Scientists are growing plants in the lunar soil, a first in human history and a milestone in lunar and space exploration.
In a new paper published in the journal communication biology, researchers at the University of Florida have shown that plants can successfully germinate and grow in lunar soil. Their research also investigated how plants respond biologically to lunar soil (also known as lunar regolith), which is quite different from the soil found on Earth.
The work is a first step toward one day growing plants for food and oxygen during lunar or space missions. More directly, the research comes as Project Artemis plans to send humans back to the moon.
“Artemis needs a better understanding of how to grow plants in space,” said Rob Ferl, co-author of the study and Distinguished Professor of Horticultural Sciences at the UF Institute for Food and Agricultural Sciences (UF/IFAS).
Plants played an important role even in the early days of lunar exploration, said study co-author Anna-Lisa Paul, professor of horticultural science at UF/IFAS.
“The plants helped determine that the soil samples brought back from the moon did not contain pathogens or other unknown components that would harm terrestrial life, but the plants were simply covered in lunar regolith and never actually grew in it,” Paul said.
Paul and Ferl are internationally recognized experts in the study of space plants. Through the UF Space Plant Laboratory, they have conducted experiments on the space shuttle, the International Space Station, and suborbital flights.
“For longer future space missions, we might use the moon as a hub or launch pad. It makes sense that we would want to use the soil that already exists to grow plants,” Fair said. “So what happens when you grow plants in lunar soil, which is completely beyond the evolutionary experience of plants? What do plants do in a lunar greenhouse? Can we have lunar farmers?”
To answer these questions, Fair and Paul devised a deceptively simple experiment: Seed in lunar soil, add water, nutrients and light, and record the results.
Complexity: Scientists have only 12 grams—just a few teaspoons—of lunar soil to use for this experiment. The soil, borrowed from NASA, was collected during the Apollo 11, 12 and 17 lunar missions. Paul and Ferl applied 3 times in 11 years, hoping for a chance to use the lunar regolith.
The small amount of soil, not to mention its immeasurable historical and scientific significance, meant that Paul and Fair had to design a small-scale, well-choreographed experiment. To grow their small lunar garden, the researchers used thimble-sized holes in plastic plates typically used to grow cells. Each well acts as a pot. Once they filled each “jar” with about a gram of lunar soil, the scientists moistened the soil with a nutrient solution and added some seeds from the Arabidopsis plant.
Arabidopsis is widely used in plant science because its genetic code has been completely mapped. Growing Arabidopsis in lunar soil allowed researchers to gain a deeper understanding of how soil affects plants, down to the level of gene expression.
As a point of comparison, the researchers also grew Arabidopsis in JSC-1A, a terrestrial material that mimics real lunar soil, and simulated Martian and terrestrial soils from extreme environments. Plants grown in these non-lunar soils were the experimental controls.
Before the experiment, researchers weren’t sure whether seeds planted in lunar soil would germinate. But almost everyone did.
“We were surprised. We didn’t expect it,” Paul said. “This tells us that the lunar soil did not interrupt the hormones and signals involved in plant germination.”
Over time, however, the researchers observed differences between the plants grown in the lunar soil and the control group. For example, some plants that grow in lunar soil are smaller, slower-growing or more diverse in size than their counterparts.
These are physical signs that plants are grappling with the chemical and structural makeup of the lunar soil, Paul explained. This was further confirmed when the researchers analyzed the gene expression patterns of the plants.
“At the genetic level, plants are using tools normally used to deal with stressors, such as salts and metals or oxidative stress, so we can infer that plants view the lunar soil environment as stressful,” Paul said. “Ultimately, we hope to use gene expression data to help address how we can improve the stress response to the level at which plants — especially crops — can grow in lunar soil with little impact on their health.”
Ferl and Paul, who collaborated on the study with UF assistant professor of geology Stephen Elardo, say the response of plants to lunar soil may be related to where the soil was collected.
For example, the researchers found that the most stressed plants were those growing in what lunar geologists call mature lunar soil. These mature soils are those that are exposed to more cosmic winds, which change their makeup. On the other hand, plants grown in relatively less mature soil performed better.
Growing plants in lunar soil could also change the soil itself, Elardo said.
“The Moon is a very, very dry place. How will the minerals in the lunar soil respond to plants growing in it, and the added water and nutrients? Will adding water make the mineralogy more plant-friendly?” Elalado said.
Subsequent research will build on these questions. Currently, scientists are celebrating their first steps towards growing plants on the moon.
“We wanted to do this experiment because we’ve been asking this question for years: Will plants grow in lunar soil,” Fehr said. “As it turns out, the answer is yes.”