"They say once you grow crops somewhere, you've officially colonized it."
So declares Mark Watney in the 2015 blockbuster "The Martian." Stranded on Mars, the astronaut (played by Matt Damon) survives on greenhouse-grown potatoes fertilized with his own poop while awaiting the rescue mission that will return him to Earth.
Of course, Watney and those spuds are pure fiction. Though astronauts aboard the International Space Station now enjoy salads made with lettuce harvested from the station's Veggie Plant Growth System, they rely mostly on freeze-dried meals brought from Earth.
As for growing crops on the moon or other planets, no one has yet devised a workable plan. But we're working toward just that.
Earlier this year, scientists at the International Potato Center (CIP) in Lima, Peru, announced initial success in growing potatoes inside a small chamber that partially simulates the harsh growing conditions on Mars. The chamber couldn't mimic Martian gravity (which is about one-third of gravity here on Earth), but it did simulate the high carbon-dioxide levels, low atmospheric pressure and temperatures, high radiation levels — and even the dry, salty soil of the red planet.
As part of an experiment called Eu:CROPIS, Germany's space agency, the German Aerospace Center (DLR), next year will launch into orbit a satellite containing a pair of tiny soil-less greenhouses. The satellite will use its own rotation to simulate lunar gravity (one-sixth of Earth's) for six months and then Martian gravity for another six months. Under these conditions, scientists on the ground will try their luck growing tomatoes from seeds, watching their success with cameras.
The tomatoes will be fertilized with synthetic urine — to mimic one type of natural fertilizer astronauts on the moon or on Mars would have at their disposal. "We have to recycle everything in a closed environment, so we have to solve the recycling of human and bio waste — urine, feces, old leaves, rotten fruits, leftover food — to produce a fertilizer solution for plants," Jens Hauslage, leader of the German experiment, told NBC News MACH in an email.
We'll likely need to bring our own microbes to help our Martian compost along. Eu:CROPIS will test a filter system for the greenhouse: lava stones "infected" with microbes that can produce oxygen and convert urine into plant nutrients. But Hauslage said it's not clear how these colonies will function in space. "We know that the growth of bacteria is different under microgravity, so the question is how will they grow under lunar and Martian gravity?"
David Ramirez, one of the CIP scientists, said one of the most important challenges for future missions to Mars will be soil-based agriculture. "This is the only way to guarantee reduction of resources from Earth and try to get a self-sufficiency of food supplies," he said. But, he added, the extreme salinity of Martian soil will be a big obstacle, so it will be crucial to find potato varieties that are especially tolerant to salty soil.
How do the CIP potatoes taste? The scientists haven't tried them. But they say some of the potato varieties that performed best in the Mars-like conditions are already being grown commercially in salty soils in China, Bangladesh, and Peru.
As for what a Martian farm will look like, picture a greenhouse with a few twists. NASA has been working on a Prototype Lunar/Mars Greenhouse that's cylindrical in shape and designed to be buried underground to protect it from radiation.