NASA's Space Lettuce Is Safe and Nutritious, Paving Way for Crops on the Moon and Mars

The lettuce grown on board the International Space Station between 2014 and 2016 was just as safe and nutritious as crops cultivated on Earth, scientists have found. The finding will help pave the way for vegetables to be grown during longer missions to the moon, Mars and beyond, researchers say.

Red romaine lettuce seeds were sent to the ISS as part of an experiment to see if cultivation in space was possible. Astronauts grew and ate the lettuce as part of the Vegetable Production System experiment, dubbed "Veggie" for short.

"[Astronauts] posted photos of lobster salad lettuce wraps that they made and we heard that they ate the lettuce on cheeseburgers and tacos they made out of items available," NASA's Christina Khodadad and Gioia Massa, from the Kennedy Space Center, told Newsweek in an email.

Khodadad and Massa are authors of a study that examined the microbiological and nutritional quality of the lettuce after its stint on the ISS. Samples of the lettuce were frozen and sent back to Earth, where researchers conducted experiments to test the lettuce for any differences. As a control, the team also grew the crop in the same conditions on Earth. The plants were cultivated in chambers with LED lighting and a watering system. Findings were published in the journal Frontiers in Plant Science.

Most of the food eaten by astronauts on the ISS is processed and pre-packaged. Over time, however, this stored food starts to lose quality and nutrition. While this is not an issue for astronauts on board, as food from Earth is supplied regularly, for long-duration spaceflight—like those to the moon and Mars, which NASA is currently planning—the issue of nutrition could become a problem. A manned mission to Mars, for example, may involve food being sent ahead, long before astronauts arrive.

"Right now we cannot guarantee that we will have a diet to meet the needs of the crew for these longer, deep space missions, so one potential solution will be to supplement the packaged diet with fresh produce," Khodadad and Massa said. "This [space-grown lettuce] will provide additional vitamins and other nutrients, flavors, textures and variety to the packaged diet. Growing plants may also help with menu fatigue and provide psychological benefits when astronauts are far from home. In the long term, if we ever want to have space colonization, growth of crops will be crucial for establishing any level of sustainability and self-sufficiency.

"In addition to providing food, plants may also play a role in future Life Support Systems needed for long-duration missions. Plants generate oxygen as well as remove and fix carbon dioxide, which is critical in closed systems like the ISS or future moon/Mars facilities."

Analysis of the lettuce grown on the ISS showed it was comparable to the plants grown on Earth. Its nutritional value was largely the same, as were the microbial communities. They also found that none of the types of bacteria were those known to cause disease in humans, like E. coli and Salmonella.

space lettuce
Lettuce grown on the ISS. Researchers have found the crop was as nutritious and safe as a control group grown on Earth. NASA

The biggest issues for growing crops in space, the researchers said, is delivering water, oxygen and nutrients to the roots. "In microgravity you have no natural convection, and water and air do not mix well," they explained. "Plant roots need both water and oxygen, and getting the correct levels is very tricky. Doing this in a sustainable, reusable approach using low power, mass, volume, and crew labor is even harder."

However, they said that with the right plant growth systems, lettuce and other crops can be grown anywhere. This includes the moon and Mars. Khodadad and Massa said there is another Veggie chamber on the ISS now, and astronauts on board are growing and testing different crops. Samples are being sent back to Earth for analysis.

"Understanding how growing different varieties affects this ecosystem is very important," Khodadad and Massa said. "We continue to study changes that take place over time to see the dynamics of the microbial community structure. We also are continuing to test other crops, with the addition of small fruiting crops like peppers and tomatoes in the next couple of years... We hope soon to get to the point where astronauts will be able to choose the crops that they want to grow."

Brande Wulff, from the U.K.'s John Innes Center, an independent research center for plant science, genetics and microbiology, commented on the study: "Entrenched deep within the human mind is a strong urge to conquer foreign pastures," he told Newsweek in an email. "This desire for the unknown, however, must be balanced with our nostalgic, psychological and biological needs for the homely. This study [by Khodada and colleagues] shows that a delicate lettuce leaf can be grown in space and attain essentially the same nutritional [and microbial] quality as on Earth, thus bringing us one step closer to colonizing the extra-terrestrial."