In The Martian, a stranded NASA astronaut is forced to turn a planned four-week mission on the surface of Mars into a marathon for survival. His only chance to have enough food to last until he's rescued is to turn his habitat into a space farm, using the only crop he has available: potatoes.
Space farming researcher Bruce Bugbee tells PM that the story gets it pretty much right. Bugbee, who runs the Crop Physiology Lab at Utah State University, has been studying how to grow food crops on spaceships for NASA for the last 30 years.
Let's start with fictional astronaut Mark Watney's crop itself: If you're forced to rely on just one crop to grow in a space habitat, "potatoes are a good choice," Bugbee says. "They're a good producer of carbohydrates and they can be a big part of the diet."
Of course, the nutritionists with whom Bugbee and his students consulted weren't too crazy about such extreme monoculture. "They say stuff like, 'Are you nuts? We haven't ever tried that before. We'd need 30, 40 crops at the minimum." But while it's good advice for those of us living on Earth to diversify our diets, it's hard to imagine a scenario in which there'd be enough room for that many different kinds of plants on any sort of space mission, even on an extended one to Mars.
Bugbee figures three or four crops will have to do. In The Martian, Watney is down to just the one, but he also has plenty of protein bars and vitamin pills to break up the monotony. Bugbee says the science isn't there yet to show how well someone would do surviving on such a monotonous diet for so long, but he doesn't see why Watney couldn't get by.
Sealed-up spuds
The two biggest challenges for growing crops in space are farming in microgravity and the need for a completely closed environment, Bugbee says. On Mars, the first is a non-issue; there's not as much gravity as there is on Earth, but there's more than enough to get plants growing in the right direction and to keep water flowing down to their roots. By far the biggest challenge a real-life Watney would face is closure.
"If we're really going to do this, you can't open a window and throw stuff out," he says. "Every speck of everything has to be recycled. That's a tremendous challenge." That includes, of course, human waste. "As he says, 'I'm growing stuff in my own shit.'" According to Bugbee, an important detail here is that Watney doesn't just dump the waste right onto the plants. He mixes it with compost made of decomposing plant matter first. This helps break down any potential pathogens in the waste.
Keeping the system sealed so that nothing can leak out isn't a big deal at this point, Bugbee says. "We know how to seal things. That's no longer a tall pole in the tent." The bigger problems, he says, in addition to recycling everything, is maintaining what he calls buffers—extra storage for things like water and oxygen that can be filled from or emptied into the environment as needed.
"Let's say you're Mark Watney and everything is in balance on Mars for you, and now two people come for dinner," Bugbee says. "Not only do you need food for those people, but as soon as they walk in the door, you need more oxygen for those people. Right now. They're breathing." Stored oxygen would have to be on hand to make up the difference.
Watney, of course, could only dream of having guests over dinner. Even so, Bugbee says, he'd still need buffers to account for the other living things other than him residing in his jury-rigged space farm: you know, the plants themselves. As the plants grow and multiply, they'll need more CO2 and water over time, and they'll also put extra oxygen into the habitat. Buffers that can absorb and release gases and water are needed to maintain the optimum balance in such an environment as conditions change.
Spaceship Earth has been recycling gases and water and nutrients for eons. We also have enormous buffers in the form of the oceans. All of which point to what Bugbee feels is one of the most valuable aspects of space crop research: It helps us better understand our own ecosystem and to improve terrestrial agriculture.
Space hydroponics
The only thing Bugbee would do differently than Watney if he were to plan a Mars mission? Aside from bringing along an extra crop or two—say, some salad greens—he'd grow the plants using hydroponics instead of Martian soil, or regolith, as Watney does. Watney has no choices given the equipment on hand, but hydroponics would make it way easier to control the recycling of nutrients and water. "But there's no reason he couldn't use the soil of the planet," Bugbeehe says of Watney. The soil does the job of retaining water and holding up the plants.
As for the movie itself, Bugbee says, "I hope it really catches on because it helps explain what we do in agriculture on the earth and how essential it is. We take it all for granted."
Michael Belfiore is frequent PM contributor. Find him online at michaelbelfiore.com.
