Astronaut Blood, Urine Make Perfect Extraterrestrial Concrete

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One of the questions astronauts get asked the most revolves around bathroom procedures while in space—namely how do you do it and where does it go? Researchers at the University of Manchester may have just worked out a really interesting answer to that question if humans ever colonize the moon or Mars.

In a new study, scientists showed a protein from human blood, combined with a compound from urine, sweat or tears, creates a “glue” that can hold moon or Mars soil together in material that is stronger than ordinary Earth concrete. The team says the blood- and urine-derived material is perfectly suited for construction work in extra-terrestrial environments.

Human serum albumin (HSA) is the most abundant protein in human blood plasma, and is replenished at a high enough rate per day that extraction can occur multiple times per week, if needed. And given that the cost of transporting a single brick to Mars has been estimated at $2 million, the ability to utilize resources already on the Red Planet is sorely needed.

“Scientists have been trying to develop viable technologies to produce concrete-like materials on the surface of Mars, but we never stopped to think that the answer might be inside us all along,” said first author Aled Roberts, a research fellow at the University of Manchester.

At first, the research team used just HSA to act as a binder for simulated moon or Mars dust to produce the concrete-like material they named AstroCrete. The novel material demonstrated compressive strengths as high as 25 MPa (megapascals)—which is about the same as the 20 to 32 MPa seen in Earth-bound concrete.

The scientists found that the strength of the bond is based on how the blood proteins denature, but the mechanism behind the bond is “complex and has yet to be fully resolved, but likely involves a mixture of interactions including entanglement, ionic-, hydrophilic- and hydrophobic bonding.”

While blood is one bodily fluid readily available in space, the researchers quickly realized there is another—urine. The average person produces approximately 59 g of urine per day— more than half of which is urea, a powerful protein denaturant and biological waste product that is also excreted through sweat and tears.

When the team employed urea to help create AstroCrete, they saw a 300% increase in compressive strength. In fact, the best performing material had a compressive strength of almost 40 MPa, substantially stronger than ordinary concrete.

The researchers calculate that more than 500 kg of AstroCrete could be produced over the course of a 2-year mission to Mars by a crew of six astronauts. If used as a mortar for sandbags or bricks, each crew member could produce enough AstroCrete to expand the habitat to support an additional crew member, doubling the housing available with each successive mission.

As the researchers note in their paper published in Materials Today Bio, the strength of the novel material deserves further investigation including possible optimization techniques, but it is not without its challenges, such as the likely need for downstream processing, like purification methods.

Even if AstroCrete turns out unviable for extensive construction use in a future Martian colony, the scientists say understanding the potential uses and limitations of such materials could be the difference between life and death.

“The significant time delay between Earth and Mars, both in terms of logistical resupply (∼26 months) and communication (up to 44 minutes), means that the ability for astronauts to devise solutions to novel threats and implement emergency repairs with the resources at hand will be critical to mission safety,” they conclude in their paper. “The understanding that human blood plasma and urine, combined with [Mars dust], can form a strong material could potentially solve a life-threatening emergency.”

Photo: Moon and Mars bio-composites. Credit: Aled Roberts, Research Fellow, Future Biomanufacturing Research Hub, Manchester Institute of Biotechnology

 

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