As a product designer imagines a Martian boot made out of human sweat and fungus, her quest sparks a new question: can biomaterials open the door for a human colony on Mars?

In 2016, designer Liz Ciokajlo received a commission from the Museum of Modern Art (Moma) in New York: revisit the Moon Boot, a fluffy-looking snowshoe inspired by the footwear used by the Apollo astronauts.

Launched in 1972 at the height of the lunar missions, the Moon Boot is an icon of the 20th Century’s ‘plastic age’ and the museum curators wanted a new take on it.

Ciokajlo set out to reimagine it. She knew only a biomaterial would work in a post-plastic age, but the designer also wanted a new destination to inspire it. Our generation’s space travel obsession is not the Moon, she thought, but the red planet - Mars. And Mars allows you to really think outside of the box.

“Mars has always been a place where you can dream,” Ciokajlo says. “It is a place where you can reimagine how to live on Earth.”

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The final design can be manufactured with almost only human sweat and a few fungus spores, ideal for a seven-month trip to Mars with limited check-in luggage

The commission lead her to a wondrous biomaterial that had already attracted the attention of engineers innovating in building materials and of top space agencies like Nasa and the European Space Agency (Esa). Her final design, a tall, female, rough-looking boot, can be manufactured on board a spaceship with almost only human sweat and a few fungus spores, ideal for a seven-month trip to Mars with limited check-in luggage.

This magic biomaterial is mycelium, the vegetative part of the fungus. If you imagine that mushrooms are the ‘fruits’ of the fungus, mycelium could be regarded as its roots or stems. It looks like a mass of white thread-like structures, each called hyphae, which crisscross soil and other material in which fungi grows. Collectively, these threads are called mycelium and are the largest part of the fungus.  

Mycelium has amazing properties. It is a great recycler, as it feeds off a substrate (like sawdust or agricultural waste) to create more material, and has the potential of almost limitless growth in the right conditions. It can endure more pressure than conventional concrete without breaking, is a known insulator and fire-retardant and could even provide radiation protection on space missions. 

On Earth it’s currently used to create ceiling panels, leather, packaging materials and building materials, but in outer space it stands out for its architectural potential, says artist and engineer Maurizio Montalti, who has teamed up with Ciokajlo.  

“You rely on the cells capacity to replicate themselves, thus creating more material in short time,” says Montalti.

For her revisited boot, Ciokajlo wanted to use the human body as the source for some of the building materials and decided to employ sweat. Reusing perspiration is not entirely new in space exploration (the International Space Station currently reuses astronauts’ urine and sweat for drinkable water) but a novelty approach for footwear. She thinks it might make astronauts feel closer to home during the long journey to Mars.  

Mycelium materials can take shape in several ways

Mycelium’s adventures in space go beyond material innovation. As she researched the commission, Ciokajlo came across a feminist novel from 1893 that imagined Mars as a planet where gender roles reversed – which is why their creation is a boot for women. The novel propelled her to imagine a new society where biomaterials provide a new way to interact with our surroundings. Even the boot’s name, Caskia, comes from the novel: it is the planet’s only region with equal standing between men and women.

The design is still hypothetical, because the real boot submitted for Moma – and currently in display at the London Design Museum – did use mycelium but not human sweat, as their deadline was too tight, but the science checks out. 

Mycelium materials can take shape in several ways. If you have solid waste (like sawdust), you want to sterilise it and add the fungus so its spread can start. By incubating it in controlled conditions for temperature and humidity, the white veiny hyphae would compact to create a fibrous solid material. This is how Nasa and Esa hope to use mycelium for their Mars bases.

For Caskia, a special type of fungus (there are more than five million species) would feed off the nutrients diluted in human sweat after it is filtered for impurities. The ‘wet material’, as Montalti calls it, would be shaped with a mould directly around the astronaut’s feet and kept fed by sweat production.

In both methods, the fungus growth can be stopped by heating to up to 70 or 80C (F), which means either using an oven on Earth or exposing the culture to high temperatures on Mars or outer space.  

The substrate would possibly need an additional nutritional supplement to promote its growth, acknowledges Moltalti, but it is rooted in current mycelium science. The boot they created for MoMA used a special diluted formula.

“For each of our cultural inspirations you could find scientists that back this up,” says Ciokajlo.

The European Space Agency (Esa) is likewise pushing boundaries with mycelium. In a joint project with Montalti and the University of Utrecht, the agency is exploring whether fungi could be used to grow buildings, like labs and other facilities, in space

Launching from Earth with a fully formed Mars facility is expensive, with payload prices ranging at $10,000 (£7,700) per pound. Mining in Mars is also problematic and costly. Add that to the ever-present question of how to manage waste in space, and mycelium’s ability to decompose and recycle starts to look very promising.

The team had provisional results in October and Montalti says they are encouraging (Esa is still double-checking them, so they are not yet public). The engineer dreams about combining mycelium with 3D printing or even genetic manipulation to have more options.

On our planet, many projects have used mycelium as a structural component

On the other side of the Atlantic, Nasa is also examining whether their Mars missions could grow surface structures on the planet itself. The Americans are considering producing on Earth a flexible plastic shell seeded with mycelium and then activating the fungal growth once in Mars. That way a thin film can become thick roof or walls in a matter of days or weeks. The building could be malleable: fungus growth stops when their feedstock is consumed, their ideal temperature is withdrawn or the mycelia is killed via heat, yet the dormant fungi can be reactivated into growth, if repairs are needed.

One of the most appealing aspects of mycelium in relation to space architecture is the capacity of certain fungi to express melanin, a biomolecule that can shield humans from cosmic radiation. Montalti and ESA tested this property as part of their project.

On our planet, many projects have used mycelium as a structural component. For instance, a collaboration between the Karlsruhe Institute of Technology (KIT) and the Swiss Federal Institute of Technology (ETH) used 3D printing to create a branching structure that can support a roof.

For many, mycelium provides a golden example of circular economy. Waste comes in as input for the mycelium and the resulting material is potentially biodegradable, just like wood.

“Currently our materials come from extraction,” says architect Adi Reza Nugroho, from the Indonesian firm MycoTech that provided the mycelium for ETH and KIT. “Now we want to have a closed-loop cycle.”

If Nasa and Esa’s experiments are successful, a small group of fungus spores could provide the starting point for a living, natural settlement on Mars. From a handful of spores, they could replicate and find dozens of uses for astronauts walking around the red planet.

And if Ciokajlo and Montalti have it their way, and these humans can spare a bit of their sweat, even the shoes on their feet will start life as a fungus.

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Diego Arguedas Ortiz is a science and climate change reporter. He is @arguedasortiz on Twitter.

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