Human sewage combined with lunar or Martian regolith could provide the necessary nutrients to grow crops on the moon and Mars, a new experiment has shown.
“In lunar and Martian outposts, organic wastes will be key to generating healthy, productive soils,” said study leader Harrison Coker of Texas A&M University in a statement. “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.”
If humans are to create permanent bases on the moon or Mars, they are going to have to learn to live off the land — especially on Mars, where the journey time to Earth is too great and the travel costs too high to rely on regular supplies, including fertilizers, from home.
Unfortunately, the dirt on the moon and Mars is not currently suitable for growing crops. Scientists refer to this dirt as “regolith” rather than soil because regolith is inorganic and, while regolith contains nutrients within minerals, those nutrients are locked away and are mostly inaccessible to life as things stand.
So researchers have been looking for ways to make those nutrients accessible and transform the dead regolith into something closer to organic soil.
In the past, scientists have taken a number of approaches to this problem, such as heat treatment, hydroponics, liquid salts (known as ionic liquids) and electro-deoxidation that on Earth is used to break down contaminants in wastewater. However, while they have met with varied levels of success, all of these methods have a common failing: they require extra chemicals, energy and technology to be imported and to constantly be replenished with fresh nutrients, leading to them being expensive processes.
So Coker and his team looked for another way to create soils for crops using in-situ resource utilization. In other words, everything would already be on hand on the moon or Mars, and none of the components of the process would need to be imported from Earth beyond the initial technology.
The components are simply regolith and the human waste produced by the astronauts. Coker and Julie Howe, also of Texas A&M, teamed up with scientists at NASA’s Kennedy Space Center in Florida, where researchers run a prototype bio-regenerative life support system (BLiSS) called the Organic Processing Assembly (OPA).
The OPA is a series of bioreactors and filters. Sewage is put in at one end, works its way through the system and comes out at the other end as a nutrient-dense effluent with the toxins filtered out.
The experiments used simulated sewage, along with simulated regoliths, one representing the moon and the other Mars. Simulants have to be used because we don’t actually have any real Martian regolith on Earth, and the samples of lunar regolith that we have are rare and precious.
Coker’s team combined the effluent produced by the OPA with the simulated regoliths and placed the two different solutions into a shaker for 24 hours, which acted to “weather” the regolith particles.
They found that the mixtures resulted in the lunar regolith simulant desorbing (i.e., releasing) significant amounts of sulfur, as well as calcium and magnesium. The Martian simulant also produced these, as well as sodium. These nutrients are then accessible to plants to feed on and grow.
Furthermore, through a microscope it could be seen that particles of simulant had been weathered in the shaker. The lunar simulant particles had tiny pits on them, while the Martian simulant particles were covered in nanoparticles. This kind of weathering is a significant step toward becoming a more soil-like material.
Plants, of course, need more varied nutrients than what was desorbed in this experiment; iron, zinc and copper are just some of the necessary nutrients that were missing.
In addition, BLiSS technology is not yet fully efficient, and the simulants used are only approximately like the real thing — real lunar and Martian regolith might respond differently. So more experiments along these lines are needed.
But the research is already piling up: The new results are just the latest in a series exploring how resources on the moon or Mars could be utilized to help astronauts live there.
In January 2025, for example, researchers revealed that crops grow better in fertilized lunar regolith rather than the Martian variety. The experiment used Milorganite, which is a brand of fertilizer made from heat-treated microbes that digest wastewater. The Martian regolith didn’t do so well in the tests, partly because it can be very dense and clay-like, which prevents oxygen from reaching plant roots.
Martian regolith also contains perchlorate, which is a strong oxidizer. Studies by researchers at the Indian Space Research Organisation have explored how two bacteria, Sporosarcina pasteurii and Chroococcidiopsis, could create a binding agent from their waste products that, when combined with guar gum, can stick particles of Martian regolith together to form a kind of brick-like material that could be used to build habitats. However, the toxicity of the perchlorate necessitated the researchers to find more robust strains of the bacteria to resist the oxidizing effects.
The same researchers have also shown how Sporosarcina pasteurii could be used in similar fashion to create brick-like materials on the moon. However, they showed that sintering a regolith mixture in a furnace produces stronger bricks than the bacteria — but such bricks are prone to cracking in lunar conditions. So their solution was to use the Sporosarcina pasteurii-derived brick material as a sealant to fill any cracks in the sintered lunar bricks.
If we are to live on the moon or Mars, it will bring a whole new meaning to the concept of living off the land and, ultimately, hopefully, make our extraterrestrial outposts as self-sufficient as possible.
Coker’s team’s findings were published on Jan. 7 in the journal ACS Earth and Space Chemistry.
