NASA astronauts will begin growing and eating their own greens on the International Space Station this December.

Some plants, especially weeds, can grow in the harshest of conditions. But cultivating lettuce in outer space?

That’s what astronauts will be doing in December when NASA sends them on a very special trip to the International Space Station.

Vickie Kloeris manages the International Space Station’s food system for the National Aeronautics and Space Administration. She told Healthline that growing edible lettuce in space will eventually lead to an array of inter-planetary produce.

And it’s all to prepare for a manned trip to the red planet Mars around 2030.

“This is the first time, to my knowledge, that U.S. crew members ever have been given permission to eat the vegetables they grow,” Kloeris said. “Flight surgeons have given it the green light.”

NASA has been experimenting with how to grow plants in space for many years. Astronauts have brought back samples of lettuce grown on the final frontier, and NASA has verified that the microbial load is safe and the greens are edible.

It costs NASA $10,000 a pound to rocket nutrients skyward on space missions. But even more than the money, there are issues of having enough space to store the food, as well as keeping it tasty and fresh on long missions.

Kloeris and others have already grown vegetables in space simulators on earth. To do so, she spent 91 days in an isolation chamber that mimicked the environment of a spacecraft.

The produce is grown under bright, purplish lights specially designed for growing lettuce. “Lettuce is a good choice in micro-gravity because it’s a pick-and-eat crop,” Kloeris said. “Cherry tomatoes could be the next thing. You can’t grow wheat and mill it in micro-gravity—that’s just not going to work.”

NASA estimates that it will take six months to get to Mars and six months to get back. Astronauts will likely remain on the planet for another 18 months.

For the first trip, NASA astronauts probably won’t be food self-sufficient. Besides, Kloeris said, the crew could not survive on lettuce alone. So some pre-packaged food will have to be eaten, likely sent to Mars ahead of the astronauts since it won’t all fit on board the spacecraft.

“If you think about having to produce food, stow it, and get it launched, the food they eat on the return trip will probably be five years old,” she said. To reduce the “ick factor,” NASA is also researching ways of producing packaged food so that it stays fresh, tasty, and full of nutrition for at least that long.

A manned trip to Mars is a technological wonder, as is being able to grow and eat vegetables in orbit. NASA will be growing the lettuce using a plant life-support system it calls VEGGIE. The technology makes it easy to grow edible plants in micro-gravity without using much power.

“When it comes to how long we can stay away from Earth, the problem’s not fuel, or oxygen, or water—it’s food,” said Mike Dixon, an environmental biology professor at the University of Guelph Ontario, Canada.

Dixon has worked with Russia and the European Space Agency to develop miniature, inflatable greenhouses in which large yields of food can be grown extra-terrestrially.

Dixon and other scientists have studied plant physiology, environmental sciences, and sensor technology in the Space and Advanced Life Support Agriculture Program at Guelph.

He told Healthline that Canada has been a world leader in this type of technology. “What’s the next worst place for growing plants after the moon? A snowbank in Canada.”

Dixon said tending to the plants also gives astronauts a tremendous psychological boost. “I just had dinner with an astronaut last night, and he said they fight over the plant experiments.”

Kloeris said Dixon is absolutely right. “The only thing that changed was that the plants, and our hair grew,” Kloeris said, speaking of her time in the isolation chamber. She added that staring at the same static walls becomes extremely monotonous aboard the International Space Station.

Plus, Dixon said, growing plants in space is just plain cool. “Imagine that first set of roses grown on the moon. Can you imagine the sexual favors you’d get for that?”