As lunar exploration shifts toward permanent settlement, exemplified by NASA's Artemis initiative, reducing dependence on Earth-supplied building materials is crucial. Lunar regolith, a powdery mix of shattered minerals and rocks, offers a viable on-site alternative.
Previously, IISc engineers developed a method to produce bricks from regolith simulants using the bacterium Sporosarcina pasteurii. This microbe facilitates the formation of calcium carbonate by metabolizing urea and calcium in the presence of guar gum, effectively binding the soil into hardened structures. The resulting bio-bricks provide a cost-effective, sustainable substitute for cement.
The team also employed sintering, a traditional brick-making process involving high-temperature heating of compacted regolith mixed with polyvinyl alcohol. This technique yielded bricks of exceptional strength suitable for housing. "It makes bricks of very high strength, more than adequate even for regular housing," explained Aloke Kumar, Associate Professor at IISc and corresponding author. The scalable nature of sintering enables batch production in furnaces.
However, the lunar surface presents extreme conditions, with temperatures ranging between 121oC and -133oC, alongside continuous exposure to solar radiation and micrometeorite impacts. These factors can induce structural cracks in sintered bricks. "Sintered bricks are brittle. If you have a crack and it grows, the entire structure can quickly fall apart," noted co-author Koushik Viswanathan, also an Associate Professor at IISc.
To counteract this vulnerability, the researchers reintroduced S. pasteurii into the process. In a new study, they engineered flaws in sintered bricks and treated them with a slurry containing the bacterium, guar gum, and lunar soil simulant. Over several days, the bacteria generated calcium carbonate within the cracks and secreted adhesive biopolymers, effectively sealing the defects and restoring much of the bricks' original strength.
"We were initially not sure if the bacteria would bind to the sintered brick," said Kumar. "But we found that the bacteria can not only solidify the slurry but also adhere well to this other mass." Tests revealed that the repaired bricks could endure temperatures from 100oC to 175oC.
Kumar emphasized the need to understand how these microbes function beyond Earth: "One of the big questions is about the behaviour of these bacteria in extraterrestrial conditions... Will they stop doing [the carbonate production]? Those things are still unknown."
To address these uncertainties, the team is preparing to include S. pasteurii in an upcoming Gaganyaan mission to assess its growth and activity in microgravity. "If that happens, to our knowledge, it will be the first experiment of its kind with this type of bacteria," Viswanathan added.
Research Report:Bacterial bio-cementation can repair space bricks
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