offbeat

Low-energy 3D printing could turn Martian dirt into sturdy structures

If humans ever make it to Mars - and that’s still a big IF - they will need to build shelters there. And they could build those shelters out of yeast and gelatin, if a method described by Hong Kong-based researchers makes it out of the lab. 

A paper published on Thursday by a group of researchers from The Hong Kong University of Science and Technology and The Hong Kong Polytechnic University describes a method for building structures on Mars that doesn’t rely on energy-intensive heating to turn regolith into building blocks. The team instead turned to bioengineered yeast and gelatin mixed with simulated Mars dirt to 3D print structures.

"My inspiration came from freeze-dried fruits that become harder,” senior author Jishen Qiu, an associate professor at The Hong Kong University of Science and Technology, told Cell Press, the publisher of the paper. 

Qiu’s idea is a relatively simple one once you break it down: Take one part yeast bioengineered to produce adhesive proteins that bind the components. Combine with artificial gelatin hydrosol to serve as a growth medium for the yeast. Add plain old Martian dirt, and extrude the material through a 3D-printing nozzle. 

If everything works as intended, the recipe should create a foamy substance that, when exposed to the dry, cold Martian atmosphere, essentially freeze-dries. As the ice sublimates into vapor, you should be left with a light, porous, but incredibly strong material. According to the researchers, that’s exactly what they got. 

“The hardened material achieved mean compressive and flexural strengths of approximately 12 and 6 MPa, respectively,” the team said. For reference, that’s roughly the same strength as low-grade terrestrial concrete. As an added perk, the team noted, the energy demand is one to two orders of magnitude lower than that of heat-processing Martian (or lunar, for that matter) dirt into building material.

According to the paper, the material can be broken down and reused too - provided at least a single yeast cell survives the process, and the cold, barren wasteland of Mars, that is. The team isn’t sure that would necessarily be the case, but nothing is stopping Martian yeast masters from keeping a supply on hand for future projects just in case. 

The structures they built and tested in their simulated Martian conditions were tiny little beehive-shaped things, measuring just 45 mm tall (a little under 2 inches). 

“Is there any physical law or fundamental mechanism that prevents us from doing this?" Qiu asks of his work. "I can't see any at this point in time.” 

Qiu said his team is confident that it can scale the tech, but that’s not the only thing that needs to be tested more fully. Per the paper, testing the ability of the yeast-gelatin building foam to retain the pressure necessary to keep humans from succumbing to the Martian elements was outside the scope of the research. 

“A practical lunar or Martian habitat must integrate pressure retention, gas tightness, mechanical support, thermal regulation, radiation shielding, dust protection, repairability, and resource recycling,” the paper notes. “These requirements will likely require hybrid architectures” that include both the yeast foam and more traditional structures. 

Either way, avoiding the need to heat Martian dirt could reduce the energy and heavy equipment required to build structures there. That’ll be important if we ever actually want to get to Mars. But if we get there, at least we’ll have yeast. ®