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Building lunar outposts may become a reality as scientists explore using lunar regolith to construct habitats. Experts suggest that bricks made from moon dust could be pivotal in establishing these bases. A recent study, based on experiments with lunar regolith simulant, reveals a groundbreaking method: bacteria-based sealant could repair cracks in these lunar bricks, ensuring structural integrity for long-term lunar habitation.
Bacteria Could Seal Cracks in Moon Dust Bricks for Lunar Outposts
Constructing a base on the moon using indigenous lunar resources is crucial for minimizing mission expenses. Transporting substantial quantities of materials from Earth to the moon is prohibitively costly. Therefore, utilizing lunar regolith to produce bricks has emerged as a promising solution. Numerous research teams globally, including those at the Indian Institute of Science (IISc), are actively experimenting with creating such bricks using lunar regolith simulants.
Understanding Lunar Regolith and Simulants
Regolith, in essence, is the loose layer of dust and fragmented rock covering the lunar surface. Due to the scarcity and value of actual lunar regolith samples, simulants – designed to mimic various regolith types – are employed in experimental studies. Previously, IISc researchers pioneered a technique utilizing a terrestrial soil bacterium, Sporosarcina pasteurii, to fabricate bricks from regolith simulant. This bacterium can convert urea, a metabolic byproduct, and calcium into calcium carbonate crystals. When combined with guar gum, extracted from guar beans, these crystals effectively bind regolith particles, solidifying them into bricks.
Sintering Lunar Bricks: An Alternative Approach
Subsequently, the same research group explored sintering for lunar brick production. This method involves heating a compacted mixture of regolith simulant and polyvinyl alcohol, a water-soluble polymer, to extreme temperatures within a furnace. Sintered bricks exhibited even greater strength than those produced using bacteria. However, the harsh environmental conditions on the moon present significant challenges.
Challenges of Lunar Environment on Construction Materials
Lunar bricks deployed in the vacuum of space must endure drastic temperature variations, ranging from scorching highs of 250 degrees Fahrenheit (121 degrees Celsius) to frigid lows of -208 degrees Fahrenheit (–133 degrees Celsius) throughout a lunar day. This extreme temperature fluctuation induces substantial thermal stress. Furthermore, the bricks would face constant bombardment from micrometeoroids and cosmic radiation.
“Temperature variations can be considerably more pronounced on the lunar surface, potentially causing significant long-term effects,” noted Koushik Viswanathan, from the IISc’s Department of Mechanical Engineering, in a press statement. “Sintered bricks are inherently brittle. The propagation of even a small crack could lead to rapid structural failure.”
Bacteria-Based Sealant for Lunar Brick Repair
Therefore, the capacity to effectively repair damaged bricks on the moon is paramount to prevent the collapse of a lunar outpost. Viswanathan and his team revisited their earlier concept of using Sporosarcina pasteurii, not for brick fabrication, but for developing a sealant to mend cracks and gaps in the bricks.
The researchers sintered bricks from regolith simulant and then deliberately inflicted various forms of damage – holes, V-shaped fissures, and semi-circular notches – simulating structural fatigue. Subsequently, they applied a slurry mixture, composed of Sporosarcina pasteurii, guar gum, and regolith simulant, onto the damaged bricks. They allowed the slurry to permeate the bricks over several days, filling the imperfections.
Self-Healing Properties and Compressive Strength
The bacteria performed two essential functions:
- Production of calcium carbonate, which effectively filled the cracks.
- Secretion of biopolymers, enabling the mixture to bond with the brick, resulting in resolidification.
The team observed that this process restored 28 to 54% of a brick’s original compressive strength; however, complete restoration to pristine strength was not achieved.
“Initially, we were uncertain whether the bacteria would adhere to the sintered brick,” stated Aloke Kumar of IISc. “However, we discovered that the bacteria not only solidify the slurry but also establish a strong bond with the existing brick material.”
Extraterrestrial Conditions and Future Research
While these results are promising in a laboratory setting, the lunar environment poses unique challenges.
“A critical question concerns the behavior of these bacteria under extraterrestrial conditions,” Kumar elaborated. “Will their properties alter? Will they cease carbonate production? These aspects remain to be investigated.”
To address these uncertainties, the team intends to send a Sporosarcina pasteurii sample into space on the upcoming Gaganyaan mission, India’s first crewed spaceflight, scheduled to carry three astronauts beyond Earth as early as 2026.
Gaganyaan Mission to Test Bacteria in Space
“If realized, this would be the first experiment of its kind involving this specific type of bacteria,” Viswanathan concluded.
The findings of this research were published on March 27 in the journal Frontiers in Space Technologies.