What will humans eat on Mars? Earthbound researchers are cultivating menu choices 

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Ed Guinan, a professor of astrophysics and planetary sciences at Villanova University, has been experimenting to see what could grow on Mars. (Courtesy of Ed Guinan)

Ed Guinan, a professor of astrophysics and planetary sciences at Villanova University, has been experimenting to see what could grow on Mars. (Courtesy of Ed Guinan)

This story is from The Pulse, a weekly health and science podcast.

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If or when humans get to the red planet, one of the next big questions is: What will they eat there? Would it even be possible to have a healthy, or hopefully tasty, diet on a planet that doesn’t resemble Earth?

In a corner of a greenhouse at Villanova University, in a leafy suburb of Philadelphia, Edward Guinan, a professor of astrophysics and planetary science, has been experimenting to see what could grow on Mars. He started this project as part of a class in 2017. The goal was to grow a variety of crops in conditions retrofitted to resemble Mars.

Trying to grow anything there comes with some limitations.

“Mars doesn’t have clouds. We have cloudy days and rainy days here; on Mars, you don’t have those,” Guinan explained. “So overall, you get about 60% of the total energy of light over the Martian year.”

It’s darker, it’s a lot colder, and Mars is also covered in something called regolith. This is a type of iron-rich dirt that gives it its signature red look —  but it’s also contaminated with perchlorates.

“They’re hazmat. And they’re on Martian soil anywhere from a 10th of a percent to 1%,” Guinan said. “People think they’re left over from the lakes and oceans that used to be there.”

Villanova professor Ed Guinan holds a handful of “Martian soil,” an approximation of material found on the surface of Mars. (Emma Lee/WHYY)

The research doesn’t use authentic Martian soil. No samples have been returned to Earth yet.  The soil has been studied remotely with the use of Mars rovers and Mars orbiters. NASA and Jet Propulsion Laboratory scientists have, however, developed something called Mars regolith simulants that can be purchased online. And, thanks to iron oxides, it’s still reddish.

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Guinan encouraged his students to think about those limitations when choosing their crops. He hoped they would choose options that loved shade with shallow roots. He wanted them to keep nutritional value in mind. Think kale, or chard, but his students had other plans. In 2017, they planted hops.

The students were happy to see the hops thrive, and they became a bit of an international sensation. You can probably imagine the headlines and craft brew puns when “Beer on Mars” hit. Though hops may have put Guinan’s project on the map, he said there were more interesting things happening. And besides, hops, “it’s worthless, except for beer, flavoring beer. It took over the whole roof of the greenhouse, we had to cut it down,” he said, laughing.

Ed Guinan and his student at his Mars greenhouse at Villanova University. (Courtesy of Ed Guinan)

All that attention led to new experiments. People from around the world sent ideas about which crops to plant next. Two suggestions that piqued interest were peanuts and Jerusalem artichokes.

“They both grow. Peanuts is a legume. It just needs a lot of light. But it was feasible, and the Jerusalem artichokes grew extremely well. We had pots of them. They were growing out of their containers,” Guinan said.

One student joining Guinan to push the experimentation further was Alicia Eglin. She got involved in the project as part of her classwork — she recently graduated with a degree in astrophysics and astronomy. Another plus, she’s interested in gardening.

Eglin turned her attention to hydroponics. She developed her own system for growing plants in a nutrient rich solution. She was also able to find a perfect solution to Guinan’s challenge, both nutritious and fast growing. Her success: dandelion greens.

“Not everyone is accustomed to eating them as a food source. They tend to think of dandelions more as a weed. But that was the first crop that I did, and it did the best in the hydroponic system. They grew really big,” Eglin said. “Dandelions are great, because you can eat the entire plant. When you’re on Mars, you want to minimize waste. So for dandelions, you can eat the roots, leaves, the flowers, and stems, everything. It has medicinal purposes, you can make dandelion wine, dandelion tea, and then the greens themselves are really good for you.”

The team came up with another idea, too: using the mighty earthworm to improve the Martian soil. Regolith, when wet, has the consistency of clay. “You can have the worms in the Martian regolith, which is really important because they can help to transform it from that sandy clay-like texture into an actual soil more similar to Earth through the introduction of organic matter, in the worm castings,” Eglin explained.

Another benefit of packing invertebrates for Mars is that they can be turned into a source of protein. “The likelihood of having cows or chickens or any traditional agricultural animals on Mars is really unlikely because you have to transport them there. And then feed them and all that other stuff when you’re trying to figure out how to feed the astronauts first,” Eglin said.

In fact, Guinan has already perfected his recipe for earthworm.

“I push the poop out of them. And then I just fried them like hell, until they looked almost crisp. A lot of garlic salt was my way. So I couldn’t taste anything, I’ll just taste it like french fries. It worked,” he said. “I didn’t get sick. I wouldn’t make it like an everyday meal. But I know on Mars, it’s a good source of protein.”

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