When the Artemis program returns humans to the moon in (hopefully) a few years, considerable logistics will have to be tackled to keep such vulnerable creatures alive in such a hostile environment.
Last but not least is the issue of food. Space agencies involved with the International Space Station have a long history of providing prepackaged supplies, but access to fresh food has benefits for both physical and mental health.
If lunar soil proved to be a suitable medium for growing fresh crops, that would be great. So a team of scientists used a few precious grams of real lunar samples collected during the Apollo missions to try and grow plants, especially thale cress or Arabidopsis thaliana†
“For future, longer space missions, we can use the moon as a hub or launch pad. It makes sense that we would want to use the soil that is already there to grow plants,” said horticultural scientist Rob Ferl of the University of Florida.
“So, what happens if you grow plants in lunar soil, something that is totally beyond a plant’s evolutionary experience? What would plants do in a lunar greenhouse? Can we have moon farmers?”
Well, spoiler: lunar dirt, also known as lunar regolith, isn’t very good at growing plants. But this research is just a first step toward growing plants on the moon one day in an exciting sci-fi future.
The current amount of lunar sample material here on Earth is quite small, and therefore valuable and highly valued.
Ferl and his colleagues, fellow University of Florida horticultural scientist Anna-Lisa Paul and geologist Stephen Elardo, were granted a loan of just 12 ounces of the precious stuff, after three applications over 11 years.
This required a very small, very tight experiment – a mini garden of Arabidopsis† They carefully divided their samples into 12 thimble-sized pots, to each of which was added a nutrient solution and a few seeds.
Control groups of seeds were also planted in terrestrial soil from extreme environments, and soil simulants (a terrestrial material used to simulate the properties of alien soils).
For the experiment, the team used a Martian soil simulant and a lunar simulant called JSC-1A. This is important because previous experiments have shown that plants can grow well in both types of simulants, but subtle differences can mean it’s really a different story.
Above: Plants growing in the three sets of lunar soil and the soil simulant.
That indeed seems to be the case. To the researchers’ surprise, nearly all of the seeds planted in the lunar samples sprouted, but that’s where things turned. Rather than growing merrily, the seedlings appeared smaller, slower growing and much more variable in size than the plants grown in the lunar simulant.
When the team then retrieved the plants to perform genetic analysis, they discovered why.
“On a genetic level, the plants brought out the agents commonly used to deal with stressors, such as salt and metals or oxidative stress, so we can conclude that the plants experience the lunar soil as stressful,” says Paul.
“Ultimately, we want to use the gene expression data to explore how we can enhance stress responses to the level where plants — especially crops — can grow in lunar soil with very little impact on their health.”
The lunar samples used by the researchers came from three different locations on the moon, at different depths from the surface, collected by Apollo missions 11, 12 and 17.
Interestingly, this seemed to have an effect on how well the plants responded to the soil. Those planted in the ground closest to the surface, from Apollo 11, fared worse; one plant even died. This is the layer of lunar regolite most exposed to cosmic rays and the solar wind, which damages it.
In contrast, the seeds planted in less exposed soil fared noticeably better, although the results were still not as good as plants grown in terrestrial volcanic ash. This information could help scientists figure out how best to grow plants on the moon, and develop ways to make the moon’s soil more hospitable to plants.
However, we are not quite there yet. Further research into characterizing and optimizing the lunar soil for plant growth will need to take place before we can consider using lunar dirt to grow crops. But at least now scientists have a better understanding of what they’re working with and what the next steps should be.
“We wanted to do this experiment because for years we’ve been asking this question: would plants grow on moon soil,” Ferl said. “The answer, it turns out, is yes.”
The research was published in Communication biology†