Lettuce, Chinese cabbage, tomato, peas, radishes, wheat, rice, onion, garlic, and cucumber are all plants that have been grown (and partially eaten) in space. Today, we are talking about NASA’s Plant Habitat-04 project, which features growing spicy peppers in space.
Growing plants in space: the Plant Habitat-04 project
Providing food for astronauts is essential for long distance space travel in the future (the very near future?). While astronauts, who are currently living and working on the International Space Station (ISS), can rely on packaged food and fresh food delivered by supply missions from Earth, missions outside of the low-Earth orbit require an additional source of nourishment. Growing plants that allow harvesting fresh vegetables and fruits for missions that will take months or years is the only alternative for now.
NASA has been intensively researching the possibility to grow food crops on the ISS since 2015. But it’s not only about providing nutrition for astronauts. Taking care of plants helps with psychological well-being and fresh food increases variability and thus counteracts “getting tired” of the same food. Moreover, fresh food is higher in quality than packaged and stored food, which looses essential minerals and vitamins during storage.
The Plant Habitat-04 project launched in June 2021 and lasted for 137 days. This made it the longest plant experiment on the space station. It was also labeled as the most challenging experiment to date, because pepper plants take a long time to germinate and grow and they need pollination before growing fruit. After 109 and 137 days, astronauts could harvest the first peppers of the four plants grown in space. Now you might be wondering: why exactly would you grow peppers in space?
Peppers are rich in Vitamin C and Vitamin K, essential vitamins for us humans. Additionally, they provide taste. Astronauts often loose their sense of taste and smell while living in microgravity for a prolonged time. Spicy peppers could add some taste to the otherwise bland food.
The pepper cultivar grown in the small indoor growth chamber on the ISS was the “NuMex ‘Española Improved’ Pepper”. This was not a random choice, but scientist evaluated more than 20 different pepper varieties over a duration of two years. Pepper plants were grown on Earth in the “Advanced Plant Habitat”, the small indoor growth chamber in which plants are also grown on the ISS. Here, the NuMex ‘Española Improved’ Pepper performed the best. It adapted easily to the indoor controlled environment and grew better than its competitors. The NuMex ‘Española Improved’ Pepper is actually a hybrid of the ‘Hatch Sandia’ and the traditional ‘Española’ pepper of New Mexico and has been developed by the New Mexico State University.
How were peppers grown in space?
Let’s dive into the details of the Plant Habitat-04 project. Pepper plants were grown in the microwave sized “Advanced Plant Habitat” (APH) growth chamber. The chamber is equipped with 180 sensors and controls that allow full control over the environment of the plants, as well as monitoring how they grow and perform. This way, scientist on Earth can follow up the plant development and adapt the settings of the APH accordingly by changing for example light (intensity, duration, spectrum), temperature, or relative humidity. The project started with 48 pepper plants, but during the course of the experiment, astronauts cut back the number to four plants.
In the beginning, on Earth, pepper seeds were sterilized and placed in a science carrier that allowed transportation on a supply mission to the ISS. The science carrier fits into the APH. Interestingly, the plants were not grown in soil, as you might assume, but in the substrate arcillite. Arcillite is a granular calcined clay, which can hold a high amount of moisture, ideally for plant growth in microgravity. Peppers are self-pollinating, but there are no bees in space (luckily). This is why astronauts had to pollinate the pepper plants themselves, after they had formed flowers. This is merely easy: a common paintbrush is enough to take over the tasks of the bees. Next to the manual hand pollination, researchers run the fans inside the APH at different speeds, to create a gentle breeze that helped to transfer pollen. Needless to say: most pepper plants grew perfectly fine, flowered, and grew tiny spicy peppers after 109 days in space.
And how did they taste?
Many factors can affect the spiciness of a pepper. Growing in microgravity is stressful for the plants, which influences their spiciness. But also light, water availability, or temperature can influence their taste. Some peppers, that were grown on the ISS, were sent back to Earth to analyze the effect of microgravity on their flavor and texture. The others were eaten on the ISS. This created the famous picture of the first “space taco” with freshly harvested spicy peppers. According to the astronauts, the peppers were delicious.
The experiment was a huge success. However, many questions remain open. For example, astronauts noticed that peppers grown in space developed less fruit compared to plants grown on Earth. This might be an effect of the microgravity, however, much more research is necessary to understand its effect on plant growth and development.
Have a look at these incredible pictures:
All pictures belong to NASA
Yendler, B. (1998). Preliminary evaluation of soil moisture probe for use with arcillite. Advances in Space Research, 22(10), 1419-1423.