant cultivation; shipping that waste back to Earth is not an option at scale. The BLiSS system at Kennedy Space Center processes sewage - in this case an artificial version for laboratory use - through a series of bioreactors and filters that convert it into a nutrient-dense liquid effluent.

That effluent is the ingredient the researchers applied to regolith. The question was whether combining it with simulated lunar or Martian surface material would produce something that could support plant growth.

What the Experiment Found

Researchers combined BLiSS effluent with lunar and Martian regolith simulants separately, shaking each combination for 24 hours and analyzing the result. The weathered simulants released significant quantities of sulfur, calcium, and magnesium - all essential plant macronutrients - along with other metals, when treated with both water and the BLiSS solution. The nutrient release was measurably greater with the BLiSS effluent than with water alone.

Microscopic analysis revealed physical changes as well. The lunar simulant developed tiny pits on particle surfaces. The Martian simulant became coated with nanoparticles. Both changes indicate weathering - the same kind of process that, over geological time on Earth, converts bare rock into soil. Both effects also reduced the sharpness of the mineral particles, which is a practical concern: raw regolith is abrasive enough to damage delicate root systems.

"In lunar and Martian outposts, organic wastes will be key to generating healthy, productive soils," said Coker, the study's first author. "By weathering simulant soils from the moon and Mars with organic waste streams, it was revealed that many essential plant nutrients can be harvested from surface minerals."

Limitations and What Comes Next

The researchers are explicit about the preliminary nature of these results. The simulants used in the experiment approximate lunar and Martian regolith but are not identical to the real thing. Actual regolith from both bodies contains reactive compounds - perchlorates in Martian soil are a well-documented challenge for agriculture - and conditions in actual surface environments differ substantially from laboratory shakers. The effluent used was an artificial sewage approximation rather than actual human waste.

The study does not demonstrate that crops can grow in weathered simulant. It demonstrates that the weathering process releases some nutrients and reduces particle abrasiveness - necessary but not sufficient conditions for cultivation. Actual plant growth experiments in weathered simulant, followed by testing in material closer to actual regolith, would be required next steps.

The research was funded by the NASA Space Technology Graduate Research Opportunities program and the Mars Campaign Office. It was published in ACS Earth and Space Chemistry.