They grow plants on land from the Moon

An undecorated UPS box containing twelve grams of lunar material arrived at Robert Ferl’s lab. Ferl, a horticulturist at the University of Florida, had been waiting for this moment for more than a decade. The small box, postmarked by NASA, contained some of the last unopened samples of moondust, or regolith, collected by astronauts on the Apollo 11, 12 and 17 missions. Ferl recalls that despite months of practice, His hands were still shaking as he picked up the sample. “It’s a strange feeling, it scares you. What if you drop it?” he asks. Ferl and his team were about to become the first researchers to grow plants in real lunar soil.

The experiment was given the green light as part of a recent lunar research boom fueled by NASA’s Artemis program, which aims to send humans to our satellite by the end of this decade. The idea is to explore the Moon in a more sustainable way by creating surface outposts intended for longer stays, as well as a space station called Gateway that will orbit the Moon – according to the space agency, both tests will be crucial for eventual trips. astronauts to Mars. Scientists believe that those longer missions will need a sustainable source of food. “Human exploration continues thanks to the ability to keep crews fed,” explains Gil Cauthorn, a researcher at the Osaka-based International Astrobotany Research Initiative.

Ferl’s research, which was published in Communications Biology in May, marks a critical first step in that direction and shows that plants can ultimately grow on lunar soil. However, without adding anything else to the regolith, the seedlings failed to thrive, indicating that future lunar farmers will need to fertilize the soil before planting crops.

To test the lunar soil, Ferl and his team divided the samples into 12 pots of 900 milligrams each and planted seeds of Arabidopsis thaliana (a hardy relative of mustard and cabbage that is considered a “model organism” in biology and is widely used). To the joy of the researchers, all the seeds germinated successfully. But the seedlings had difficulty in the next phase of growth: establishing a healthy root system. “It was quite problematic,” says Ferl. Shoots were slow growing and showed signs of high stress due to excess salt and metals, as well as intense soil oxidation. In large part, these problems are related to the conditions for the formation of the lunar regolith, which was bombarded by solar winds, cosmic rays and meteorites for billions of years. However, the lack of some ingredients, especially water and microbes, is also decisive.

Microbes are among the most important components of any soil. “They play a critical role,” says Gretchen North, an ecologist specializing in plant physiology at Occidental College who was not involved in the study. Symbiotic bacteria allow plants to regulate growth hormones, fight pathogens, minimize environmental stress, and absorb critical nutrients like nitrogen. However, the lunar regolith lacks a natural microbiome. In the absence of this complex biological network, plants grown in the regolith had trouble managing nutrient uptake and stress.

In addition, the lack of water can change the consistency of the soil in an unfavorable way. Regolith, a non-biological material, can become as dense as cement when water is added to it. “It’s hard to keep that material from turning into rock,” says Cauthorn.

But that doesn’t necessarily mean lunar regolith can’t be turned into arable soil if nutrients or compost are added to it to facilitate microbial growth. Even leaving the soil as it is, the plants may have survived for a generation or two while they became established. “Crop plants are really capable of tightening their belts and getting small,” explains North. Still, if good soil isn’t developed, “after a while they would stop fulfilling the important functions we want.”

Despite the nutritional and microbial hurdles posed by lunar agriculture, North, who has studied plant growth in simulated Martian conditions, believes the Moon offers more fertile ground than the Red Planet’s rusty soil. And it is that the Martian regolith has a high content of perchlorate, an oxidizing compound that hinders the growth of plants and can be harmful to humans.

Sooner or later, the ability to farm beyond Earth will be crucial to living and working in space. Whether in orbital habitats or long-term interplanetary travel, plants could not only be a sustainable source of food but also useful components of a life-sustaining system thanks to their production of oxygen and their ability to remove oxygen from the air. excess carbon dioxide. “Growing plants is part of the learning process to be able to survive and thrive in the space environment in which you expect to work,” said Jake Bleacher, chief exploration scientist for NASA’s Human Exploration and Operations Mission Directorate. who also did not participate in the study. In addition, farming methods in the extraterrestrial regolith could also be useful for managing agriculture on terrestrial soils that are extremely poor in nutrients and water.

“Most of us are not going to go to space,” says Cauthorn. “But if we can design a method that can produce this type of crop in an environment as hostile as the lunar surface, we could apply it to meet our food challenges in regions where food can no longer be grown.”

In the future, Ferl would like to continue studying how life might take hold in otherwise barren alien soil. But for now, he and his fellow researchers are grateful to have had the chance to experiment with one of the few lunar soil samples on Earth. “For us it has been and continues to be a real privilege,” he says.

Joanna Thompson

Reference: “Plants grown in Apollo lunar regolith present stress-associated transcriptomes that inform prospects for lunar exploration.». Anna-Lisa Paul et al. in Communications Biology, vol. 5, art. 382, May 12, 2022.

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