Plants can grow in lunar soil – but they hate it

Plants can grow in lunar soil – but they hate it

The plants after 16 days of growth, with clear differences between plants growing in simulated lunar soil (left) and plants growing in real lunar regolith.

The plants after 16 days of growth, with clear differences between plants growing in simulated lunar soil (left) and plants growing in real lunar regolith.
photo: Tyler Jones, UF/IFAS

For the first time ever, scientists have grown plants in lunar soil returned from the Apollo missions. But given the level of stress seen in these plants, it’s unlikely we’ll be farming on the moon any time soon.

New research in Communications Biology shows for the first time that plants, especially thale cress (Arabidopsis thaliana), will grow in lunar regolith.

“Think about it for a minute and the effects are amazing,” the three scientists behind the study, all from the University of Florida, wrote to me in a group email. “Terrestrial life can potentially live on the moon, and for astronauts on the moon, plants can be used to support life in ways that have only been speculated about.”

Undoubtedly, this represents a truly amazing and unexpected result. As the scientists explained, lunar regolith is unrelated to soils on Earth, the former is sharp-edged, abrasive and does not contain any organic elements. In addition, lunar regolith contains certain iron-related chemical states that are not present in terrestrial soils. They are also packed with tiny shards of volcanic glass. And, of course, the moon, with its meager atmosphere, is constantly being bombarded with radiation.

Harvesting a thale cress grown in lunar soil.

Harvesting a thale cress grown in lunar soil.
photo: Tyler Jones, UF/IFAS.

Yes, the plants grew, but that doesn’t mean they grew fantastically well. The thale cress specimens grown in the lunar regolith showed signs of stress including slow growth, low volume and discoloration. The team, which included gardener Robert Ferl from the UF Institute of Food and Agricultural Sciences, says more research will be needed if we ever hope to grow crops on the moon using locally sourced soil. Gardener Anna-Lisa Paul and geologist Stephen Elardo, both from UF, are co-authors of the study.

That we want to grow plants on the moon is understandable. Plants produce oxygen and starch while absorbing carbon dioxide and recycling water. They “complete the sustainable life support cycle here on Earth and will likely do the same as we move away from Earth,” the researchers explained.

For the study, you used samples brought back from the Apollo 11, 12 and 17 missions. IIt wasn’t easy for her to get onehold these precious materials. The team made three formal requests for the samples over the past 11 years, with NASA eventually providing them with 12 grams for the experiment. That’s just a few teaspoons. Working with simulated lunar soil, scientists spent years trying to figure out the minimum amount needed to conduct this experiment. Key to this process was a lunar simulation called JSC-1A, which the team later used as a control substrate for the experiment.

“Once we knew the minimum we could work with, one gram per plant, we knew how much to charge,” the team told me. “To make the study statistically robust, we needed four plants per lunar sample. That formed the basis of our request to NASA for samples.”

Importantly, not all Apollo samples were created equal. The Apollo 11 samples were collected directly from the surface and are considered “mature soils” because they were exposed and churned by cosmic winds. In comparison, the Apollo 12 and 17 samples were dug from deeper layers. Next to the lunar simulant JSC-1A, the researchers tried to grow Plants in volcanic ash from the soil, which also served as control substrate.

The scientists used thale cress — a small flowering plant native to Eurasia and Africa — because its “genome has been sequenced and well mapped in terms of the function of most of its genes,” the scientists said. This allowed them to identify the specific genes used by the plant to physiologically adapt to growing in the lunar regolith. And because the thale cress is so tiny, they have were able to grow the plants in a single gram of material Inside thimble-sized wells typically used for culturing cells.

Incredibly, thale cress grew in all soil conditions tested, albeit more slowly in lunar regolith. The Moon plants also took longer to grow larger leaves and their root systems were stunted compared to the controls. These were taken as signs of stress, as were the reddish-black pigments observed on the plants.

The scientists also observed the rates at which the plants expressed stress-related genes, such as responses to metals and reactive oxygenates. The plants in the Apollo 11 substrate produced 465 of these genes, while the Apollo 12 plants produced 265 and the Apollo 17 plant produced 113. This finding suggests that surface mined regolith is less ideal as a growth substrate than deeper soils. The scientists say that prolonged exposure to cosmic rays and solar wind, as well as the presence of small iron particles, likely caused the stress observed in the experiments.

I asked the team about possible mitigation strategies to treat the lunar regolith in a way that allows it to properly support plant life.

“Ahhh, a very important question,” they replied. “Our study suggests that some mitigation may be needed for really good growth. Some of this mitigation can be done by repeatedly growing plants in the same sample, causing the biology to condition the soil. Other more active mitigation measures, like circulating water through the regolith, might also work.”

A key goal of NASA’s upcoming Artemis program is building a sustainable presence on the moon. The new paper points us in the right direction with its remarkable findings to let this happen.

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