Summary
Humanity has been reliant on bacteria for centuries. From fermentation and agriculture to making vaccines and genetic engineering, bacterial strains have found widespread industrial and lifestyle applications. In the near future, they could help make resilient bricks to buildhabitats on the Moon’s surface.
A team from India has developed a process reliant on bacteria to make stronger brick-like structures that can survive the harsh atmosphere of the moon. The approach is notable because it uses the lunar soil as the base material. Or in the words ofNASA, In-Situ Resource Utilization (ISRU).
Solving a Critical Problem
One of the biggest challenges in the quest to build a settlement for humanity away from Earth is hauling all the material and equipment to an extraterrestrial body.According to Jennifer Edmunson, acting Program Manager for NASA’s Centennial Challenges,flying from Earth to the Mooncan cost $1-1.12 million per kilogram of cargo.
NASA / Ben Smegelsky
To avoid that, NASA has actively explored in-situ ideas that can exploit the material locally available on the Moon, and even Mars. Building on that approach, a team of experts at the Indian Institute of Science (IISc) and the Indian Space Research Organization (ISRO) has developed a method to create what they refer to as “space bricks.”
The fundamental material used to make these bricks is lunar soil, combined with urine (as the source of urea) and guar bean, which is commonly grown in India and used to produce a food thickening powder called guar gum. This plant extract is used in powdered form as an additive to boost the material’s strength.
The Secret Sauce
This is where the bacteria, a species namedSporosarcina pasteurii, come into the picture. It combines the calcium and urea in the building material to create calcium carbonate crystals that fill the cracks developing in the brick over time. “The final product obtained after a few days of incubation was found to possess significant strength and machinability,” says the team.
Broadly, the process is called bio-cementation, while the repair process is known as Microbially Induced Calcium Carbonate Precipitation (MICP). As pera paper published in the Frontiers journal, the bacterial repair can extend the functional lifespan of lunar bricks on the lunar surface.
Interestingly, this won’t be the first time that urine, or the aforementioned bacterial species, has appeared in space research. Experts at theUniversity of Manchestercreated a material called AstroCrete that would essentially combine Martian soil with urine and astronaut blood. Interestingly, the biocomposite material turned out to be nearly as strong as concrete.
As far as the bacterial species goes, it’s a special one, and the strengthening properties of this bacterium have already been demonstrated with Earth-based projects. During aTED Talk, Magnus Larsson demonstrated an award-winning method of using bacteria to make solid dunes and prevent the expansion of the Sahara desert. Ginger Krieg Dosier, an assistant professor at the American University in Sharjah, has also developed amethodto produce biobricks using the same bacterial species, urine, and sand.
The core role ofSporosarcina pasteuriiis to produce calcium carbonate, which is deemed extremely compatible with the constituents of concrete. When cracks appear in concrete, the bacterial material triggers the formation of calcium carbonate to fill the cracks and seal them.
Ina separate paper published in the PLOS Journal, the team tested another bacterial species namedBacillus velezensis. It is approximately ten times more affordable, and during lab tests, it produced twice the amount of the crack-filling material.
The Power of Beans
Calcium supplements are recommended by doctors worldwide to boost the strength and growth of bones. In nature, calcium’s role in minerals isn’t too different. The teams at IISc and IIT began their work on space bricks with bacteria, urea, and calcium. The base material was lunar soil simulant (LSS), which is rich in silicon, carbon, oxygen, and aluminum.
The guar gum, extracted from guar beans, plays a crucial role in making the construction material due to its role as a polymer additive. In fact, as per the research paper published in theCeramics Internationaljournal, the organic gum increased the brick’s strength by nearly six times.
“In independent experiments performed under flask conditions, it was observed that guar gum accelerated both bacterial growth and MICP related activity,” says the research paper. Another impressive aspect of these space bricks is that they are quite machinable and allow free-form shaping to suit the construction needs.
A simple lathe is all that’s needed to shape the material, which opens the doors for easily making interlocked designs and reducing the hassle of specialized molds. The team is now looking forward to making larger bricks and scaling up the manufacturing process beyond labs. The focus ahead will be on making the bricks stronger so that they can brush off seismic activity on the lunar surface. Yes, themoon is full of surprises, and ‘moonquakes’ are one of them.
Interestingly, the same team is alsoworkingon a similar bacteria-driven strategy for making bricks using the Martian soil. The real challenge, of course, will be transporting the machinery that can harvest the lunar regolith and turn it into space bricks. Let’s hope the Artemis mission brings back the glory days ofmankind on the moonand opens the doors for long-term settlements.
