But gardening doesn’t just require a plot of land, a bit of water, a beam of sunlight. It also requires very animate ingredients: the insects, like black soldier flies, and microorganisms that keep these ecological systems in working order. A trip to Mars for a long-term stay, then, won’t just involve humans. It will also involve creeping, crawling carry-ons most people don’t think about when they envision brave explorers stepping foot on new worlds.
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Space travelers haven’t yet gone very far for very long.
“Currently, when you’re going into space, it’s more like going on a prolonged camping trip,” said Scott Parazynski, a former NASA astronaut who spent nearly two months in space. Astronauts bring freeze-dried food (and flavor enhancers like hot sauce). If they’re on the International Space Station, they might get to look at, but rarely consume, fresh greens from an experimental lettuce plot.
“It’s a far cry from the kitchen downstairs and the spice rack,” Dr. Parazynski said.
To stay for an extended time on the surface of Mars, though, astronauts won’t be able to rely on their space pantries. They’ll need Martian gardens. And Martian gardens will need a little help — maybe from black soldier fly larvae and their excretions.
“They’re very voracious eaters,” said Hellen Elissen a researcher at Wageningen University and Research in the Netherlands. “They eat almost anything.” And if you feed them well, they’ll make a lot of frass.
In the past five or 10 years scientists have started to use that frass — rich in nitrogen, potassium, phosphorous and also bacteria — as fertilizer. The material also contains chitin, from the insects’ bodies, and leftover organic matter. Dr. Elissen recently published a review article about how frass affects plants and soil, and one of her main takeaways was that the value of the insects’ waste coincides with the value of their food. Grass? Frass suffers. Give the larvae higher-energy food scraps? Jackpot.