That’s one small stem for a plant, one giant leap for plant science.
In a tiny, lab-grown garden, the first seeds ever sown in lunar dirt have sprouted. This small crop, planted in samples returned by Apollo missions, offers hope that astronauts could someday grow their own food on the moon.
But plants potted in lunar dirt grew more slowly and were scrawnier than others grown in volcanic material from Earth, researchers report May 12 in Communications Biology. That finding suggests that farming on the moon would take a lot more than a green thumb.
“Ah! It’s so cool!” says University of Wisconsin–Madison astrobotanist Richard Barker of the experiment.
“Ever since these samples came back, there’s been botanists that wanted to know what would happen if you grew plants in them,” says Barker, who wasn’t involved in the study. “But everyone knows those precious samples … are priceless, and so you can understand why [NASA was] reluctant to release them.”
Now, NASA’s upcoming plans to send astronauts back to the moon as part of its Artemis program have offered a new incentive to examine that precious dirt and explore how lunar resources could support long-term missions (SN: 7/15/19).
The dirt, or regolith, that covers the moon is basically a gardener’s worst nightmare. This fine powder of razor-sharp bits is full of metallic iron, rather than the oxidized kind that is palatable to plants (SN: 9/15/20). It’s also full of tiny glass shards forged by space rocks pelting the moon. What it is not full of is nitrogen, phosphorus or much else plants need to grow. So, even though scientists have gotten pretty good at coaxing plants to grow in fake moon dust made of earthly materials, no one knew whether newborn plants could put down their delicate roots in the real stuff.
To find out, a trio of researchers at the University of Florida in Gainesville ran experiments with thale cress (Arabidopsis thaliana). This well-studied plant is in the same family as mustards and can grow in just a tiny clod of material. That was key because the researchers had only a little bit of the moon to go around.
The team planted seeds in tiny pots that each held about a gram of dirt. Four pots were filled with samples returned by Apollo 11, another four with Apollo 12 samples and a final four with dirt from Apollo 17. Another 16 pots were filled with earthly volcanic material used in past experiments to mimic moon dirt. All were grown under LED lights in the lab and watered with a broth of nutrients.
“Nothing really compared to when we first saw the seedlings as they were sprouting in the lunar regolith,” says Anna-Lisa Paul, a plant molecular biologist. “That was a moving experience, to be able to say that we’re watching the very first terrestrial organisms to grow in extraterrestrial materials, ever. And it was amazing. Just amazing.”
Plants grew in all the pots of lunar dirt, but none grew as well as those cultivated in earthly material. “The healthiest ones were just smaller,” Paul says. The sickliest moon-grown plants were tiny and had purplish pigmentation — a red flag for plant stress. Plants grown in Apollo 11 samples, which had been exposed on the lunar surface the longest, were most stunted.
Paul and colleagues also inspected the genes in their mini alien Eden. “By seeing what kind of genes are turned on and turned off in response to a stress, that shows you what tools plants are pulling out of their metabolic toolbox to deal with that stress,” she says. All plants grown in moon dirt pulled out genetic tools typically seen in plants struggling with stress from salt, metals or reactive oxygen species (SN: 9/8/21).
Apollo 11 seedlings had the most severely stressed genetic profile, offering more evidence that regolith exposed to the lunar surface longer — and therefore littered with more impact glass and metallic iron — is more toxic to plants.
Future space explorers could choose the site for their lunar habitat accordingly. Perhaps lunar dirt could also be modified somehow to make it more comfortable for plants. Or plants could be genetically engineered to feel more at home in alien soil. “We can also choose plants that do better,” Paul says. “Maybe spinach plants, which are very salt-tolerant, would have no trouble growing in lunar regolith.”
Barker isn’t daunted by the challenges promised by this first attempt at lunar gardening. “There’s many, many steps and pieces of technology to be developed before humanity can really engage in lunar agriculture,” he says. “But having this particular dataset is really important for those of us that believe it’s possible and important.”