Aled Roberts was in his lab, coaxing proteins together to develop a synthetic spider silk, when he stumbled onto an unanticipated breakthrough. To test his own silk, he’d created what scientists call a “control.” It was a comparison sample, using a protein from cow’s blood that wasn’t supposed to work much at all. This cow silk wasn’t supposed to be nearly as sticky as anything spiders might produce.
“Surprisingly, we found it was really good at sticking together,” says Roberts, a research fellow at the University of Manchester.
Roberts knew immediately that this shocking finding was worth more research. And now, a year later, his team has developed something extraordinary, if ever-so-nauseating, from that work. They’ve proven that by mixing together regolith (the inorganic space dirt found on the Moon and Mars), and a common protein in human blood, we can produce concrete on other planets that’s as strong as most concrete made on Earth. Mix in urea—the most common component from urine, other than water—and that concrete gets even stronger.
Given that Roberts says it could cost upwards of $1 million to send a single brick to Mars, his research could offer a cost-effective alternative to building on foreign planets. But the even greater benefits could be right here on Earth.
The historical precedent of blood concrete
While the prospect of mixing blood into concrete may sound gross, Roberts later discovered that it’s hardly a new idea. The addition of pig and ox blood in mortar can be traced as far back as ancient China and was relatively common across Europe in the Middle Ages (and potentially hundreds of years after). Albumin protein—the specific type of protein from blood that offered so much stickiness in mortar—had been used as glue in other contexts as well. Albumin sourced from milk stuck together planes until WWII, and albumin from egg whites adhered gold leaf to stone in ancient Egypt. (Blood is no longer used to produce mortar today. But egg whites are still prized by bakers today to coat and stick doughs together).
Though blood is no longer used to produce mortar today, “the historical precedent goes to show it has been done,” says Roberts. “Modern society, I guess, just went crazy with oil and cement production. We can go back and look at how we used to do things, and with our modern understanding, improve them, and take them further.”
Why these animal proteins are so sticky is something Roberts has explored but not yet definitely concluded. In animal bodies, these proteins offer a predictable viscosity to their blood. But they also have lots of binding sites, which allow them to transport hormones and fatty acids around the body.
“Initially, we thought [the binding sites were] the mechanism,” says Roberts. “That might have something to do with it, but in our [further] investigation, we found the structure of the protein completely changed when it’s hardened.”
To create concrete, these proteins mix with silica (aka, glass and sand) in a wet form, just like typical cement-based concrete. But as the concrete dries and hardens, Roberts observed that the proteins unfold, changing their structure. Through this structural change, they produce hydrogen bonds—the same strong bond that holds together water and, yes, spider silk.
“We’re not sure why,” admits Roberts. “It might have something to do with blood clotting. This is the main protein in blood. So when it clots, [this protein] gets involved.”
So far, this all makes some sense. But how did Roberts ever get the idea to mix urea into his concrete? Two reasons. First, urea is easily available in space because it’s in urine. Secondly, urea is a molecule that naturally forms strong hydrogen bonds. So urea further feeds the mechanisms that made the blood-based concrete work.
How would this work in space?
While it might sound overwhelming for astronauts to mix together their own concrete on Mars—sourced from fluids from their own bodies, no less—the process would be practical, says Roberts, and rely on just a few simple pieces of machinery.
Astronauts would donate plasma a few days a week, just like people donate plasma on Earth. This process doesn’t require red or white blood cells, so it’s less taxing to recover from than general blood donation. A centrifuge is all that’s needed to extract the specific protein from the blood sample. Producing urea is even easier. Astronaut pee could be collected in a toilet, then centrifuged to source that component.
With these body-born materials in hand, they only need to be mixed into space dust. The bricks could harden outside on the planet surface, so no energy would need to be expended on heating, melting, or curing the material. Of course, none of this would matter if astronauts couldn’t produce a meaningful amount of material from their own efforts. By Roberts’s calculations, over the course of a 3-year mission, an astronaut could produce enough concrete to house themselves plus one other person. That means, at least on paper, this concrete could scale to produce a larger, sustainable Mars habitat.
Landing back on Earth
Producing cosmic concrete in space is the literal definition of a moonshot. However, the greater impact of Roberts’s research may be right here on Earth. Under his company Deakin, he’s investigating how his protein-infused concrete could be scaled to make concrete—the most common and environmentally disastrous material on Earth—more eco-friendly. Deakin wouldn’t need to source space regolith for this concrete to work; everyday sand could do the job instead. He’s currently seeking funding to take this research forward.
“Animal and human blood aren’t sustainable on a significant scale, but plants and seaweed could potentially be a source [of alternative proteins],” says Roberts. “Now that we understand the mechanism, we can use other proteins to investigate it.”