The little garden demonstrates the potential benefits and limitations of farming on the moon.
For a plant, that's one modest stem, but for plant science, it's a big leap.
The first seedlings ever seeded in lunar dirt have sprouted in a tiny, lab-grown garden. This little crop, which was sown in Apollo mission samples, gives hope that astronauts would be able to cultivate their own food on the moon in the future.
Plants potted in lunar dirt, on the other hand, developed more slowly and were scrawnier than those growing in volcanic material from Earth, according to a study published in Communications Biology on May 12th. This shows that farming on the moon would necessitate far more than a green thumb.
“Ah! Richard Barker, an astrobotanist at the University of Wisconsin–Madison, said of the experiment, "It's so cool!"
"Botanists have been asking what would happen if you cultivated plants in these samples ever since they came back," adds Barker, who was not involved in the study. "However, everyone understands that those priceless samples... are priceless, which is why [NASA] was hesitant to disclose them."
Now, NASA's Artemis program, which will send men back to the moon, has provided a fresh incentive to analyze that valuable dirt and see how lunar resources could support long-term missions (SN: 7/15/19).
The soil that blankets the moon, known as regolith, is a gardener's worst nightmare. This thin powder of razor-sharp particles is made up entirely of metallic iron, rather than the oxidized form that plants prefer (SN: 9/15/20). It's also littered with microscopic glass fragments shattered by space debris slamming onto the moon. It lacks nitrogen, phosphorus, and a variety of other nutrients that plants require to thrive. So, while scientists have grown very adept at persuading plants to grow in artificial moon dust composed of terrestrial materials, no one knew if newborn plants could put down their fragile roots in the actual thing.
A group of researchers from the University of Florida in Gainesville tested thale cress to find out (Arabidopsis thaliana). This well-studied plant belongs to the mustard family and can grow in as little as a clod of dirt. Because the researchers only had a small portion of the moon to work with, this was crucial.
Seeds were planted in little pots containing about a gram of earth apiece. Four pots contained Apollo 11 samples, four pots had Apollo 12 samples, and four pots contained Apollo 17 dirt. Another 16 pots were filled with earthly volcanic material that had previously been used to simulate moon dirt in previous studies. All of the plants were grown in the lab under LED lights and nourished with a nutrient broth.
"Nothing compares to seeing the seedlings emerging in the lunar regolith for the first time," says Anna-Lisa Paul, a plant molecular biologist. "To be able to declare that we're observing the very first terrestrial life to grow on extraterrestrial elements was a moving event." And it was incredible. "Wonderful."
Plants flourished in all of the lunar dirt pots, but none of them grew as well as those grown in earthly soil. "The ones who were the healthiest were just smaller," Paul explains. The sickest moon-grown plants were small and had purplish pigmentation, which is a sign of stress. The plants growing in Apollo 11 samples, which had spent the greatest time on the moon's surface, were the most stunted.
Paul and his colleagues examined the genes in their little alien Eden as well. "Knowing what genes are turned on and off in response to a stimulus reveals you what metabolic tools plants are drawing out of their toolbox to deal with that stress," she says. All of the plants that were cultivated in moon dirt produced genetic tools that are generally found in plants that are stressed by salt, metals, or reactive oxygen species (SN: 9/8/21).
The most severely stressed genetic profile was found in Apollo 11 seedlings, providing fresh evidence that regolith exposed to the lunar surface for longer periods of time — and so littered with more impact glass and metallic iron — is more harmful to plants.
Future space explorers may be able to determine the location of their lunar residence based on this information. Perhaps lunar dirt could be tweaked in some way to make it more plant-friendly. Alternatively, plants could be genetically modified to adapt to alien soil. "We can also select plants that will perform better," Paul adds. "Perhaps spinach plants, which are extremely salt-tolerant, would thrive in the lunar regolith."
The problems that this first attempt at lunar gardening promises don't intimidate Barker. He claims that "many, many steps and pieces of technology must be established before humanity can truly engage in lunar agriculture." "However, having this dataset is critical for those of us who believe it is both achievable and important."
A-L. Paul, S.M. Elardo and R. Ferl. Plants were grown in Apollo lunar regolith present stress-associated transcriptomes that inform prospects for lunar exploration. Communications Biology. Published online May 12, 2022. DOI: 10.1038/s42003-022-03334-8.