An artist's rendition of a Martian town. [Credit: Lemberg Vector Studios | CC BY 2.0]
When Javier Fernandez models a Martian colony, there are a lot of shrimp involved. Together with a team of sustainable development engineers, he is pioneering a building material that could offer a solution to one of space exploration’s greatest challenges.
Sending stuff to space is ridiculously expensive. It costs about $10,000 to launch a single pound of cargo into orbit around Earth. That’s why heavy traditional building materials, such as concrete or steel, are impractical for off-Earth construction sites.
By blending chitin, a tough, flexible material found in shrimp shells and insect exoskeletons, with weak acid and imitation Martian soil, Fernandez and his Singapore-based team have created a new material called biolith. Their hope is that this substance may one day be manufactured right there on the red planet, with no imports required. Results from their test run were published in September 2020 in PLoS ONE.
Nature-based building is a hot topic in extraterrestrial construction. Biopolymers, the tough materials made by living cells, “are a very good way to go,” says Stanley Starr, a retired branch chief for the applied sciences at NASA. Other construction candidates have been crafted from algae, plants and even iron mined by bacteria.
So far, biolith shows a lot of promise and versatility. The substance looks basically like terra cotta when dry. But by tweaking the Mars dirt to acid to chitin ratio in biolith, it can be mixed for almost any application. “We demonstrated that the material can do everything from making buildings to cutting to sealing,” says Fernandez, “so we wouldn’t need to send a different material for every purpose.” In a pinch, the material can even be molded by hand.
Biolith’s main ingredient, chitin from recycled exoskeleton, is renewable. Based on the Singapore team’s proposal, as long as a few astronauts are willing to work the old arthropod farm, space agencies could save a fortune in shipping costs.
“The concept makes sense,” says Tony Muscatello, a research chemist who worked on Martian water management at NASA for more than a decade. “But it has some problems.”
One issue boils down, literally, to water. Raw biolith requires liquid water to keep the mixture pliable. However, “on Mars or on the moon, there’s not enough atmosphere for water to behave properly,” Muscatello says. In cold areas of these distant bodies, water freezes very quickly. Elsewhere, it instantly boils. This could make biolith tricky to produce on site.
Sadly, it also rules out the shrimp. They make a great prototype chitin source on Earth because their durable shells are a cheap and abundant waste product. But like Elton John’s kids, Mars ain’t the kind of place to raise shrimp.
Fernandez’s team, however, is considering an alternative. Black soldier flies, also chitin-rich, require less water and could work a double shift: construction and waste management. Young flies thrive in human feces, which they convert into compost. Upon fulfilling their poopy purpose, the insects would be harvested and recycled into chitin, destined for an afterlife as a wall strut.
One thing is for certain: whatever Martian homes are made of — be it bugs, seafood, algae or iron — their manufacturing process must be part of a sustainable system. That means carefully recycling every scrap of metal, every shred of carbon and every drop of water. “You’ve got to be able to close all the ecological loops,” Starr says.
Fernandez agrees. “There is no other way.”