But your crops might get a little stressed…

NASA plans to return to the moon this decade. And this time for good. Because the intention is that the moon will eventually be continuously inhabited by astronauts. That means they should also be able to grow their own food. A pressing question is, of course, how. Because… Is the moon soil really suitable for that?

Washed on the moon

The idea is that the moon will eventually be used as a springboard for future, longer space missions – such as to Mars. “It makes sense then to grow crops on the land that is already there,” explains researcher Rob Ferl. “But what happens when you grow plants on lunar soil, something that is completely outside the evolutionary experience of a plant? In short, what do plants do in a moon greenhouse? Could we have moon farmers in the future?

Experiment

To answer all those questions, researchers in a new study designed a deceptively simple experiment: plant seeds in moon soil, add water, nutrients and light, and record the results.

Issue

The problem: The scientists only had 12 grams — just a few teaspoons — of lunar soil with which to conduct this experiment. This soil was collected during Apollo 11, 12 and 17. This small amount of lunar soil, not to mention its priceless historical and scientific significance, meant that the researchers had to design a small-scale, carefully choreographed experiment. To grow their small “moon vegetable garden,” the researchers used thimble-sized wells in plastic plates normally used to grow cells. Each well functioned as a culture pot. After filling each “pot” with about a gram of lunar soil, the scientists moistened the soil with a nutrient solution and added a few seeds of the Arabidopsis plant.

Why the Arabidopsis plant?
Arabidopsis is widely used in plant science because its genetic code has been fully mapped. Growing Arabidopsis in the lunar soil gave the researchers more insight into the influence of the soil on the plants, down to the level of gene expression.

Before the experiment, the researchers weren’t sure the seeds planted in the moon’s soil would germinate. But the team makes a surprising discovery: Nearly all the seeds sprouted, a first in human history and a milestone in the exploration of the moon and space.

germinate

“We were very surprised,” recalls researcher Anna-Lisa Paul. “We had not predicted this. It thus suggests that lunar soil apparently does not interrupt the hormones and signals involved in plant germination.”

An Arabidopsis plant germinates in moon soil. Image: UF/IFAS photo by Tyler Jones

So can we start a vegetable garden on the moon? Yes, although some caution is advised. The seedlings germinated, but the team noticed striking differences between the plants grown on lunar soil and volcanic ash. For example, some plants growing on the lunar soils were smaller, grew more slowly, and were more varied in size than their terrestrial counterparts. The ‘moon plants’ took longer to develop expanded leaves and more often had stunted roots.

stress

In short, the moon plants showed more signs of stress. “We can conclude that the plants experience the lunar soil as stressful,” says Paul. Nevertheless, we need not give up hope right now. “Ultimately, we want to use gene expression data to explore how we can improve stress responses,” the researcher continues. “Then we can grow plants – especially crops – on lunar soil without impacting their health.”

The Moon Bottom

How plants respond to lunar soil may also be related to where exactly the soil was collected. For example, the researchers found that plantlets sown in Apollo 11 samples did not grow as well as plants grown in Apollo 12 and 17 samples. However, the researchers do have a conclusive explanation for this. For example, it appears that the plants with the most signs of stress were grown in soil more exposed to cosmic winds, which changed its composition. The presence of small iron particles in the soil can also cause additional stress to plants and hinder their development.

Vice versa

Conversely, the researchers suspect that growing plants may in turn alter the lunar soil. Although the specific mechanisms are as yet unknown. “The moon is a very, very dry place,” said researcher Stephen Elardo. “How will minerals in the lunar soil react when a plant grows on it, with the added water and nutrients? Will adding water make mineralogy more hospitable to plants?”

Follow-up research will build on these questions and more. But for now, the scientists are celebrating taking the first steps to grow plants on the moon. “We wanted to do this experiment because for years we’ve questioned whether crops can sprout on moon soil,” says Ferlo. “The answer, it turns out, is yes.”