Humans in space have to eat. In the early days of space exploration, they got to eat paste and drink Tang (or so the legends tell us). That’s hardly a great long-term diet. Plants should be in there, too. And, astronauts aboard the ISS have been growing gardens in space for years.
So, what else do we need to know about farming in space? Well, as it turns out, quite a bit. That’s why NASA is sending up a plant habitat to the ISS. It’s part of a program called Epigenetic Adaptation to the Spaceflight Environment—Accumulated Genomic Change Induced by Generations in Space (Plant Habitat-03). The idea is to follow successive generations of plants as they germinate, grow, live, and die in a microgravity environment. This experiment will fly to the ISS on the Northrup Grumman Commercial Resupply Services Mission 18, tentatively set for November 6th, 2022.
Growing up Green in Low Gravity
While low gravity might seem like a pretty relaxing place to live and work, for plants, it’s actually stressful. Like humans, plants evolved in Earth’s gravity and in ground-based environments. Exposure to the stress of spaceflight shows that things like an arabidopsis plant (previously grown on the station) actually change their genetics. It’s not a mutation like we see in SF movies. It’s more like the plant adds a little extra something to its DNA to affect gene expression. That’s the process where a gene is stimulated or turned on in a cell to make RNA and other proteins. Living in space changes that a little bit, but figuring out that process and how extensive it is takes time and multiple experiments. That’s where Plant Habitat-03 comes in.
“Plant Habitat-03 will provide a better understanding of how the epigenome contributes to an organism’s ability to adapt to environmental stress, in both current and subsequent generations,” said Sharmila Bhattacharya, space biology program scientist in NASA’s Biological and Physical Sciences Division at NASA Headquarters in Washington. “This is an important insight into how astronauts could potentially grow repeated generations of crops in orbit as well as on the Moon or Mars to provide food and other services aboard future space missions. The results can also support the development of strategies for adapting crops for growth in extreme environments on Earth.”
Plants Adapting in Space
Plants evolve all the time. We see it on Earth, where farmers and researchers genetically modify them. In nature, the same processes take thousands of years. Plant Habitat-3 will put them in microgravity and then watch them adapt to life in space. What epigenetic changes (that is, changes in gene expression) will occur? Will they be transmitted to subsequent generations? Or, will each set have to “re-learn” all over again in new generations? Those are the questions the research team wants to answer. So, what’s the experimental process?
As part of the project, the experiment will grow seeds in a special unit aboard the ISS. Once the plants reach maturity, astronauts will pick them and return the harvested plants back to Earth. Their seeds will return to space, along with new seeds on their first “mission” to the ISS. Ultimately, the idea is to find out just how much the plant epigenetics change from spaceflight-affected specimens and compare them to new generations of plants flown in space.
Arabidopsis plants imaged in white light (left) and Green Fluorescent Protein (GFP) excitation illumination, right. The arabidopsis are also part of the Plant Habitat-03 experiment. Image provided by Anna-Lisa Paul, Ph.D. and Robert Ferl, Ph.D., Department of Horticultural Sciences, University of Florida.
Plant Habitat-03 is one of many projects that study how living things respond to living in space. Previous ISS studies have looked at growing plants in space, for example, by studying how best to provide water and aeration to microgravity gardens. Human studies are, of course, well known. However, if we’re going to put people into space for long periods of time, understanding their space-borne food sources is important, too. Clearly, as NASA prepares for future human exploration, including the ambitious Artemis missions, having a good understanding of the food those people will need is a huge part of the effort.
Studies in Space Benefit Earth
In addition to the space-based applications of the Plant Habitat-03 flight, there are Earth-based benefits. For one thing, our planet has regions that are undergoing stresses from climate change. Finding out how stress affects genetic expression in food crops could help farmers on Earth to adapt crops as conditions change across the continents.