In the fall of 1995, a team of researchers clipped 10 leaves from a potato plant, nestled them into beds of moistened soil, and shot half of them into space.
The mission, conducted aboard the Space Shuttle Columbia, was a gamble, to say the least. Decades of research had already hinted that plants could, in fact, flourish outside of Earth’s atmosphere. These weren’t even the first spuds to ride a rocket—that had happened some 25 prior, when a team of Russian scientists loaded three taters onto a spacecraft and bid them adieu. But the prospect of getting a cut stem to yield an edible tuber in the vastness of space was far from a guarantee.
Within a couple weeks, the stems of the five cuttings that had remained here on Earth had swollen into gumball-sized potatoes. And, orbiting a few hundred miles off the surface of Earth, their weightless counterparts did the same.
The extraterrestrial taters would eventually make their way back to Earth, where a battery of tests would reveal that they tubers were alarmingly… normal. In fact, they were nearly indistinguishable from their grounded brethren in most respects. Even without gravity, the spuds had fared just fine.
It turns out the same is true of most of the crops researchers have launched into the cosmos. Despite eons of evolution here on our home planet, Earth’s plant life is surprisingly amenable to space travel—especially when given a little extra TLC from their human caretakers.
On the whole, plants on and off planet “look pretty much the same, if you don’t look too closely,” says Anna-Lisa Paul, who studies the biology of plants in microgravity at the University of Florida.
That’s very good news for the cosmic jetsetters among us. Though the menu of spaceflight has expanded tremendously in recent years, astronauts still rely mostly on packaged food. That’s a pretty monotonous diet—and a lot of baggage to carry aboard a spacecraft. If we humans are to truly go the distance vis-à-vis space travel, we’re going to need more sustainable sustenance, says Gioia Massa, a plant scientist at NASA’s Kennedy Space Center.
As such, there’s a decent argument for sending spuds into space. These tubers teem with several vitamins and minerals, and pack a decent amount of protein for a starch. They also boast a high harvest index, or the fraction of their mass that’s edible, says Raymond Wheeler, a plant physiologist and potato expert at NASA. “You can get about 80 percent of a [potato’s mass] to tuberize,” he says. “They’re a good, nutritious crop.”
There’s a catch, though: Raw potatoes aren’t terribly palatable—and there aren’t ovens and deep fryers in space.
In fact, any crop that needs to be cooked before it’s eaten presents an additional hurdle for hungry astronauts. And so, aboard the International Space Station (ISS), researchers like Massa focus on roughage that can simply be plucked from its stem.
One of their ongoing experiments, Veggie—which Massa has been involved in since 2014—is a suitcase-sized space garden that can support about six plants at a time, supported on porous pillows of fertilized clay. Instead of soaking up sunlight, the sprouts spend their days beneath LEDs, bathed in a soft magenta glow (a mix of the red and blue wavelengths that plants like best).
Already, the team has gotten several kinds of salad greens to sprout, and in the summer of 2015, red romaine lettuce became the first plant to be grown, harvested, and eaten in space.
But when things get extraterrestrial, even fast-growing greens come with challenges. “Growing a large plant is a huge undertaking in microgravity,” says Robert Ferl, a plant biologist at the University of Florida and Paul’s collaborator. “When you really want to control its water, nutrition, carbon dioxide, and everything else, it becomes a monumental engineering task.”
In the absence of gravity, fluids like water and air have trouble flowing, clumping instead into stubborn bubbles. Fans are a pretty straightforward fix for the airflow issues, but keeping plants hydrated is a bit more of a logistical headache.
With Veggie, caretakers dispense liquid to plants with a syringe, a process that still requires manual labor. In a companion experiment called the Advanced Plant Habitat—a mostly self-sufficient growth chamber that continually monitors temperature, light, moisture, and oxygen levels—scientists are tinkering with ways to automate this process entirely.
“The ultimate goal would be to minimize astronaut labor,” says Won-Gyu Choi, a plant biologist at the University of Nevada, Reno.
Even with all this coddling, though, plants aren’t fooled: They’re still very much aware that they’re in space, Paul says. In response to low gravity, plants initiate a whole set of changes at the level of gene expression—many of which scientists like Paul, Ferl, and Choi are still puzzling through back here on Earth.
Awareness isn’t necessarily a bad thing, though. Plants’ exquisite sensitivity to their surroundings tells them how best to adapt—and flexibility is key when you’re tethered to the ground. Unlike us, plants can’t uproot and move into more accommodating territory when times get tough, Massa says.
In space, there’s no gravity to guide roots as they spread away from seeds in search of water and nutrients. So the plants make do with other cues, turning on a set of sun-sensitive genes that instructs roots to snake away from strong light. A few years ago, a team of researchers led by Paul and Ferl was astounded to see that this reprogramming was enough to allow plants aboard the ISS to unfurl their roots into a pattern similar to those seen on Earth.
It’s unclear whether this light-driven strategy will work in more foreign locales, like the Moon or Mars, which both have more gravity than an orbiting spacecraft. Earlier this year, cotton seeds aboard China’s Chang’e 4 lunar lander became the first to germinate on the Moon, sprouting small green shoots inside a tiny biosphere within the probe, but no one was around to keep tabs on the plants’ growth. Scientists also don’t know whether the lunar or Martian soil—a rocky, ash-like material called regolith that lacks many nutrients—will ever be hospitable to plant life, Massa says.
There are also a few lingering uncertainties in the arena of food safety. Where humans go, so too do their microbes—friend and foe alike. Though many plants depend on bacteria, they can also harbor agents of disease, and researchers still aren’t sure how the dynamics of illness and immunity play out in space. “Microorganisms are likely going to have a huge role in any space agriculture system...but food safety is also one of our biggest concerns,” Massa says.
Still, researchers believe the potential benefits of astrobotany far outweigh the costs. In addition to their nutritional perks, plants provide oxygen, as well as a sink for human waste. Some event manufacture antioxidants that could safeguard astronauts against the perils of UV radiation, which abounds in space.
Green stuff is also good for mental health—especially so far from sea level, Choi says. Homesick space travelers may find gardening psychologically soothing, or take comfort in simply being around familiar leaves and blooms.
Looking ahead, the highest priority plants remain those that have a high harvest index and grow quickly and robustly, Massa says. Ideal crops will also be chock full of key nutrients that are tough to package, like potassium. Flavor can’t be neglected either: “If it doesn’t taste good, no one will eat it, no matter how nutritious it is,” she says.
Cabbage, kale, and lettuce are among the crops that have already sprouted successfully in space. Massa hopes to add some fruiting plants, like peppers, to the ISS within the next year—ingredients that could spice things up at mealtime.
Choi’s plant passion du jour is tomatoes, which, in addition to their appealing taste, pack in an impressive number of vitamins and antioxidants, he says. A few genetic tweaks could enhance their nutritional value, he says, or make the entire tomato plant edible, even when the fruits are still green.
These top tier crops all have something in common: They can be consumed straight off the stem or vine—which, unfortunately, isn’t true of many tubers, like potatoes.
So, is there still a future for these second-string spuds? “I hope so,” Wheeler says. Potatoes still have a lot going for them nutritionally. And when ovens and other appliances make their way into space, potatoes will still have a leg up on other staple crops like wheat or soybeans, which often require additional processing before they can be cooked.
Fresh, supplemental crops like lettuce will do well aboard the ISS, Wheeler says. But farther from Earth, humans will need more autonomy. When it comes to lunar or Martian agriculture, “that’s the stage where more stable, agronomic crops [that supply more energy] can be considered,” he says. “I’m hoping we get to that point.”
There’s no telling what that future will bring. But for now, even in the vastness of space, it would seem that everything’s coming up Russets.