More than 50 years after astronauts brought the last lunar rock samples to Earth, scientists have succeeded in growing plants in lunar soil for the first time from three Apollo missions.
All the moon– Soil plants grew slowly and relatively poorly, but those grown in samples that had been more exposed on the lunar surface tended to do the worst, and genetic analysis showed changes indicative of stress. Low growth could be concerning: As NASA prepares to send astronauts back to the moon with its Artemis program – and possibly even to Mars – being able to grow food in alien soil for long missions will become increasingly important.
“The ability to successfully take plants with us to the moon is… how we will grow our own food [and] how we’re going to stay there for a while without restocking,” said Robert Ferl, professor of horticultural science at the University of Florida and author of the study, during a virtual press conference on Wednesday (May 11). He also noted that growing plants on the moon could have other potential uses, including purifying the air, removing the carbon dioxide that humans exhale, and producing clean water.
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For this study, the researchers used samples of lunar soil, called regolith, collected during Apollo 11, 12 and 17between 1969 and 1972. In all three samples, they grew a common laboratory specimen, a small plant called Thale cress (Arabidopsis thaliana). For comparison, the scientists also grew Thale’s watercress in a type of soil made from volcanic ash found on Earth, called JSC-1A by NASA, meant to simulate lunar soil, which is powdery and full of fragments of abrasive glass.
“The fragments are actually quite sharp and angular,” Stephen Elardo, a geologist at the University of Florida and author of the study, said at the press conference. The lunar soil also contains bits of metallic iron, and the glass fragments trap pockets of gas, which the volcanic ash does not fully replicate.
The researchers were able to grow Arabidopsis in all three samples. Plants fared the least well in Apollo 11’s soil, which was the most “mature,” meaning the soil had been most exposed to the lunar surface. (Because the moon has no protective atmosphere like Earth‘s, its surface is hammered by meteorites, the fragments of atoms that scientists call cosmic rays and the constant stream of charged particles streaming from the sun.) Plants grew best in the Apollo 12 sample, which was less mature, and in the Apollo 17 sample, which was the least mature.
All of the plants grown in the lab-made volcanic ash grew significantly faster and bigger than any of the lunar soils.
Additionally, genetic analysis of the plants revealed that compared to plants grown in volcanic ash, those grown in lunar soil expressed many genes related to salt, metal-associated, and oxidative stress.
Apollo 11 plants expressed changes in 465 genes, while Apollo 12 plants expressed 265 genes at different rates and Apollo 17 plants 113. Most of these changes were stress-related. When they grouped the plants by appearance, they found that the plants that looked the worst – tiny and reddish-black in color – also had the most genetic changes associated with stress.
The results suggest that soil more exposed to the lunar surface is worse for plants, which may be due to changes caused by exposure to cosmic rays and solar wind, the researchers wrote. If true, the researchers say, soil in younger parts of the moon might be more effective at growing healthy plants. Although even the healthiest of these plants are stunted and slow growing, the food they produce would not necessarily be harmful and could still be nutritious. In fact, many types of dark-pigmented produce, such as cranberries and blueberries, are valued for their antioxidants produced in response to oxidative stress.
Eating plants grown in lunar soil like this may “not pose a threat to humans,” Anna-Lisa Paul, a horticulture scientist at the University of Florida, said at the press conference. “It’s hard to say, but it’s more likely that the chemicals that plants produce in response to stresses are the ones that help human stresses as well.” She said future research would be needed to explore how lunar soil might impact the nutritional value and quality of foods grown in that soil.
It also emerges from this research, the scientists said, that the simulated lunar soil is not an effective substitute for the real thing in an experiment like this, despite some similarities. Growing plants in lunar soil constantly changes its chemistry, which is why an experiment like this has never been done before with the “precious natural treasures” that are the Apollo samples, Paul said. But the exact chemistry of lunar soil is unique and can provide scientists with information that simulated soil could never provide.
“The devil is in the details,” Elardo said. “And plants are preoccupied with details.”
The research has been published May 12 in the journal Communications Biology.
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