Space botanists are working on strategies to grow crops on the lunar surface, as NASA makes strides toward sending astronauts to the Moon through the Artemis program. A team of scientists at the University of Florida successfully grew small plants in lunar soil brought back during three different Apollo missions. How did they do it, and what does it mean for the future of space exploration? Dr. Anna-Lisa Paul explains.
Jim Green: Can we grow food on the Moon? This may end up being a fundamental question of survival in space. Let’s talk to a space botanist.
Anna-Lisa Paul The only way that humans can be explorers is if we take our plants with us.
Jim Green: Hi, I’m Jim Green, and this Gravity Assist, NASA’s interplanetary talk show. We’re going to explore the inside workings of NASA and meet fascinating people who make space missions happen.
Jim Green: I’m here with Dr. Anna-Lisa Paul. And she is the professor of horticultural sciences at the University of Florida’s Institute for Food and Agricultural Sciences. And she is the director of the University of Florida’s Interdisciplinary Center for Biotechnological Research.
Jim Green: Dr. Paul and her colleagues just published a fantastic new study. And this study describes how plants grow in samples of lunar soil brought back by astronauts in the Apollo program. Wow! I can’t wait to hear how this was pulled off. So welcome Anna-Lisa to Gravity Assist.
Anna-Lisa Paul: Thank you. Thank you very much. Pleasure to be here.
Jim Green: The paper that’s out now is really exciting, because it tells us that we now have options of going to the Moon and being able to live and work on a planetary surface for long periods of time, because we have an aspect of sustainability by growing food. So is this project something you’ve been wanting to do for a long time?
Anna-Lisa Paul: Absolutely. This is a project that has been sort of on my, and my colleague, Rob Ferl’s radar, for decades, because when you think about if the only way that we can humans can be explorers, is if we take our plants with us. Plants are what allows us to be explorers, they can go past the limits of a picnic basket. So for us who work in space biology, we wanted to know if when we get to a new surface, can we use the resources that are already existing there, the in situ resources? And for the Moon, that would be the regolith, which can be used as the dirt to grow plants.
Jim Green: Well, how hard was it to get your hands on these samples, the original samples from the Apollo program?
Anna-Lisa Paul: It was pretty hard to get those. You have to remember, they’re a national treasure, they are completely irreplaceable in their original form. And so when you have a couple of biologists who go to an institution of higher archiving from NASA of the original Apollo samples, and you say, “Yes, we’d please like to have some of your precious materials and get them all messy and grow plants in them!” They say, “Excuse me, you want to do what?” And so it took three different iterations of proposals, which also include a ton of background information and tests with lunar simulants before we could convince the powers that be that, yes, yes, we will take good care of them. We’re good representatives of what science can be done, and they let us have some. In fact, they let us have 12 grams.
Jim Green: 12 grams. I know that doesn’t sound a lot.
Jim Green: Well, what’s really amazing to me when we think about plants growing in regolith is, is what regolith is. You know, it’s really ground up rock, that comes from impacts over and over, billions of years of impacts on the Moon, blasting everything apart. And when you look at the regolith, this ground-up rock, in a microscope, it’s got all these shards. It’s, it’s very sharp, which is one of the reasons why we’re worried about this regolith, when humans walk around in spacesuits, getting into their lungs.
Jim Green: And so the concept that we can actually grow plants in it, was really amazing. So, tell us about these lunar samples. Did they come from one location or many locations?
Anna-Lisa Paul: So the samples actually came from three locations: from Apollo 11, Apollo 12, and Apollo 17. And so the three sites that the astronauts worked on had different characteristics. All of the materials are what are called basaltic. And so most of them were sort of ground up basalt, lava kind of, kind of materials. But each of the sites were exposed to the surface for different periods of time. And what that means is that the regolith has what’s called different levels of maturity.
Anna-Lisa Paul And so the regolith from the Apollo 11 site, for instance, was more mature. That means it has been exposed to the cosmic wind for longer. So the particles are smaller, the edges are sharper. The Apollo 17 samples were particularly interesting in that it, the type we got was actually a compendium of materials from all over the site, because it was the dirt, if you will, that got caught underneath a bumper on the lunar rover.
Anna-Lisa Paul: And as, as they were leaving, Harrison Schmidt said, wow, there’s a whole bunch of stuff here. Let’s not let that go to waste. And he dumped it all into a bag and it came back to Earth for, for us eventually.
Jim Green: Wow, that’s fantastic. So tell me about the experiment. If you only had a little bit from each of these sites, how are you going to really grow plants in them?
Anna-Lisa Paul: So we used the plant called Arabidopsis thaliana. And the cool thing about Arabidopsis is, in addition to being very well characterized at the genomic level, and gene level, it’s small, it’s really small, and you can actually grow an almost full size plant in a single gram of material.
Jim Green: Wow.
Anna-Lisa Paul: So what we did is we had these specialized plates that are normally used for cell culture, there are only about 12 millimeters across — each one of these little pots, if you will. And we put the regolith inside these little pots and then planted seeds on top of them, watered them from below and: instant lunar garden.
Jim Green: Wow, that’s unbelievable. So you had a regimen of just adding water to the to the seed and that’s all it took?
Anna-Lisa Paul: It took a little bit of nutrients, too.
Jim Green: Okay.
Anna-Lisa Paul: And so how it was set up was a little plug of material called rockwool, which is essentially just spun lava rocks, that makes a sponge, and then the regolith goes on top of that little sponge. And so now the sponge acts as a capillary wick to get liquids up into the regolith. So the nutrient solution that went down into the base of the tray got wicked up into the regolith, and it was essentially watered from below.
Jim Green: Wow, interesting. So then it’s easy to think about how that could work by developing a greenhouse with these kind of attributes on the Moon and then just bringing in the regolith.
Jim Green: So at the end of the experiment, did you then take apart the regolith to see how the roots grew with in the planter?
Anna-Lisa Paul: We did. Because we planted more than just a single seed at first, when we thinned the little tiny seedlings away to just leave a single plant in each one of those little micro pots, we also got to look at the roots there. And so we could see that the plants that were growing in the simulant, it’s called this JSC-1A, it’s a type of volcanic ash that’s mined on Earth, that’s what we use as our control.
Anna-Lisa Paul: Compared to the lunar regolith, the JSC-1 simulants were nice and long and tapered and looked very healthy, but the roots that were growing in the regolith were kind of scrunched up and they weren’t quite as healthy looking. Nonetheless, once they grew, you could get decent looking plants growing in the regolith. And just to look at them with your eye, they’d look a little smaller than the ones in the controls. But the real key was when you ground them up, and you look at what genes are being expressed.
Jim Green: Now, as you said, you use simulant, which means we think we’ve been able to develop a process that can make lunar-like regolith without bringing it from the Moon. But as you said, already, there’s some differences between that simulant and what the real regolith looks like. But that’s an important control factor. That also helps us figure out if we’re making those simulants correctly or not.
Anna-Lisa Paul: Yup.
Jim Green: So what did you find out?
Anna-Lisa Paul: So when you take a look at the controls, I have to say, any experiment is only as good as your control, right?
Jim Green: Right.
Anna-Lisa Paul: And so, the control material really did look a lot like the lunar regolith. It behaved a lot like the lunar regolith in the way it absorbed water and the way that it kind of just settled into the pots and everything. But when we’ve looked at the example of even if you take two plants that looked very similar between the control and the lunar regolith grown, we found that the kind of genes that the plants expressed different from the ones that were in the control were mostly genes that are associated with metal stress, like heavy metals, or salts, or what we call oxidative stress.
Jim Green: Oooh!
Anna-Lisa Paul: Even though those materials per se weren’t necessarily in those regoliths. It’s not like the regoliths were actually salty. But the plants perceived the type of stress they were seeing in that material as salt stress, as metal stress. And so that was an interesting insight that they were changing the way they express their genes to adapt to that new and novel environment.
Jim Green: Oooh. So this is really critical to understand. Because once you understand that, there may be processes and procedures that you could do that alleviate that plant stress that allows them on, on the real example, on the Moon in a greenhouse, to then really flourish better than even what you did in the laboratory.
Anna-Lisa Paul: That’s exactly right. That’s button on. So the Arabidopsis is really closely related to some of your favorite vegetables, like, say, broccoli. And we know that if we want our broccoli plants or kale plants to be healthy and growing in the lunar regolith, in a greenhouse, we know that we’ll have to mitigate some of these kind of stress responses. We can do that in two ways. You can engineer their environment by mitigating perhaps some of the materials that are in the regolith, you can also engineer the plants themselves. And you can make them less sensitive to some of these aspects. And so instead of putting their energy into the stress response, they put that energy into making more broccoli.
Jim Green: Right! That’s really a, just a huge advance. By doing this on the Moon, we’re going to also learn the processes and procedures we’ll have to do on Mars. So that will be really critical. S o I really dearly love this idea. So if I was in the lab, and we were done with the experiment, we were taking them apart and looking at the roots, I might be tempted to eat one of these. Did anyone do that?
Anna-Lisa Paul: Well, we didn’t eat any of those because, think about it: they’re a very small and very precious resource that we wanted to save to do the biochemical analyses. You could eat Arabidopsis. People have eaten them before, but it’s not exactly something that would be good in a salad.
Jim Green: (laughs) So not so tasty after all.
Jim Green: I can imagine walking into the lab, when it, when you had started these plants growing. And the first time you realized this was gonna work. What was that like?
Anna-Lisa Paul: Oh, so the preparation that went into this experiment is extraordinary. All the background, all the setup, everything, the way we planted them, every aspect of it was complex. And so then at the end, Rob, and I walk out to our secure growth chamber where these things are going to go, we set them all up under their pink LED lighting systems that will keep them going. And we closed the door and we thought, all right, three days, things should be germinating in three days. Well, two days later, we walked back in there just to kind of check, and we’re looking down at all those plates. And every single one had germinating seeds in it.
Jim Green: Wow!
Anna-Lisa Paul: The controls, the lunar samples, everything was germinating. There’s this tiny nascent greenness, every single one, and it just took our breath away. It worked. It really worked. How cool is that?
Jim Green: You know, it reminds me of the theme in the movie “The Martian,” where Mark Watney goes over to his potato plant that is now growing for the very first time, touches the leaf, and says “hello.”
Anna-Lisa Paul: Yes, exactly.
Jim Green: Wow, that’s great. I can also imagine that this will enable you to think of the next best experiment to do. Have you been thinking about and formulating your next steps?
Anna-Lisa Paul: Oh, absolutely. One of the things that would be wonderful to do is to have additional replicates for this. With four grams each from each site, we could obviously only have four replicates of one individual plant each. Being able to have a larger volume of material so that we could try different kinds of mitigations. All of the samples had to be treated with the same nutrient solution for instance. And so if we had enough material, we could also change the variables of what kind of nutrients we did. Are there other ways to mitigate some of the effects of the regolith? Those are the kinds of things you can only do with more material.
Jim Green: I understand you’ve done some field tests in far off places here on Earth.
Anna-Lisa Paul: Yeah, so I’ve definitely had the privilege to explore some very interesting, what we call analog sites, in the in the world. The first step was, Rob Ferl and I went to the far north Canadian Arctic at an old impact site, called the Haughton Crater on Devon Island. And one of the reasons we went to Devon Island was to practice utilizing in situ resources in a greenhouse that was growing there.
Anna-Lisa Paul: And so we collected these, what we call, brecciated materials from this old impact crater, which was 20-plus miles across, that was very lunar looking. And we’ve use some of those materials in the greenhouse. We also used the JSC-1 simulant in the greenhouse, along with other kinds of materials and asked: Can we populate a greenhouse substrate with these kinds of non-traditional growth substrates to create materials and crops over the winter?
Jim Green: So what did you find out when you did that?
Anna-Lisa Paul: Well, we find that they actually like growing in the JSC-1 simulant a little better than they liked growing in the brecciated materials we dug out of the crater. (laughs) And part of that is because a lot of the materials have different types of chemicals in them that are actually in some ways more analogous to what it would be on Mars. Whereas the lunar regolith is pretty much just devoid of everything, the Martian regolith i, looks to be, although nobody’s brought any back, it looks to be high in, say, perchlorates and other kinds of reactive chemicals that would have to be, again, ameliorated before you could grow plants in it. But you’d be have to be able to use the materials from where you land.
Jim Green: So on the Moon, I imagine we’re going to have a greenhouse, but can we really grow these out in the vacuum of space?
Anna-Lisa Paul: Well, they would have to have a greenhouse just like a human would have to have a greenhouse because that there’s no atmosphere on the surface of the Moon. So all of the plant growth would be being carried on in some kind of greenhouse or other sort of enclosed habitat along with its attending humans.
Jim Green: Well, you know, another part about that, that I like, is the fact that these plants as they grow will smell wonderful. And you get not only this the green of the plant, you also get the smells, and it’s gotta remind astronauts of home.
Anna-Lisa Paul: That that is so true. And I have actually a personal experience that, that speaks to that very well. I mentioned the work that I’ve done in the high Canadian Arctic. Well, I’ve also been down in Antarctica for a while. And again, working on a greenhouse that was essentially called the Future Exploration Greenhouse, part of the Eden ISS project, that was an analogue of what you might find on the Moon or Mars.
Anna-Lisa Paul: I was down there for several days, and the weather was just horrible, and nobody could go outside, it was absolutely impossible, and everything was dark, and bleak and awful. And then, when the weather started to clear just a little bit, we went out to the greenhouse for the first time on that trip and walked into the door, and you’re met by the smells and the moisture and the greenness. And it was like, all of the stress evaporated from all of us. And we were home for a bit. And I can well imagine it would be like that for an astronaut. And you can’t underestimate how powerful, how powerful a plant can be from that context, as well as the fact that it cleans your air and gives you clean water and gives you food. It also gives you something spiritual.
Jim Green: Very nice.
Jim Green: Well, Anna-Lisa, I always like to ask my guests to tell me what that person place or event was that got them so excited about being in the sciences that they are today. And I call that event, a gravity assist. So Anna-Lisa, what was your gravity assist?
Anna-Lisa Paul: Well, gravity assist for me has been people, and the very first person was my mom. And I can remember quite keenly as a little kid asking my mother about how something worked. And she would say, “I don’t know, let’s find out.” And so it was always this, this journey of discovery. I would be given science books as a small kid, even though I couldn’t quite read them at that level. And we’d go through as a family trying to figure out how to do the kind of experiments we could do in the backyard. And I got really interested in plants, because plants were the only things that were taking the energy that comes into the planet, and turning it into stuff that we needed.
Anna-Lisa Paul: So as I got older and started wondering about how plants work, it kept taking me one step after another until I decided I’d like to understand how plants respond to novel environments, and the most novel environment out there is space.
Jim Green: Wow, fantastic. That, that’s a wonderful environment to be in, where you can work with your parents on a journey of discovery, and then realize how you can make a wonderful career out of it. So thanks so much for telling us about this really fundamental and exciting research.
Anna-Lisa Paul: I’m pretty lucky. Thanks.
Jim Green: You’re very, very welcome. Well, next time, we’re going to talk to a researcher at the Kennedy Space Center, who also works on growing plants in space. But in this case, it’s all about astronauts growing them on the space station. You won’t want to miss that. I’m Jim Green, and this is your Gravity Assist.
Lead producer: Elizabeth Landau
Audio engineer: Manny CooperLast Updated: May 13, 2022Editor: Gary Daines