Obtaining the regolith itself was an arduous task, as Anna-Lisa and Paul Rob Ferl of the UF Space Plants Lab petitioned NASA three times over 11 years to be able to work with the soil. Regolith is in limited supply on Earth and is carefully stored in NASA’s Johnson Space Center, where it is kept in nitrogen to prevent oxidation and contamination. Scientists around the world are able to receive samples on loan, but NASA space biologist Sharmila Bhattacharya says that the substance is considered a very precious material. Regolith is notably different from Earth’s soil, partially because it’s bombarded by radioactive solar winds. Growing plants in it requires a fertilizing mixture called “Murashige-Skoog medium” on top of regular watering. These additions are to make up for the lack of essential nutrients in the regolith. “On Earth, ‘soil’ connotes a lot of additional things. It also has organic materials, microbial samples, remnants of other plants, and so on,” Bhattacharya says. “Whereas regolith, strictly speaking, is this material on the surface of the moon or on the surface of Mars.” NASA, who helped to fund the research, provided the team with 12 grams of regolith in 2021. These teaspoons of soil were divided into thimble-sized plastic wells typically used for cell research. After planting the seeds, scientists moved the plates of wells into terrariums within a tightly controlled growth room. Initially, the UF researchers were unsure if any seeds would sprout, as the experiment was the first of its kind. But within just 60 hours of being planted, every seed in the regolith germinated and had tiny shoots. Part of the team’s success might have come from the seeds they chose. “The Arabidopsis plant that was used for this is actually a very commonly used model organism for research on Earth’s surface, as well as in space,” Bhattacharya says. “In the past, for example, even from the NASA side, we have flown Arabidopsis on the International Space Station.” Those experiments have looked at everything from the extraorbital life cycle of greenery to the effect of gravity on plant parts. Arabidopsis plants are easy and inexpensive to grow, but they are also suitable for research thanks to their genome. The species’ entire genetic sequence is much smaller compared to other plants and is well-mapped, making it a go-to for comparative studies. When the plants in lunar regolith appeared to struggle more than the control plants (which were planted in a regolith simulant called JSC-1A), researchers took a close look at the RNA from both batches. “When this team looked at the changes in RNA, it [was] very clear that while the plant is managing to grow in this material, there were elements of stress,” Bhattacharya says. “The cells were turning on these responses like when they’re exposed to oxidative stress.” Cellular stress indicators were only one sign of growth problems. The plants grown in regolith also showed stunted growth, shorter roots, and pigmentation on the plant. The stress of growing in lunar soil manifested externally, as well as internally in the plants’ RNA. Bhattacharya says that in recent decades, the field of molecular biology has developed new tools to change cellular components in plants. If researchers are able to see exactly which gene pathways appear stressed, they can utilize genetic engineering to help plants thrive in stressful environments. Engineering or finding plants better suited for regolith growth could be the key to lunar agriculture, which Bhattacharya says is a step toward longer space flights and maybe even off-Earth settlements. But the moon isn’t quite ready for terraforming yet. Since it lacks an atmosphere, any plants grown in the vacuum of space would need to be cultivated in an enclosed space alongside humans with access to oxygen and water. With further research on proper planting procedures and the wonders of lunar soil, the moon could very well host food and oxygen by the time humans step on the moon again.
