Can we grow veggies on Mars? Fly larvae and synthetic soil may hold the answer

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English peas grow in simulated Martian dirt. Emmanuel Mendoza hide caption

English peas grow in simulated Martian dirt.

Humans have stepped foot on the moon, but we haven't made it to Mars. Yet.

Amid the myriad barriers, a key issue to sending a crew to Mars is food. Weight, volume and longevity limit the kinds – and how much of it – can be brought on the long journey.

It's a challenge aerospace engineering undergraduate Emmanuel Mendoza has taken on. Specifically, growing our own food in the farthest reaches of the galaxy.

"What can we do with Martian soil, what modifications – if any – can we make to the soil in the future to, you know, make it more habitable for terrestrial plant growth on a different planet," he told NPR. "So I guess, it's extra-terrestrial plant growth."

Mendoza is currently running a study at Texas A&M University, where he's mixing simulated Martian soil and poop from fly larvae to find just the right recipe for growing plants on Mars.

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The seed of this idea was planted when Mendoza was in middle school, watching Ridley Scott's 2015 film The Martian, in which the fictional botanist Mark Watney becomes stranded on the inhospitable planet and grows potatoes to survive.

"That got me really interested in ... what nutrients or even just what soil structure does [Martian soil] have that we could potentially take advantage of," Mendoza said.

Now, he's running an experiment growing English peas in simulated Martian soil at the Forensic Laboratory for Investigative Entomological Sciences (FLIES).

"[This] Martian soil is manufactured on Earth. It uses data from Martian landers, and it's kind of expensive on a per-kilogram unit basis," Mendoza said, which limited the types of plants he could grow.

"I definitely considered potatoes [like Mark Watney]," he said. "The big reason I didn't grow potatoes were budgetary constraints and also just the fact that I couldn't necessarily get the data I wanted out of them."

Mendoza chose the peas because he could gather data on their growth. Emmanuel Mendoza hide caption

He wanted to be able to measure plant growth as it occurred throughout his experiment. Since potatoes grow underground, he'd only be able to collect data once they were done growing. In the end, Mendoza chose to grow English peas because they're self-pollinating, grow fairly quickly and he can see the shoots climb.

Martian soil — or regolith — isn't exactly ideal for plants from Earth. It tends to be rocky and coarse, and lacks the right organic matter.

"It's obviously missing the natural biota of any soil you'll find on Earth," Mendoza said. "And it's also missing some certain macronutrients that contain nitrogen, phosphorus and sulfur."

At the same time, it does contain other essential nutrients. "And so, it has an interesting balance – it has some elements that we need, and it's just missing other additives that come with having life for a significant amount of time," Mendoza said.

Here's where the larvae come in.

In order to supplement his simulated soil with those missing nutrients and organic matter, Mendoza turned to the larvae of black soldier flies, which excrete a powdery waste known as frass.

"They can break down almost any biomatter and they can turn it into really useful byproducts," Mendoza said. "And then you can use black soldier fly larvae frass as a nutrient substitute for soil."