Scientists grow plants in soil samples collected from the Moon

They studied the soil samples for over a year, carefully monitored the growth and the genetic makeup of the plants grown in the samples, and came out with some fascinating results.  

Why the thale cress plant?

When we asked about the reason scientists chose thale cress specifically for their lunar soil experiment, Dr. Robert Ferl, distinguished professor at the Univerity of Florida and one of the authors of the study explained that the particular plant was chosen for some very important reasons. He told Interesting Engineering, “the first is that this Arabidopsis thaliana plant is extraordinarily well studied here on the Earth, there are probably thousands of laboratories around the world that work with or have worked with this plant so we know an awful lot about this plant from every nucleotide in its genome to what genes are expressed in salt.”

He further added, “the second reason is that it’s physically small, and it can grow in a small amount of material. We basically grew one plant in one gram sample now, one gram of lunar soil is about the same as a teaspoon full, so you can imagine to grow much of a plant, that plant would have to be small. The other thing that fits into this is that Arabidopsis is a big part of the last 20 years of space-related research. This plant’s been on the space station. It’s been on the space shuttle so not only do we have a bunch of terrestrial data to compare to, we also have a bunch of space-related data to compare to.”   

All the characteristics mentioned above of the thale cress plant made the researchers conclude that Arabidopsis, aka thale cress, would be the best plant to try in lunar soil for their experiments. During the experiment, thale cress was grown in both the volcanic ash and lunar soil samples.

How well did the plant grow in lunar soil?

Despite having a similar mineral composition, the lunar soil and volcanic ash samples supported the plant growth differently. Many lunar soil plants grew up with the same shape and color, but others were found to contain reddish-black pigments. These pigments depicts stress. Moreover, the plants grown in lunar soil experienced slow and stunted growth and expressed more stress genes than the plants grown in volcanic ash. 

Dark color plants that grew in lunar soil samples expressed more than 1,000 stress genes. The Apollo 11 plant expressed 465 genes, and the Apollo 17 and Apollo 12 samples expressed 113 and 265 stress genes, respectively. The stress in 71 percent of these genes was linked to the presence of metals, highly reactive O2 compounds, and salts. Interestingly, only the plants planted in the Apollo 12 and Apollo 17 samples managed to show growth. The Apollo 11 sample plant did not grow at all. 

The researcher explains that the samples were taken from different soil layers during the Apollo missions. The Apollo 11 soil sample remained in contact with the Moon's surface for a much longer time than the Apollo 12 and 17 samples. So perhaps the prolonged exposure to Moon's surface damaged the soil sample, and this is why the plant in Apollo 11 sample didn’t show any growth. 

At the end of their study, the researchers conclude that plants can be grown in lunar soil, but as compared to volcanic ash, the lunar soil samples do not support much plant growth, especially if they have been exposed to Moon’s surface. Since the lunar surface is often hit by solar wind and many types of cosmic rays which harm the soil, plant growth is better suited in lunar soil that has been less exposed to Moon’s external environment.   

The most important finding from the lunar soil experiment

The chemical composition and presence of metallic fragments also make lunar soil-less suitable for plant growth as compared to volcanic ash. However, the biggest takeaway from this experiment is still that scientists have somehow grown a plant in a soil sample taken from the Moon. 

Emphasizing the importance of this result co-author and geologist Stephen Elardo said, “from a geology standpoint, I look at this soil as being very very different from any soil you will find here on Earth. I think it’s amazing the plant still grows, right. It’s stressed, but it doesn’t die. It doesn’t fail to grow at all, it adapts.

The researchers also highlight that further research can enable us to know the ways plants can be efficiently grown on the Moon. Therefore, through related studies, we need to better understand how Earth plants interact with lunar soil.