If you were an astronaut living on the International Space Station (ISS) or traveling far into space for months or years, you'd need fresh food. You'd need to grow crops. You'd need agriculture in space.

But can plants grow in space? How difficult is it to create a sustainable food source up there? Let's explore how far space-based farming has come and what the future of food in space might look like.

Space-Based Farming Is Complicated

One of the biggest challenges of agriculture in space is finding water and nutrients on other planets or transporting them in a spacecraft or space station. On a planet like Mars, for example, locating water or nutrients so plants can grow in space might be near impossible, and hauling a shipment of water or nutrients to the ISS is expensive. Launching a single pound of cargo into space costs about $10,000, and 1 gallon of water is about 8.33 pounds — so it'd be a pretty hefty price to send enough H₂O for crops into space.

The astronauts who live on the ISS receive regular shipments of food that sometimes include fresh fruits and vegetables, but they usually have to add water to dehydrated food. For a multi-year journey to another planet, there wouldn't be any resupply shipments. Over time, prepackaged freeze-dried meals would get old and seem less tasty, and the vitamins in them would likely break down.

This poses major problems for astronaut health, which explains why it's mandatory to figure out not only how can plants grow in space but also how to send autonomous food-growing systems to places like Mars so they'll be there and ready to go when people arrive.

Another big challenge that humans growing crops off-world must face is finding a decent place to farm the plants. Rocky places, like the moon and Mars, don't have soil. The ground there is regolith — loose, gravelly material that doesn't have organic materials in it like the soil on Earth does.

Engineers Have Found Creative Ways to Farm in Space

Nevertheless, NASA has been growing plants in space without soil or water since 1997. On the Mir space station, astronauts raised adzuki beans, a high-protein food crop. They started the beans from both cuttings and seeds and suspended them in midair in a growing chamber. Astronauts aboard the space shuttle and the ISS performed experiments using the principles of aeroponics to find a solution: Can plants grow in space using an air and mist environment?

They discovered that they could successfully grow food without any soil and with only small amounts of water. In the aeroponic systems, the roots of the plants developed in an enclosed environment and were misted with a nutrient-rich spray. Using the aeroponic systems reduced water use by 98%, fertilizer use by 60% and pesticide use by 100%.

Another benefit of these crops is that they can be planted and harvested year-round without interruption. Aeroponically grown plants also take up more minerals and vitamins than regular soil-based plants, which means they're healthier and potentially more nutritious. And remember: Nutrition is crucial for crews who need to grow their own food during long-term missions in deep space.

Getting Hungry?

At this point, you're probably wondering what types of plants could be grown off-world. In the 1950s and 1960s, early research into space agriculture focused mostly on algae, which admittedly doesn't sound very tasty. But by the 1980s, crop lists included wheat, soybeans, potatoes, rice, sweet potatoes, lettuce and peanuts.

More recently, engineers have focused their efforts on designing a ""salad machine"" system that could provide fresh food to astronauts on space stations and even on long-duration transits to Mars.

Introducing the Space Salad

Astronauts have had considerable success with growing and eating vegetables on the ISS, starting with red romaine lettuce. The current garden on the space station is called Veggie, short for Vegetable Production System. It's a simple, low-power system that grows fresh and nutritious pick-and-eat salad crops.

Veggie is about the size of a carry-on suitcase and can hold six plants. Each plant grows in a ""pillow"" filled with a clay-based growth media and fertilizer that helps distribute water, nutrients and air in a healthy balance around the roots. Without the pillows, the roots would either drown in water or be engulfed by air because of the way fluids in space tend to form bubbles.

Astronauts have been using Veggie to grow three types of lettuce, Chinese cabbage, mizuna mustard, red Russian kale and zinnia flowers. The Veggie team also developed a produce-sanitizing citric acid-based wipe to clean the leafy greens since there isn't a way to cook them in space yet. Astronauts aren't able to sprinkle salt and pepper on their veggies because it would float away and could clog air vents or contaminate equipment, so they use liquid seasoning on their food instead.

Since green plants reflect green light and absorb red and blue wavelengths, light emitting diodes (LEDs) above the plants glow magenta and produce the spectrum of light most suited to the plants' growth. Crew members tend to the plants by opening wicks to help seedlings emerge, providing water, thinning the seedlings and monitoring health and progress, which includes taking photos to send to the ground team. Half of the crop is frozen and returned to Earth for analysis, and the other half is weighed and eaten by the crew.

Peas and Quiet

Crew members on the ISS also assess how much they enjoy interacting with the Veggie system and how it affects their mood. It turns out that eating the same food over and over gets boring. So boring, in fact, that NASA has been studying food acceptability and menu fatigue, which looks at whether or not crew members like a food enough to actually eat it. Food acceptability affects caloric intake and nutrition.

Researchers discovered, however, that taking care of plants in space enhanced the astronauts' happiness and well-being. This finding correlates with a number of scientific studies on the effects of gardening, sometimes called horticultural therapy. The studies have linked gardening with a wide range of health outcomes, including reductions in depression, anxiety and body mass index as well as increases in life satisfaction, quality of life and sense of community. Results of another study showed that gardening increased life satisfaction, vigor, psychological well-being and cognitive function. Apparently, gardening is fun and relaxing no matter where you do it.

Astronauts also found that growing fresh flowers in space created a beautiful atmosphere and allowed them to enjoy a piece of home. Flowers were especially popular with astronaut Scott Kelly, who photographed a bouquet floating in the cupola against the backdrop of Earth.

The Future of Agriculture in Space

If we want to expand our ability to explore places farther from Earth than the ISS, then figuring out space agriculture is necessary. Travelers who venture far into space could be gone for months or years without resupply shipments, and multivitamins alone will not be enough to keep astronauts healthy as they explore deep space. NASA engineers have been partnering with leading agri-biology companies to understand more about the types of plants that can be grown off-world.

One new concept developed by the teams at NASA is the next-generation inflatable growing chamber called the Flex Aeroponic System. It's lightweight and flexible and can be packed up and stored during transportation. Once the garden is opened up on another planet, seeds can be placed on specially designed mesh holders inside the chamber.

Researchers found that plants exposed to the effects of microgravity could produce greater yields than in field settings here on Earth — as much as 1,000 bunches of lettuce, herbs and vegetables in less than 25 days. This type of high-performance rapid crop production of pesticide-free herbs, grains, tomatoes, lettuce, peppers and other vegetables has great potential for integration into future moon and Mars missions.

This could ultimately lead to new strategies for growing and maintaining healthy food plants on long-term space flights and for future bases on other planets and moons. Space agriculture even has the potential for helping us learn more about how to best grow food here on Earth.

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