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

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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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