Scientists have grown seeds in moon soil for the first time, using samples recovered during NASA missions in 1969 and 1972, in an accomplishment that heralds the promise of using earthly plants to support human outposts on other worlds.
On May 12, the researchers planted seeds of Arabidopsis thaliana, a small flowering weed, in 12 small thimble-sized containers, each containing a gramme of lunar regolith, and watched them sprout and grow. Because lunar regolith differs greatly from Earth soil in terms of sharp particles and lack of organic material, it was unknown whether seeds would germinate.
"It took our breath away when we first saw that abundance of green sprouts cast over all of the samples," said horticultural sciences professor Anna-Lisa Paul, director of the University of Florida Interdisciplinary Center for Biotechnology Research and co-leader of the study published in the journal Communications Biology.
"Plants can thrive in the lunar regolith. That one simple statement is significant because it opens the door to future exploration using resources already on the moon and, most likely, Mars " Paul stated.
Every seed germinated, and there were no visible differences in the early stages of growth between seeds sown in the regolith, which was mostly crushed basalt rocks, and seeds sown in volcanic ash from Earth, which had a similar mineral composition and particle size.
Unsurprisingly, the regolith seeds performed worse than the comparison plants. They grew slower and smaller in general, had more stunted roots, and were more likely to exhibit stress-related characteristics such as smaller leaves and deep reddish-black coloration that is not typical of healthy growth. They also displayed stress-related gene activity, similar to plant reactions to salt, metal, and oxidation.
"Plants could grow in the regolith, but they had to work hard metabolically to do so," Paul explained.
The fact that they grew at all was remarkable to the researchers. Rob Ferl, a University of Florida assistant vice president for research and co-leader of the study, expressed "joy at watching life do something that had never been done before."
"Seeing plants grow is an accomplishment because it implies that we can go to the moon and grow our food, clean our air, and recycle our water using plants in the same way that we use them on Earth. It is also a revelation in the sense that it asserts that terrestrial life is not limited to Earth” Ferl continued.
Arabidopsis, also known as thale cress, is widely used in scientific research, including previous experiments in space, due to its rapid life cycle and a thorough understanding of its genetics.
NASA made 12 grammes (a few teaspoons) of regolith collected during the Apollo 11, Apollo 12, and Apollo 17 missions available. The researchers planted three or four seeds in a dozen containers that had been moistened with a nutrient solution, then placed them in a laboratory at about 73 degrees Fahrenheit (23 degrees Celsius) under pink LED lights.
Within three days, the seeds sprouted. The researchers removed all but one plant from each container after about a week of growth. The one was allowed to grow for 20 days before its leaves were harvested to assess gene activity.
The researchers also discovered that regolith exposed to cosmic rays and solar wind on the lunar surface for a longer period of time was less hospitable to growth.
Earth plants could aid in the establishment of outposts on the moon and Mars, as depicted in the 2015 film 'The Martian,' in which an astronaut grows potatoes on the Red Planet. The Artemis programme at NASA envisions humans returning to the moon's surface in the coming years. "Plants are deeply embedded in the science of space exploration because of their life-support role," Ferl explained.
