For decades, meals for astronauts during their trips off planet have mostly consisted of prepackaged dehydrated or freeze-dried food, occasionally garnished with terrarium-grown lettuce (
Fig. 1) [
1], [
2]. With longer-term missions to extraterrestrial outposts on the near horizon, a US National Aeronautics and Space Agency (NASA) competition now in its final stages aims to meet the nutritional needs of astronauts on deep space voyages. An added benefit could be innovations in low-resource food production that could help feed Earth’s still growing human population.
In the first crewed lunar mission since 1972’s Apollo 17, NASA plans to fly four astronauts around the Moon in 2025 as part of its Artemis program [
3]. Its larger plan, however, is for humans to return to the lunar surface later this decade, at first for days at a time but eventually for weeks, months, and even longer. Early, short-duration lunar missions will be supplied with dehydrated and freeze-dried food like what astronauts eat on the International Space Station (ISS), and where a shuttle resupplies the pantry every two to three months. However, extended lunar missions, as well as journeys to Mars, will require moving away from carried supplies and costly resupply from Earth [
4]. Additionally, food diversity is crucial for astronauts, who tire of repeatedly eating the same thing; menu fatigue, especially for humans confined in the tight quarters of a space capsule, can lead to loss of appetite, shrinking body mass, nutritional deficiencies, and other issues [
5], [
6].
“Realistically, the first Mars missions will probably still rely somewhat on prepackaged food, but that is not sufficient to cover all the nutrient requirements of astronauts—its shelf-life stability is limited, and the vitamins break down over time,” said Yuri Griko, senior scientist at NASA Ames Space Biosciences Research Branch in Mountain View, CA, USA. “Growing fresh food is absolutely necessary for long-term missions.”
To address this need to sustainably produce food on future space missions, NASA launched the Deep Space Food Challenge (DSFC) in January 2021 in coordination with the Canadian Space Agency (which is running a parallel competition) [
7]. Contestants were asked to create, for a crew of four on a three-year, round-trip mission, food technologies or systems that require minimal resources while maximizing the production of safe, nutritious, and palatable food. The inventions did not need to provide a crew’s entire diet but had to offer a variety of nutritious foods.
About 200 companies entered phase 1 of the competition, submitting detailed concept proposals. In October 2021, NASA announced phase 1 winners: 18 US teams, each awarded 25 000 USD, and ten international teams which were not eligible for cash prizes [
8]. These 28 teams moved into the competition’s phase 2 in which each group built and demonstrated kitchen-scale prototypes of their inventions. In May 2024, NASA announced its eight phase 2 winners, including five US teams, each awarded 150 000 USD, and three international teams [
9]. In the final, phase 3 of the competition, the teams are testing their approaches and engaging in simulated flight operations, with announcement of the winners expected in August 2024. The top-scoring US team will win 750 000 USD, with 250 000 USD going to each of two runners up; any other team that proves technological readiness will receive 50 000 USD [
10].
One of the US finalists, the New York City, NY-based AIR COMPANY, designed a renewable energy-based system that combines the CO
2 exhaled by astronauts with water and small amounts of yeast to produce alcohol, which then is fed to bacteria, producing proteins that can be formed into edible food [
11]. The company already makes plane fuel, vodka, and perfume from processed CO
2. “It was a fun challenge for us to learn how to set up a biological system,” said Mahlet Garedew, the company’s innovation program manager. “The taste is like protein powder or the vegan meat substitute seitan—it can easily be used to make protein shakes or as a way to boost the nutritional value of other dishes such as salads.”
Another US finalist, Riverside, CA-based company Nolux, developed a method of artificial photosynthesis. Like AIR COMPANY, Nolux’s method exploits exhaled CO
2, using electrolysis to convert it and water into oxygen and acetate. The acetate is then pumped into a growing chamber to feed oyster mushroom spores, which can grow to full size mushrooms in the dark in a matter of weeks. The process also works to grow algae and yeast and, according to the company, converts energy into biomass more efficiently than photosynthesis [
12].
“The efficiency of agriculture systems we have on Earth is very low, given the energy and resource input relative to the biomass produced that can be eaten,” said Feng Jiao, a Nolux team member and professor of energy, environmental, and chemical engineering at Washington University in St. Louis, MO, USA. “With our technology, we try to use limited resources very efficiently to produce the most edible biomass possible.”
Rounding out the five US finalist teams are Interstellar Lab (Merritt Island, FL), Kernel Deltech USA (Cape Canaveral, FL), and Ascent Technology (Boulder, CO). Interstellar Lab has built a set of modular toaster-size capsules, each with its own humidity, temperature, and watering system. The system, called Nucleus, would allow astronauts to cultivate edible fungi (
Fig. 2), vegetables, or even insects such as protein-rich black soldier fly larvae [
13]. The Kernel Deltech team developed compact bioreactors that use limited resources to grow and harvest
Fusarium venenatum, a species of protein-rich fungus with a decades-long history of human consumption as Quorn, a brand of meat substitute products developed by a Stokesley, UK-based company with the same name [
14]. Ascent Technology was the only team to take on the challenge of cooking food safely in microgravity. Its invention, called SATED (safe appliance, tidy, efficient, and delicious), is a food processor-sized centrifugal oven that cooks food as it spins, enabling astronauts to prepare a variety of meals, including pizza, omelets, and ice cream [
15].
The three international finalists are Melbourne, Australia-based Enigma of the Cosmos; Gothenburg, Sweden-based Mycorena; and Helsinki, Finland-based Solar Foods. Enigma of the Cosmos developed a system, 2 m
2 in size, that produces up to 0.7 kg of leafy greens and microgreens per day (
Fig. 3) [
16]. Mycorena’s system, Algae-Fungi Circular Solution (AFCiS), produces a type of protein from fungus that is high in protein, fiber, vitamins, and nutrients, and low in fats and sugars [
17]. Combining the relatively flavorless protein with spices could yield a wide range of foods, such as burgers or nuggets. The AFCiS system comes equipped with a nozzle to 3D-print the fungus product into the shape of the desired food product. Solar Foods’ protein-heavy powder, Solein, is readily incorporated into various dishes (
Fig. 4); the powder consists of safe-to-eat dehydrated hydrogen-oxidizing bacteria grown in a fermentation process that metabolizes CO
2 and hydrogen procured as a by-product of standard life-support systems aboard crewed spacecraft [
18].
In addition to the DSFC, NASA has supported a handful of other programs focused on growing plants in space, including the Vegetable Production System (Veggie), the Advanced Plant Habitat (APH), and the Flex Aeroponic System (FAS) [
19], [
20]. Veggie is a small, low-power system that uses a hydroponic system and light-emitting diode (LED) lights to grow plants in a controlled environment. APH is a self-contained capsule that uses LED lights and a porous clay substrate to deliver water, nutrients, and oxygen to plants. FAS is a lightweight inflatable growing chamber with mesh holders upon which seeds can be placed and misted with a nutrient-rich spray.
All the food-growing systems that advanced to the final DSFC stage rely on producing food in capsules, bioreactors, or other high-tech laboratory equipment. A few intrepid space food pioneers are attempting to grow it the old-fashioned way: in soil—or, rather, lunar “soil.” Researchers at Texas A&M (College Station, TX, USA), for example, have demonstrated a system for growing chickpeas in a synthetic media meant to replicate lunar regolith, the loose collection of broken rock and dust found on the Moon’s surface [
21]. Unlike the soil on Earth, lunar regolith lacks nutrient-rich organic matter and microorganisms critical for plant growth. The Texas A&M scientists added fungi from terrestrial soil plus worm manure to create a fertile moondust mixture. While these amendments helped sequester toxic contaminants from the dust, improved its water retention, and increased plant tolerance, the chickpeas grown in it took 20% longer to mature and showed symptoms of stress [
21].
Similar work by scientists at the University of Florida (Gainesville, FL, USA) reported in 2022 showed that plants such as
Arabidopsis thaliana—a small plant in the mustard family related to cauliflower, kale, and turnips—can grow from seed in teaspoon volumes of actual lunar regolith collected from the Apollo 11, Apollo 12, and Apollo 17 Moon missions [
22]. However, while the regolith-sprouted plants germinated at the same rate as their counterparts grown in Earth soil, they had stunted root systems, slower growth, less extensive leaf canopies, and heightened stress responses.
As for plants actually grown on the Moon, China was the first country to achieve this feat, sprouting a cotton seed within a chamber inside the Chang’e lunar lander on its 2019 mission to the far side of the Moon [
23]. An Australian National University (Canberra, Australia) research team plans to grow plants from seed on the Moon [
24]. Among the seeds the team will send aboard Israel’s Beresheet 2 lander in a 2025 lunar mission will be an Australian grass called
Tripogon loliiformis, which is known as a “resurrection plant”—a plant that can spring back to life after long stretches of dormancy and dehydration upon adding water [
25]. Future such efforts may benefit from on-going research at the Norwegian University for Science and Technology and SINTEF in Trondheim, Norway. The SINTEF group is working on a plan to grow plants on the Moon in hydroponic chambers, utilizing water in the Moon’s ice caps, astronaut’s urine, and a cellulose-based material used to pack fragile mission equipment [
26].
Astronauts are not the only ones who could benefit from innovations in super-efficient food production. The United Nations’ Food and Agriculture Organization estimates that food production must increase more than 50% by 2050 to feed a human population of nearly 10 billion [
27]. At the same time, climate change will continue to threaten crops worldwide, exacerbating global food insecurity. In addition, the world’s current food production systems are resource intensive, contributing 20%-40% of all greenhouse gas emissions [
28]. NASA required its DSFC teams to address these problems by exploring how their inventions might also help feed humans on Earth [
7]. The hope is that these innovations, designed to work in the low-resource environment of space, could help feed Earth’s growing population more sustainably and address food insecurity in inhospitable climates and desolate regions. “Utilizing CO
2, which we all know is an abundant resource, to create an edible protein has the potential to revolutionize agriculture and food production if deployed responsibly,” AIR COMPANY’s Garedew said. “This could also displace an impactful portion of our dependence on traditional farming methods that are major contributors to global greenhouse gas emissions.”
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