As NASA plans long-duration missions to the Moon and Mars, a key challenge is figuring out how to feed crews during their weeks, months, and even years in space.
Food for crews aboard the International Space Station is primarily prepackaged, requires regular resupply deliveries aboard cargo spacecraft, and degrades in quality and nutrition. But what if astronauts could grow some of their own food in microgravity? Researchers are exploring the idea by testing various crops and equipment to figure out how to do this without a lot of extra hardware or power.
To date, NASA has grown a variety of plants, including lettuces, tomatoes, and radishes – and learned a lot about how to successfully do so in the process.
Picking the right plants
The first step in this research is identifying which plants to test. NASA started a project in 2015 with the Fairchild Botanical Garden in Miami called “Growing Beyond Earth.” The program has recruited hundreds of middle and high school science classes across the U.S. to grow different seeds in a habitat similar to one on the space station. These student citizen scientists are helping NASA develop technologies for growing food crops for future long-duration missions.
Gardens in space
NASA also has tested facilities to host future microgravity gardens. One is the Vegetable Production System, or “Veggie,” a simple, low-power chamber that can hold six plants. Seeds are grown in small fabric “pillows” that crew members look after and water by hand, much like caring for a window garden on Earth. The Passive Orbital Nutrient Delivery System, or Veggie PONDS, works with the Veggie platform but replaces the seed pillows with a holder that contains a small reservoir of water for the plant.
The Advanced Plant Habitat is a fully-automated facility designed to study growing plants in ways that require only minimal crew attention.
The right light and food
The type of light can affect plant size, nutritional content, microbial growth, and taste. Plants particularly rely on red and blue light to grow. Experiments aboard the space station showed that plants in space grow well under the same light conditions preferred by those on Earth. While green lights are not necessary for plant growth, they are included in plant growth systems so that the plants look like those grown on Earth.
The Veg-04A, Veg-04B experiments grew Mizuna mustard, a leafy green crop, and Veg-05 grew tomatoes. The experiments grew the crops under different light conditions and compared plant yield, nutritional composition, and microbial levels to ones grown on Earth. Crew members also rated the flavor, texture, and other characteristics of the two mizuna experiments.
Plant Habitat-04 analyzed plant-microbe interactions and assessed the flavor and texture of chile peppers. Crew members ate peppers from the first crop, harvested on Oct. 29, 2021, and from the second harvest. Twelve peppers from the second harvest returned to Earth for analysis as well. This experiment demonstrated that research about space crop production is on the right path and researchers plan to apply lessons learned to testing other plants.
The influence of gravity
Gravity affects how plants grow and the yield of crops. An early experiment, PESTO, found that microgravity alters leaf development, plant cells, and the chloroplasts used in photosynthesis, but did not harm the plants overall. In fact, wheat plants grew 10% taller compared to those on Earth.
The Seedling Growth investigations showed that seedlings can acclimate to microgravity by modulating expression of some genes related to the stressors of space, a discovery that adds to knowledge about how microgravity affects plant physiology.[1]
One way that plants sense gravity is via changes to calcium within their cells. Plant Gravity Sensing, a JAXA (Japan Aerospace Exploration Agency) investigation, measured how microgravity affects calcium levels, which could help scientists design better ways to grow food in space.
ADVASC, an investigation that grew two generations of mustard plants using the Advanced Astroculture chamber, showed that seeds were smaller but germination rates near normal in microgravity.[2]
Water delivery
One significant challenge for growing plants in microgravity is providing enough water to keep them healthy without drowning them in too much water. Plant Water Management demonstrated a hydroponic (water-based) method for providing water and air to plant roots. The XROOTS study tested using both hydroponic and aeroponic (air-based) techniques to grow plants rather than traditional soil. These techniques could enable large-scale crop production for future space exploration.
Transplanting veggies
During the VEG-03 investigation, which cultivated a variety of plants including Extra Dwarf Pak Choi, Outredgeous lettuce, and Dragoon lettuce, NASA astronaut Mike Hopkins noticed some of the plants were struggling. Hopkins conducted the first plant transplant in space, moving extra sprouts from thriving plant pillows into two of the struggling pillows in Veggie. The transplants survived and grew, opening new possibilities for future plant growth.
Plant genetics
Plants exposed to spaceflight undergo changes that involve the addition of extra information to their DNA, affecting how genes turn on or off without changing the sequence of the DNA itself. This process is known as epigenetic change. Plant Habitat-03 assesses whether such adaptations in one generation of plants grown in space can transfer to the next generation.
The long-term goal is to understand how epigenetics contribute to adaptive strategies that plants use in space and, ultimately, develop plants better suited for providing food and other services on future missions. Results also could support the development of strategies for adapting crops and other economically important plants for growth in marginal and reclaimed habitats on Earth.
The human effect
Gardens need tending, of course. The Veg-04A, Veg-04B, and Veg-05 investigations also looked at how tending plants contributed to the well-being of astronauts. Many astronauts reported they found caring for plants an enjoyable and relaxing activity – another important contribution to future long-duration missions.
Astronauts report that the time spent gardening makes them excited to eat the fresh produce once it is ready. That encourages them to creatively use the produce as ingredients in their meals, increasing their quality of life in space and boosting their morale.
The Biological and Physical Sciences (BPS) Division of NASA’s Science Mission Directorate at NASA Headquarters in Washington provides funding for Veggie, the APH, and related investigations.
Search this database of scientific experiments to learn more about those mentioned above. Space Station Research Explorer
Citations:
1 Medina F, Manzano A, Herranz R, Kiss JZ. Red Light Enhances Plant Adaptation to Spaceflight and Mars g-Levels. Life. 2022, 12(10), 1484; https://doi.org/10.3390/life12101484
2 Link BM, Busse JS, Stankovic B. Seed-to-Seed-to-Seed Growth and Development of Arabidopsis in Microgravity. Astrobiology. 2014 October; 14(10): 866-875. DOI: 10.1089/ast.2014.1184.PMID: 25317938
