Using samples brought back from NASA’s Apollo 11, 12, and 17 missions, University of Florida biologists showed that a model terrestrial plant, Arabidopsis thaliana, can successfully germinate and grow in diverse lunar regoliths.
Germination and development of Arabidopsis thaliana in the lunar regolith: (a) germination rates were close to 100% in all sources of Apollo lunar regolith and indistinguishable from rates in JSC-1A simulant; two representative wells for JSC-1A and each Apollo site are shown; (b) the seedlings thinned from each well on day 6 or 8 indicated that root growth in lunar regolith is not as robust as in JSC-1A; (c) while germination was uniform among controls and lunar sites, the lunar regolith-grown seedlings did not thrive as compared to the JSC-1A controls; the diameter of the culture plate wells is 12.5 mm. Image credit: Paul et al., doi: 10.1038/s42003-022-03334-8.
“For future, longer space missions, we may use the Moon as a hub or launching pad. It makes sense that we would want to use the soil that’s already there to grow plants,” said Professor Rob Ferl, senior author of the study.
“So, what happens when you grow plants in lunar soil, something that is totally outside of a plant’s evolutionary experience? What would plants do in a lunar greenhouse? Could we have lunar farmers?”
To begin to answer these questions, Professor Ferl and colleagues designed a deceptively simple experiment: plant seeds in lunar soil, add water, nutrients and light, and record the results.
But they only had 12 grams — just a few teaspoons — of lunar soil with which to do this experiment.
On loan from NASA, this soil was collected during the Apollo 11, 12 and 17 missions to the Moon.
To grow their tiny lunar garden, the researchers used thimble-sized wells in plastic plates normally used to culture cells. Each well functioned as a pot.
Once they filled each pot with approximately a gram of lunar soil, the scientists moistened the soil with a nutrient solution and added a few seeds from Arabidopsis thaliana, a small flowering plant native to Eurasia and Africa.
Growing this model plant in the lunar soil allowed the authors more insight into how the soil affected the plants, down to the level of gene expression.
As points of comparison, they also planted Arabidopsis thaliana in JSC-1A, a terrestrial substance that mimics real lunar soil, as well as simulated Martian soils and terrestrial soils from extreme environments.
The plants grown in these non-lunar soils were the experiment’s control group.
Before the experiment, the researchers weren’t sure if the seeds planted in the lunar soils would sprout. But nearly all of them did.
“We were amazed. We did not predict that. That told us that the lunar soils didn’t interrupt the hormones and signals involved in plant germination,” said Professor Anna-Lisa Paul, first author of the study.
However, as time went on, the scientists observed differences between the plants grown in lunar soil and the control group.
For example, some of the plants grown in the lunar soils were smaller, grew more slowly or were more varied in size than their counterparts.
“These were all physical signs that the plants were working to cope with the chemical and structural make-up of the Moon’s soil,” Professor Paul said.
This was further confirmed when the team analyzed the plants’ gene expression patterns.
“At the genetic level, the plants were pulling out the tools typically used to cope with stressors, such as salt and metals or oxidative stress, so we can infer that the plants perceive the lunar soil environment as stressful,” Professor Paul said.
“Ultimately, we would like to use the gene expression data to help address how we can ameliorate the stress responses to the level where plants — particularly crops — are able to grow in lunar soil with very little impact to their health.”
“The Moon is a very, very dry place. How will minerals in the lunar soil respond to having a plant grown in them, with the added water and nutrients? Will adding water make the mineralogy more hospitable to plants?” said Dr. Stephen Elardo, co-author of the study.
Follow up studies will build on these questions and more. For now, the authors are celebrating having taken the first steps toward growing plants on the Moon.
“We wanted to do this experiment because, for years, we were asking this question: Would plants grow in lunar soil. The answer, it turns out, is yes,” Professor Ferl said.
A paper on the findings was published in the journal Communications Biology.
A.L. Paul et al. 2022. Plants grown in Apollo lunar regolith present stress-associated transcriptomes that inform prospects for lunar exploration. Commun Biol 5, 382; doi: 10.1038/s42003-022-03334-8