Plants Can Grow in Lunar Soil, But They Hate It

Plants after 16 days of growth, with clear differences seen between plants grown in simulated lunar soil (left) and plants grown in real lunar regolith.

Plants after 16 days of growth, with clear differences seen between plants grown in simulated lunar soil (left) and plants grown in real lunar regolith.
Photo: Tyler Jones, UF/IFAS

For the very first time, scientists have grown plants in lunar soil returned from the Apollo missions. But given the degree of stress seen in these plants, it’s unlikely we’ll be farming on the Moon anytime soon.

New to research in communications biology is the first to show that plants, in particular the Arabid (Arabidopsis thaliana), will grow in the lunar regolith.

“Think about it for a minute and the implications are staggering,” the three scientists behind the study, all from the University of Florida, wrote to me in a group email. “Terrestrial life can potentially live on the Moon, and for astronauts spending time on the Moon, plants may be used for life support in ways that have only been speculated.”

Undoubtedly, this represents a truly astonishing and unexpected result. As the scientists explained, the lunar regolith has nothing to do with the soils found on Earth, the former being sharp, abrasive and devoid of any organic elements. In addition, lunar regolith involves certain chemical states, such as those related to iron, that are not present in terrestrial soils. They are also filled with tiny shards of volcanic glass. And of course, the Moon, with its paltry atmosphere, is continuously bombarded with radiation.

Harvesting a Thale watercress plant grown in lunar soil.

Harvesting a Thale watercress plant grown in lunar soil.
Photo: Tyler Jones, UF/IFAS.

Yes, the plants grew, but that doesn’t mean they did very well. Arabidus specimens grown in lunar regolith showed signs of stress, including slow growth, low bulk, and discoloration. The team, which included horticulturist Robert Ferl of the UF Institute of Food and Agricultural Sciences, says more research will be needed if we ever hope to grow plants on the Moon using locally sourced soils. Horticulturist Anna-Lisa Paul and geologist Stephen Elardo, both of UF, are co-authors of the study.

That we would like to grow plants on the moon is understandable. Plants produce oxygen and starch while absorbing carbon dioxide and recycling water. They “complete the cycle of sustaining life here on Earth and will likely do the same when we leave Earth,” the researchers explained.

For the study, they used samples brought back from the Apollo 11, 12 and 17 missions. Iit was not easy for them to get aseize these precious materials. The team made three official requests for samples over the past 11 years, with NASA eventually obliging them and loaning them 12 grams for the experiment. It’s just a few teaspoons. Working with simulated lunar soil, scientists spent years trying to figure out the minimum amount needed to complete this experiment. A lunar simulant known as JSC-1A, which the team then used as a control substrate for the experiment, was key to this process.

“Once we knew the minimum we could work with, one gram per plant, we knew how much to ask for,” the team told me. “In order to make the study statistically robust, we needed four plants per lunar sample. This formed the basis of our sample request to NASA.

It is important to note that not all Apollo samples were created equal. The Apollo 11 samples were taken directly from the surface and are considered “mature soils” because they were exposed and churned by the cosmic winds. By comparison, the Apollo 12 and 17 samples were dug into deeper layers. In addition to the JSC-1A lunar simulator, researchers attempted to develop plants in the Earth’s volcanic ash, which also served as a control substrate.

The scientists used Arabis, a small flowering plant native to Eurasia and Africa, because its “genome has been sequenced and well mapped with respect to the function of most of its genes”, the scientists said. . This allowed them to pinpoint the specific genes used by the plant to physiologically adapt to growing in the lunar regolith. And because watercress is so small, they were able to grow the plants in a single gram of material, placed inside thimble-sized wells normally used for cell culture.

Incredibly, Arabis grew in all soil conditions tested, although slower in lunar regolith. It also took Moon plants longer to develop larger leaves, and their root systems were stunted compared to controls. These were seen as signs of stress, much like the red-black pigments seen on the plants.

The scientists also observed the rates at which the plants expressed stress-related genes, such as responses to metals and reactive oxygen-containing compounds. Apollo 11 substrate plants produced 465 of these genes, while Apollo 12 plants produced 265 and the Apollo 17 plant produced 113. This finding suggests that regolith from the surface is less ideal as a growing substrate than soils. found deeper below. The scientists say that prolonged exposure to cosmic rays and solar wind, as well as the presence of small iron particles, likely induced the stress observed in the experiments.

I asked the team about possible mitigation strategies to treat the lunar regolith in such a way that it can properly support plant life.

“Ahhh, a very important question,” they replied. “Our study suggests that some mitigation measures may be needed for very good growth. Some of this attenuation can occur by growing plants repeatedly in the same sample, letting biology condition the soil. Other more active attenuations, such as water cycling through regolith, might also work.

A key goal of NASA’s next Artemis program is to build a lasting presence on the Moon. The new paper, with its remarkable findings, puts us in the right direction towards make that happen.

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