Rob Ferl, left, and Anna-Lisa Paul looking at the plates filled part with lunar soil and part with control soils, now under LED growing lights. Image:
UF/IFAS photo by Tyler Jones
In a major breakthrough, scientists have grown plants in Moon dirt, marking the first time that seeds have ever been sown in soils from an extraterrestrial body, reports a new study. The milestone paves the way toward lunar gardens that might support future human crews on the Moon, though it’s important to note that the plants in the experiment, which were grown in three different soils returned by the Apollo 11, 12, and 17 missions, experienced stress and stunted growth compared to their counterparts planted in Earth-based materials.
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For decades, people have speculated about the possibility of growing plants in extraterrestrial regolith, which is the loose material found on the Moon and other rocky bodies, because this achievement would serve as a clear stepping stone toward a more sustainable human presence on the lunar surface, and beyond. Now, it’s been achieved, according to a study published on Thursday in the journal Communications Biology.“Plants will grow in lunar regolith!” said Robert Ferl, a distinguished professor of horticultural sciences in the University of Florida’s Institute of Food and Agricultural Sciences and senior author of the study, in an email. “Surprising? Maybe. Astounding? For sure. Terrestrial life can potentially live on the Moon, and for astronauts spending any time on the Moon, plants can be used for life support in ways that have till now have only been speculated about.”Ferl and two of his colleagues at the University of Florida, Anna-Lisa Paul and Stephen Elardo, announced in the study that “the terrestrial plant Arabidopsis thaliana,” commonly known as thale cress, “germinates and grows in diverse lunar regoliths,” though they did not grow as well as plants seeded in a fake lunar soil called JSC lunar simulant.While plants survived being dusted and rubbed with lunar samples in experiments that took place 50 years ago, hinting at their possible viability in Moon soils, Ferl noted that “there was no real way to set expectations” about the outcome of his team’s experiment with actually directly planting them in lunar soils for the first time.
“All we could do was our best process and then watch,” he said.Ferl and his colleagues were able to finally pull this notion of Moon plants from the land of speculation into reality thanks to their decade-long effort to obtain Apollo Moon samples from NASA’s Johnson Space Center Lunar Receiving Laboratory. Though there have been many studies about plant growth in fake extraterrestrial soils, called simulants, procuring the real stuff is understandably a difficult task—and one with permanent consequences in this case.“The samples are precious and it makes good sense for NASA to be very careful about lending them out for any purpose,” Ferl noted. “In addition, once these samples see some biology, they can never, ever be the same as they were on the Moon. The lunar samples can now never be used to study them as they existed on the Moon. So NASA had to take a deep breath in considering giving out samples that can essentially not be used for any other purpose.”However, Ferl added that the Artemis Program, a new plan to return humans to the Moon spearheaded by NASA, has changed the calculus for the agency. Whereas the Apollo astronauts spent, at most, a few days on the lunar surface, NASA and its Artemis partners hope to eventually send crews to live on the Moon for weeks or even months. This ambitious goal depends on greenlighting experiments like the one conducted at UF, to better inform strategies for living off the lunar land. Plus, NASA expects Artemis crews to return new Moon rocks to Earth, which should relieve some of the demand for the existing samples from the Apollo era.
That said, Ferl and his colleagues did not exactly receive full planters of lunar dirt for their experiment. NASA gave them just 12 grams total, split between the sites explored by the Apollo 11, 12, and 17 crews. To work with this small quantity, the team devised a miniature garden that sounds like something out of an otherworldly fairy tale, in which the plants were seeded in thimble-sized pots of Moon dust collected by interplanetary explorers who captured the world’s imagination a half-century ago. To that end, the incredible history and value of these regolith samples was not lost on Ferl and his colleagues.“Just imagine holding the Moon in the palm of your hand!” Ferl said. “We had practiced extensively the procedures that we employed to handle the lunar samples. Over and over again we practiced with the JSC lunar simulant. We knew what we were doing.”“But opening up those samples? Seeing, handling, being responsible for actual lunar samples? We were literally shaking,” he continued. “I am surprised that we did not just spill it all (and so glad that we did not). So, yeah, holding samples collected by Armstrong, Aldrin, Conrad, Bean, Cernan and Schmidt—while they were on the Moon—is an experience forever remembered and valued.”Arabidopsis thaliana, which is now the first bonafide lunar seedling, was selected for the experiment for a multitude of reasons: It is a model organism with a genome that is extremely well-understood, enabling the researchers to monitor nuanced variations in its genetic expressions. It is also small enough to fit into the tiny plant-boxes in the study, plus Ferl noted that the plant “has a rich history of spaceflight, having been in numerous experiments on the Space Shuttle and the International Space Station.”
While all of the plants germinated in the lunar samples, some of the Apollo sites proved to be apparently better suited for gardening than others, a difference revealed by the team’s monitoring of the seedlings’ genetic expressions. The plants sown in the Apollo 11 regolith, which was returned by Neil Armstrong and Buzz Aldrin during the first landing in the Moon’s Sea of Tranquility, fared the worst, as they activated 465 different genes compared to the simulant control. The plants grown in regolith collected in the Taurus–Littrow lunar valley by Apollo 17’s Gene Cernan and Harrison Schmitt, the last humans to walk on the Moon, were the least stressed, expressing only 113 genes at different levels. Meanwhile, the plants grown in the Apollo 12 regolith, collected by Charles “Pete” Conrad and Alan Bean from the Moon’s Oceans of Storms, expressed 265 different genes. Ferl and his colleagues think the differences in growth were caused, in part, by the varying exposures of the regolith samples to cosmic winds. Apollo 11’s landing site receives more of this weathering exposure than its counterparts, producing more abrasive materials that are not as conducive to plant growth. Even so, none of these basaltic lunar soils produced plants as healthy as those seeded in the simulant, suggesting that Moon gardens may require very special green thumbs.“A major takeaway is that lunar plant growth is very possible, yet we have to understand the challenges in order to maximize plant growth,” Ferl said. “There is work to be done, but success is seeable and reachable. The level of stresses that we see are similar to marginal agricultural lands here on Earth, and we have yet to work on mitigation strategies,” adding that “the more we learn about the response of plants the better informed those strategies will be.”“As scientists, the coming Artemis missions mark an important transition in the space and lunar exploration realm—the transition to a sustained presence on the Moon,” he concluded. “This will take science to enable that extended stay, and that extended stay means more science infrastructure on the Moon. So one major milestone would be having the kind of infrastructure on the Moon, like a lunar laboratory, where scientists would live and work.”