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Thursday, May 23, 2024

Growing Peppers on the ISS Is Just the Start of Space Farming

Unburdened by the constraints of gravity, red and green peppers jut out at 45-degree angles inside the Artificial Plant Habitat (APH), a sort of space terrarium not much larger than a microwave. Four chile pepper plants stand effortlessly upright, despite the dozens of glossy fruits weighing them down. These plants have lived entirely in space; their leaves have never been chewed on by insects or rustled by a summer breeze, their stems are unfamiliar with bending toward the sun’s arc across the sky. Scissors glint under the tank’s white and blue lights as astronaut Mark Vandahei and his team snip the stems of those that are ready for harvest. The peppers whirl around their heads until the astronauts catch them and tape them against a board to photograph.

Back on Earth, the Plant Habitat-04 team of engineers and plant scientists are observing and conferring with the astronauts. Of the 26 peppers in this batch, only the 14 finest will stay on the International Space Station for consumption. The rest will be wrapped in foil, sealed in a Ziploc bag, then frozen at a brisk –80 degrees, until they can come roaring back to Earth in the next cargo capsule to be studied later. Now, after a 138-day growth cycle, the astronauts remove the plants from the module and trash them. Project Plant Habitat-04 is complete. It’s taco night on the ISS.

Since 2014, NASA has experimented with growing lettuces, brassicas, and zinnias in space, an endeavor that relies on highly specialized technology over 50 years in the making. This fall’s two successful pepper harvests, in October and November, will provide data on the nutritional and psychological benefits of growing vegetables on-craft, as well as a crop’s ability to reliably produce long-term in microgravity. While controlled environmental agriculture is not new, the APH experiment represents an evolution in specialized growth habitats. It doesn’t aim to re-create Earth’s conditions, but to perfect each isolated variable of plant growth in the clinical environment of a spaceship.

“The advanced plant habitat is the most complex plant growth system on orbit today,” says Lashelle Spencer, a plant scientist at NASA’s Kennedy Space Center. Its more than 180 sensors control and monitor temperature, humidity, and carbon dioxide. The astronauts can adjust the color and intensity of the light, and how much moisture the plants’ roots are getting. It waters itself.

It’s the day after Thanksgiving, and Spencer has been at Kennedy since 5 am to facilitate the peppers’ final harvest. As part of the project team, she played a crucial role in preparing the seeds that were sent hurtling into space in July and guiding the astronauts through maintaining the plants in orbit. When the fruits return, she’ll be running their microbiological, molecular, genetic, and nutritional analysis. Though astronauts can spend upwards of 100 days in space, their on-mission meals come dehydrated and pre-packaged; their vitamins and minerals are isolated in supplements, which lose nutritional value the longer they’re stored. Spencer’s goal is to create the conditions necessary for cultivating healthy plants in space, so those plants can sustain healthy astronauts on long-term missions. Astronaut food is great, she says—“especially the shrimp cocktail. But you're missing that crunch. You're missing that fresh pop of flavor, the green flavors that's not there in that packaged food.”

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The sensory experience of growing productive crops can also help mitigate the psychological effects of long-term space travel. There’s a certain emotional connection to food that doesn’t come from a dehydrated space pantry. Spencer says the team cracked open the door of the APH every day to observe their vegetable companions with all the tenderness of home gardeners. When harvest day came, they batted their bounty around the ISS, taking selfies and delighting in watching the fruits pirouetting around the spacecraft. Even when the sharp heat of that first bite made them scrunch up their faces, the astronauts still reveled in the chiles, which they ate with fajita beef and rehydrated tomatoes and artichokes.

“We were thinking no heat, so that [the peppers] wouldn’t be dangerous, but maybe the astronauts need a little spice in their life,” says Paul Bosland, who along with his colleagues at the Chile Pepper Institute genetically engineered the Española Improved chile pepper seeds grown in Plant Habitat-04. (They are the new extraterrestrial pride of New Mexico.)

Working with NASA, Bosland cultivated a variety that could accommodate both the nutritional needs of astronauts as well as the logistics of growing a plant in space. Bosland’s crosses are designed with Mars in mind: Bred to be early-maturing, compact, efficient under low light, resilient in low-pressure environments, and to pack three times the Vitamin C of an orange to prevent scurvy.

Every aspect of the plants’ growth cycle was mechanized. Seeds were planted along with a specially-developed fertilizer in a soil-less, arselite clay medium, and each quadrant was equipped with salt-absorbing wicks that protected the seedlings from scorching due to the saline residue of the fertilizer. Once they germinated, the astronauts thinned the plants until only four remained. The 180-plus sensors controlled every aspect of their growth conditions, including adjusting the colors of the lights to stunt their growth and keep them at a manageable two-foot height.

Despite the highly-controlled growing environment, microgravity affected the plants in some unforeseen ways. Without a gravitational tug, the flowers and their pollen-laden stamen grew facing upward. Ironically, that thwarted how the APH was supposed to pollinate them—by using fans that pulsed soft bursts of air meant to mobilize pollen, the way a breeze would. Instead, astronauts had to fill in as knock-off bees, manually pollinating them one plant at a time.

Microgravity also posed challenges to watering. As demonstrated by the Canadian Space Agency, water behaves differently in microgravity than on Earth. Unable to fall, flow, or ascend, water creates an aqueous layer enveloping the surface of whatever it clings to. But clingy water can suffocate a plant’s roots; as Bosland notes, “chile peppers don’t like their feet wet.”

This was one of the challenges APH engineer and Kennedy Space Center research scientist Oscar Monje had to solve. The system recycled water in a closed loop; the entire experiment used approximately the same amount of water as an office water cooler. Moisture sensors regulated the exact amount that adhered to a root’s surface. Then any water unabsorbed by the plant would evaporate after humidity sensors created the arid environment peppers crave. It’s not a technology that’s ready to roll out on say, the moon or Mars. “The APH uses a watering system that's not sustainable for crop production right now. But it's good enough for conducting space biology experiments,” Monje says.

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That said, he’s already thinking about ways to adapt farming to surfaces of other planets, like by reusing organic material. “As we move toward Mars, instead of bringing that nutrient solution all the way from the Earth, we have to start recycling some of the biomass that's inedible,” he says. “For example, the peppers, we only need the pepper. But the leaves or stems, the roots, maybe we can squeeze some of those nutrients back out.” Methods like composting food waste or burning inedible plant matter for biochar production might then recycle nutrients back into a closed-loop growing habitat.

Bioregenerative practices are the name of the game for long-term space crop production. The challenges astronauts face to farm in space are steep, from lifeless soil and harsh and dusty conditions to water that must either be extracted from ice or brought from Earth and recycled. Recycling organic material will be essential for sustained cultivation in an environment bereft of soil microbiomes. Earthbound farmers who also seek to restore and maintain soil health have developed regenerative techniques to steward interdependent animal, fungi, and plant ecosystems that recycle organic material, create appropriate growing conditions, and amplify genetic diversity. Translating these ideas for space use will guide the future of off-planet farming.For example, in February, an international group of researchers published an editorial arguing that autotrophs like algae and cyanobacteria must form the backbone of a bioregenerative system for spaceflights because of their talent in recycling air and water through photosynthesis and transpiration. They play a crucial part in ecosystems that sustain life on Earth, and their role as energy synthesizers is a piece of the regenerative puzzle. As one step toward that idea, researchers at the University of Louisiana have experimented with humanure through growing microalgae on the ISS in an effort to recycle human waste into biomass. Though the experiment found that the system was not a fully closed loop and would require external inputs, microalgae were able to reclaim substantial levels of oxygen and biomass from urine and wastewater on the ISS.

Working with mycologist Paul Stamets and TransNautica, NASA researchers are exploring creating soil by seeding asteroids with fungi. Fungi’s role as Earth’s most integral decomposers isn’t limited to breaking down complex organic and toxic molecules; it can also create hospitable environments for communities of microorganisms, a soil microbiome fertile enough for crops. Using fungi to break down carbon-rich asteroids into organic soil may allow for complex agricultural systems and enough green space to sustain people in a terraformed habitat.

Techniques for energy recycling and waste management have played integral roles in how agriculture has developed on Earth. There’s still a long way to go before Carhartt-clad astronauts haul wheelbarrows of asteroid biomass on Mars, or braid together chile harvests to flash-freeze on the moon. But the peppers of Plant Habitat-04 mark the start of translating those techniques for a space habitat. The experiment is helping gather the data necessary to determine the nutritional content of crops grown in space, and therefore how many people they can feed, and for how long. Though much is still unknown, Spencer is certain of one thing that future astronauts will need to do: “I think in an optimal world, a scientist like me would say that they would be growing plants from day one. From the day they left to the day they came back, they would be growing them.” The WIRED Resilience Residency is made possible by Microsoft. WIRED content is editorially independent and produced by our journalists. Learn more about this program.


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