Yeast May Help Build Homes on Mars

Construction is a laborious process that requires specialized equipment, skills, time, and experience to accomplish. When researchers consider how to build on a planet like Mars, all of those aspects become even more complicated.

The Martian environment is vastly different from that of Earth, with surface temperatures ranging between -150°C and 20°C, and the whole planet having a fraction of the atmospheric pressure of Earth. While the planet has frozen water and plenty of rocks available as potential building materials, which have both been proposed to be used to make bricks, this process requires large amounts of heat, an energy-intensive resource not readily available on Mars.

Seeing this shortcoming, Jishen Qiu, a civil engineer at The Hong Kong University of Science and Technology, considered what materials and strategies may work under Martian conditions. The environment, he realized, was similar to that of the freeze-drying process. “My inspiration came from freeze-dried fruits that become harder,” he said in a press release.

In a study published in Chem Circularity, Qiu and his team built small, dome-shaped structures out of sand and a hydrogel mixed with yeast.¹ This biomaterial, after being exposed to conditions similar to Mars, was almost as strong as concrete and was more resistant to bending strain than this typical building compound.

To make a glue that would hold small particulates together, Qiu and his team considered incorporating yeast into their gelatin, creating a living material that would reinforce their scaffold.

The team genetically engineered Saccharomyces cerevisiae to express various adhesive proteins and mixed this with a gelatin to form a hydrogel. They added this hybrid glue to sand that represented Martian regolith, casted it into a mold, and allowed it to set at ambient room temperature for 30 minutes. With the help of the adhesive proteins on the yeast, the cells held the gel and particulate matter tightly together.

Then, they exposed their structure to Mars-like conditions: -30°C and 0.01 atmospheres of pressure. This caused the water in the hydrogel to freeze and then sublimate, mimicking what happens in freeze-drying. Curing under Martian conditions created a porous material that solidified the various attachments between yeast cells, gelatin, and sand particles.

Qiu’s team evaluated the mechanical properties of their hybrid biomaterial. Although the material was not as strong as concrete, it had more resistance to bending strain, suggesting that it would be better suited to hold up against strong winds and flying material on the Martian surface. Indeed, the stress on the material stayed below its maximum capacity even when the researchers exposed the structures to Mars-like wind and gravity.

The researchers also evaluated different yeast to gelatin ratios in their glue. The compressive strength of structures made with yeast included in the mix was 170 percent greater than structures made with gelatin alone. Adding the adhesive protein AGA2 further increased this strength. However, they found that other adherent systems, such as mussel foot proteins, which help mussels attach to rocks, offered limited improvements in overall function.

The researchers noted that their current study did not completely assess the energy costs or long-term maintenance of such a material. But the team is optimistic about the potential use of biomaterial as a viable option for construction on Mars.

“I always ask myself: Is there any physical law or fundamental mechanism that prevents us from doing this?” Qiu said. “I can’t see any at this point in time. We are confident in scaling it up. It would surprise me if materials for future Martian engineering will not be as diverse as those used in Earth engineering—and biology will certainly contribute.”