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Would You Eat a Tomato Grown With Your Own Pee?

If you're an astronaut on Mars one day, you might not have a choice.
Maarten Wouters/Getty Images

Left behind on Mars, Matt Damon's botanist-astronaut character improvises a potato farm on the Red Planet's surface in the 2015 movie The Martian. Its sustenance? Water extracted from rocket fuel and a vat of human poop.

Food has been one of the greatest challenges of space exploration since humans began infringing on the final frontier. The canned, dehydrated, and otherwise space-readied options sent up in spacecrafts couldn't support any longstanding settlement on a moon or new planet, so space agencies have been intensely interested in space farming, which would provide fresh, nutrient-dense food to space travelers. So far, the only crops raised off the planet have been some hydroponically-grown heads of cabbage and lettuce tended to by green-thumbed astronauts at the International Space Station.


The German-government space agency, DLR, will give space farming its most extensive test yet when the Eu:CROPIS satellite begins its orbit in July, hitching a ride with the latest rocket launch of Elon Musk's private space exploration company SpaceX. Eu:CROPIS—short for the clunky Euglena and Combined Regenerative Organic-food Production in Space—will be outfitted with miniature automated green houses with tomato plants installed. During its 18-month mission, the satellite will first simulate the gravity of Earth's moon (0.16 times that of Earth's) and that of Mars (0.38 times that of Earth). Cameras and sensors on board will track how well tomatoes do under gravity set to that of each astronomical body.

The sustenance for the tomatoes? Like Matt Damon, the Germans are reaching for bodily waste: The plants will be grown in synthetic urine. Salt-rich pee could be the best—and most readily available—plant nutrient in space. Urine is also continually recycled on space missions, filtrated, purified and turned back into water in habitats where space is at a premium and there is no natural hydration.

Richard Hollingham, a reporter for the BCC, visited the lab of DLR's plant physiologist, Jens Hauslage, near Cologne. Hollingham found "plenty [of] urine swilling around—in vats, funnels and hoses," which the scientist was using for tests of the tomato strain set for orbit.

"The smaller columns can handle the urine of one person for a day," Hauslage explained, pointing out the equipment. "The big columns can handle the urine of four to six people."

The tomatoes were bred to flourish in space, which Hollingham said may have affected their taste: "To be brutally honest, it's not the nicest tomato I have ever tried: The skin is a little tough and the taste is slightly bitter. But it is, nevertheless, a healthy, edible tomato."

Given the other options in space, they will probably do.