“Our plants aren’t looking too good,” astronaut Scott Kelly tweeted from the International Space Station on December 27, 2015. He was right: The attached picture showed four baby zinnias bathed in magenta light. Three of the four leafy stalks were discolored and curling in on themselves. The station’s garden was struggling to recover from a mold problem. It’s an issue familiar to terrestrial gardeners. And while on Earth, the problem means a trip to the local nursery for replacements, in space you can’t do that.
The zinnias, brightly colored flowers in the daisy family, were part of an experiment called Veggie, whose ultimate mission is to provide crews with a long-term source of food. In prior tests, astronauts had successfully harvested lettuce. The zinnias had a longer growth period—60 to 80 days—and then would bloom, producing neon-hued blossoms that look like they belong in a psychedelic corsage. They were practice for something finickier and tastier than leafy greens: tomatoes. If station crews were ever going to grow something that intricate, they needed to figure out—among other things— how to vanquish mold.
Veggie is a relatively uncomplicated way for astronauts to develop their green thumbs. “It’s a very simple system,” says Gioia Massa, one of the project’s lead scientists. “It doesn’t control much at all.” Instead, the humans do.
Space gardening will be essential someday if space travelers are to go beyond low-Earth orbit or make more than a quick trip to the moon. They can’t carry on all the food they need, and the rations they do bring will lose nutrients. So astronauts will need a replenishable stash, with extra vitamins. They’ll also require ways to make more oxygen, recycle waste, and help them not miss home so much. Space gardens can, theoretically, help accomplish all of that.
Veggie and other systems aboard the space station are helping researchers figure out how radiation and lack of gravity affect plants, how much water is Goldilocks-good, and how to deal with deplorables like mold. Just as important, scientists are learning how much work astronauts have to put in, how much work they want to put in, and how plants nourish their brains as well as their bodies.
For all its potential importance, Veggie is pretty compact. It weighs 41 pounds, just a hair less than the station’s 44-pound coffeemaker. The top—an off-white rectangular box that houses the grow lights—resembles an old VCR. From this, a curtain of clear plastic hangs to encase the 1.7-square-foot planting surface. Astronauts preset how long the lights stay on each day; how brightly they emit red light to optimize photosynthesis, and blue light to control the plants’ form and function. They can also activate a built-in fan to adjust the humidity.
The most important part of Veggie, though, is the fragile bounty it is meant to cultivate. That begins as seeds encased in little Teflon-coated Kevlar pouches. The scientists call them plant pillows. “You can think of it like a grow bag,” Massa says of these packets stuffed with seeds, water wicks, fertilizer, and soil.
People have anticipated this scenario for more than a century. In 1880, science-fiction author Percy Greg wrote Across the Zodiac, a novel about an astronaut who traveled to Mars with plants to recycle waste. Fifteen years later, Konstantin Tsiolkovsky, a Russian rocket scientist, wrote Dreams of Earth and Sky, which laid out how space farers and flora could live together inside a closed system.
In the 1950s, green things burst from book covers and into the lab. NASA and the U.S. Air Force started growing algae to see if it could help with life support (turns out, it tasted bad, was full of indigestible cell walls, and had too much protein). Then, Soviet scientists experimented with nearly self-sufficient ecosystems in which humans survived on oxygen, water, and nutrition produced mostly within an enclosed habitat. In the longest run, a 180-day trial inside a facility called BIOS-3, an earthbound crew got 80 percent of its food from its own wheat and vegetables. Finally, in 1982, plants in space became a reality when Soviet cosmonauts grew Arabidopsis thaliana, a flowering species related to cabbage and mustard, to maturity aboard their Salyut 7 space station. The yield was too small to be a source of food.
Around this time, in the mid-’80s, Veggie’s Massa was in middle school, and her seventh-grade teacher returned from an astroagriculture workshop at Kennedy Space Center with reams of information on the topic. Inspired, a teenage Massa kept taking ag classes as she moved on to high school, and later teamed up with her middle-school mentor for a hydroponics project.
While Massa continued her studies and self-guided experimentation, NASA began building orbital plant-growing apparatus, most notably the Biomass Production System. Designed to be used for experiments on the space station, it was a rectangle with sides each about the length of an arm. Four cube-shaped growth chambers rested like safes inside. Designed by scientists at a Wisconsin-based company, Orbitec, the Biomass Production System joined the space station in 2001. There, Brassica rapa field mustard soon sprouted tall, illuminated by plain white fluorescent light.
When researchers compared the harvest to a control plant on the ground, though, they found that the space mustard had more bacteria and fungus. “The significance of the difference is uncertain,” states NASA’s official conclusion. By which the agency meant it didn’t know why the microbes proliferated, not that their presence wasn’t important. In fact, as Veggie’s mold would show, it was critically important.
NASA retired the Biomass Production System in 2002, but Russian cosmonauts picked up where the U.S. left off. Over the decade, they successfully grew dwarf wheat, leafy mizuna, and dwarf peas. Bonus: In four successive generations of orbiting dwarf peas, the vegetables didn’t show signs of genetic messiness.
Meanwhile Orbitec, in consultation with NASA, cultivated another plant-growing instrument. So when NASA awarded a grant in 2012 for a new space garden, the company had something to show for itself: Veggie, which, unlike its predecessor, was meant to produce food on an edible scale. Massa, by then a postdoc, tested different types of media and crops for the plant pillows. It was the kind of tinkering she’d been preparing for since she was 12. The United States’ first real space garden launched in 2014, not long after Massa advanced from her postdoc to become a Veggie project scientist at the space agency.
All went pretty well for Veggie until the flower flap. Most of its initial edible plants—a lettuce variety called Outredgeous—sprouted as they should have in 2014, and the astronauts shot them back down to Earth for testing. Massa says they’re still working on all the analyses. “But in general, the plants are pretty similar to our ground samples.” When they’re finished, they’ll know about chemical contents like antioxidants, anthocyanin (pigments), and phenolics, which protect plants against stress. Short term, the priority was mealtime: Could we have consumed the harvest? The crew, Massa, and NASA all wanted to know. Yes, it turned out, the produce was microbially safe to eat.
Still, when the astronauts planted a second set of seeds, in summer 2015, Massa ran into a new challenge: With harvest approaching, NASA had no protocol to approve the crew chowing down on the leaves of their labor. “We said, ‘We have only 28 days, and then they’re going to have to eat it,’” Massa recalls. With the clock ticking, management found a way to officially add the lettuce to the astronauts’ diet.
On August 9, Kelly snapped a picture, standing in front of the unfurling greens. His brow was furrowed, faux serious. “Tomorrow we’ll eat the anticipated veggie harvest on @space_station!” he tweeted. “But first, lettuce take a #selfie.” Soon he crunched the harvest live on NASA TV. It might seem like no big deal, but a single leaf can make a big difference to someone who’s been eating rehydrated fare for months. During a later harvest, astronaut Peggy Whitson would use them to wrap a reconstituted lobster salad. “Even with a really good diet with hundreds of items, there’s dietary fatigue,” Massa says. “People get bored. Adding a new flavor or texture—like something crisp and juicy—could spice up your regular meal.”
That’s not the only brain boost. Sure, astronauts can gaze down at Earth and see its most beautiful spots—literally all of them—every 90 minutes. But those places are always out of reach, reminders of how far away sea level is. Having something nearby that photosynthesizes might cheer the crew. “It’s the psychological aspect of something green and growing when you’re far away from home,” Massa says.
In the next growing cycle, the astronauts fostered the ill-fated zinnias. About two weeks in, Kjell Lindgren saw the first warning signs. Water leaked from the wicks that hold the seeds. Then moisture began seeping from the infant leaves, which started to curl in on themselves. Veggie staff on the ground, in charge of the operation, decided it was time to turn the airflow fan from low to high. But an impromptu spacewalk to fix a broken robotic arm delayed the change because, in space, nothing is as simple as flicking a switch on your way out of the spaceship. While reprogramming Veggie’s settings takes only about 15 minutes, NASA prefers astronauts move anything lower priority out of the way when they have a high-priority task.
And then the leaves started to die.
That’s bad enough on its own. But, worse, dying vegetation can be a breeding ground for mold, which had somehow come to space with the astronauts and cargo. Soon, menacing white fuzz began choking the plants.
By this time, Lindgren had returned to Earth, and Kelly had taken over the garden. On December 22, with instructions from ground control, Kelly snipped away the moldy parts like bad spots from a piece of cheese, and swabbed the remaining zinnias and equipment with cleaning wipes. He left the fans on high to help dehydrate the setup.
It was a good try but not without a cost: It made the plants thirsty. Kelly relayed that to ground control and asked to water them. Sergeants who were set on sticking to the drill told Kelly it wasn’t time yet. Not till December 27. “You know, I think if we’re going to Mars, and we were growing stuff, we would be responsible for deciding when the stuff needed water,” Kelly told them, according to NASA’s write-up of the event.
Eventually, they gave autonomy to the person who was actually next to the plants, along with one page of instructions called “The Zinnia Care Guide for the On-Orbit Gardener.”
Under the On-Orbit Gardener’s thumb, half of the zinnias revived, unfurling and growing green. NASA spun the whole thing as a positive: They now knew that crops could survive floods, drought, and disease, and that excising the problem plants and cleaning the remainder could keep the fungus from taking over.
Kelly loved the now-flourishing flowers and carried their container all over the space station for photo shoots, like those people who snap shots of themselves in Hard Rock T-shirts all over the world. “He asked if he could harvest them on Valentine’s Day,” Massa says. He’d been in space, away from everyone except his smelly crew mates for more than 300 days. NASA let him make the bouquet.
It was one of Massa’s favorite moments. “We had been a part of something that gave him pleasure,” she says.
In upcoming Veggie experiments, scientists will learn more about that part of gardening—the mental part. “We’ve heard a lot anecdotally,” Massa says, “but we’ve never been able to collect data.” They’ll also investigate how much farming crewmembers actually want to do, how much is fun versus how much is a chore, how their sense of taste changes in orbit, and which plants can survive human error (no offense, astronauts).
Veggie’s experiments will continue in tandem with those of a brand-new Type-A companion, the Advanced Plant Habitat, an 18-inch-square self-sufficient laboratory with more than 180 sensors and automated watering. Scientists can establish their variables and thus nail down the specific conditions that cultivate plants—and how those plants can cultivate humans. A temperature-control system keeps the air within 0.5°C of the thermostat setting. Sensors relay data about air temperature, light, moisture, and oxygen levels back to base. While the Advanced Plant Habitat will quantify the circumstances for successful gardening, Veggie will help qualify how—and why—humans can facilitate their own food supply. In other words, through the habitat’s tight controls, researchers can learn how to grow which plants best. Then, using those parameters, they can set up a system like Veggie that astronauts get to interact with.
Astronauts assembled the habitat over six hours in October 2017, after it rumbled into space in two shipments. The automated contraption looks like a microwave that could survive… being shot into space. Wires stream from here to there and there to here on a control panel. Red indicator lights blink next to toggle switches. And inside the plant chamber, LEDs beam from the ceiling, illuminating the plants below with concert-stage color combinations. It has red, green, and blue lights like Veggie—plus white, near-, and far-infrared ones.
Robert Richter, director of environmental systems at Sierra Nevada Corporation, which acquired Orbitec in 2014, monitored its progress from the earthbound Space Station Processing Facility. He’d helped design and build the new lab, as well as Veggie and Biomass. When he started in the field, almost 20 years ago, he was a bit naive. “I thought, How hard is it to grow plants?“
He’s partly joking, of course—and he knows, now, that when you’re trying to keep the humidity level within 3 percent of a given number, when you must make and measure light and moisture, and when you maintain the temperature to a fraction of a degree, there’s a long row to hoe between growing some basil in a cup and farming lettuce in space.
The team powered up the unit in November 2017. And by February this year, test crops of Arabidopsis thaliana and dwarf wheat sprouted. Soon, they’ll begin experiments like investigating plants’ DNA and physiological changes. A lot of the previous plant research has been focused on whether things would grow at all, says Robert Morrow, Sierra Nevada Corporation’s principal scientist. Will they reproduce from generation to generation? And are they as productive in space as on the ground?
Yes, he says. Scientists are beyond those basics now. They need to dig into the dirtier details and more-complicated ecosystems. Astronauts, for instance, exhale carbon dioxide that plants can inhale. The plants then exhale oxygen, which humans can inhale. Human waste can become plant fertilizer and hydration. Nothing wasted, everything gained.
Ultimately, Morrow believes, a garden on a deep-space mission will be more like Veggie than like the Advanced Space Habitat. “It’s really not practical to put all the stuff you have in APH in a system like that,” he says. With so many sensors and tubes, lots can go mechanically wrong, and it’s easier to repair a Veggie than an APH. For now, scientists need APH to home in on optimal guidelines for plant growth and understand how leaving the planet changes them so they can instruct future astronauts how to better manage Veggie-esque systems.
Looking toward the future, Massa is interested in observing astronaut interactions with the instruments. “Do you always want to pick your ripe tomatoes, but maybe you don’t want to have to water them every other day?” she wonders. She’ll have a chance to find out because Veggie will grow its first dwarf tomatoes, a variety called Red Robin, early next year.
Other nations continue to experiment too. China, for instance, intends to send silkworms and potato seeds to the moon this year aboard its Chang’e-4 spacecraft. When the silkworms hatch, they’ll create carbon dioxide, which the potato plants will suck up and turn into oxygen, which the silkworms will then take up.
All this research doesn’t just help people above the atmosphere. Creating self-contained growth systems might help farmers on Earth grow crops year-round or foster plants with extra protein and high yield. Someday, the work will lead to gardening systems substantial—and stable—enough to support space journeyers. Then, those travelers can wrap anything they want in lettuce and crunch their way through the cosmos.
Contributing editor Sarah Scoles is the author of Making Contact: Jill Tartar and the Search for Extraterrestrial Intelligence.
This article was originally published in the Summer 2018 Life/Death issue of Popular Science.