The Promise of Lunar Construction

Establishing a permanent base on the Moon presents significant logistical challenges, particularly concerning the transportation of building materials. Shipping resources from Earth is prohibitively expensive, making the utilization of local lunar resources a critical necessity. Lunar regolith, the loose dust and rock covering the Moon’s surface, has long been considered a viable material for brick production. Multiple research teams globally, including those at the Indian Institute of Science (IISC), are actively exploring methods to create durable bricks from simulated lunar regolith.

Bacteria to the Rescue: A Novel Approach to Crack Repair

A recent study highlights a promising solution to a major challenge in lunar construction: repairing cracks in regolith bricks. Researchers have demonstrated that bacteria can effectively seal fissures in these bricks, perhaps extending the lifespan of lunar structures.

Previously, the IISC team pioneered a method using the soil bacterium *sporosarcina pasteurii* to create bricks from simulated regolith. This bacterium converts urea (a waste product) and calcium into calcium carbonate crystals. When combined wiht guar gum (derived from guar beans), these crystals act as a binding agent, solidifying regolith particles into robust bricks.

The same team also experimented with sintering, a process involving heating a mixture of regolith and polyvinyl alcohol to extreme temperatures. While sintered bricks exhibited greater initial strength, they remained vulnerable to cracking under the harsh lunar conditions.

The Challenges of the Lunar Environment

Lunar bricks must withstand extreme temperature fluctuations, ranging from 121°C during the lunar day to -133°C during the lunar night. These temperature swings induce significant thermal stress. Furthermore, the bricks are constantly bombarded by micrometeorites and cosmic radiation.

Changes in temperature on the surface of the moon can be very extreme, and over time can have a big impact. The bricks of the syintering are fragile. If there are cracks and cracks are enlarged, the entire structure can collapse quickly.
Koushik Viswanathan, IISC Mechanical Engineering Department

Koushik Viswanathan from the IISC Mechanical Engineering Department emphasizes the critical need for self-repairing materials, stating that unchecked cracks could lead to rapid structural failure.

The Healing power of *Sporosarcina pasteurii*

To address this vulnerability, Viswanathan and his team revisited their initial concept of using *Sporosarcina pasteurii*, this time not as a brick-making agent, but as a natural adhesive to mend cracks and holes. The team inflicted various types of damage – holes, V-shaped notches, and semicircular notches – on sintered regolith bricks to simulate structural fatigue. They then applied a slurry consisting of *Sporosarcina pasteurii*, guar gum, and simulated regolith to the damaged areas, allowing the mixture to seep into the cracks.

The bacteria perform a dual function: first, they produce calcium carbonate, effectively filling the cracks; second, they generate a biopolymer that facilitates the fusion of the slurry with the existing brick, restoring its structural integrity. The team observed a 28% to 54% recovery in compressive strength, demonstrating the bacteria’s remarkable ability to repair damage.

We were initially not sure whether the bacteria could stick to the bricks of syintire. But it turns out bacteria are not only able to compact slurry, but can also stick well to the material.
Aloke Kumar, IISC

From Lab to Lunar Surface: Future research

While these laboratory results are encouraging, the team acknowledges the challenges of replicating these findings in the harsh lunar environment.

One of the big questions is about how the behavior of these bacteria is in space conditions. Will their nature change? Will they stop producing carbonate? Things like that are still unknown.
Aloke Kumar, IISC

To investigate these questions, the team plans to send *Sporosarcina pasteurii* samples into space as part of the Gaganyaan mission, India’s first crewed spaceflight, scheduled for 2026.This experiment will provide invaluable insights into the bacteria’s behavior under space conditions.

If triumphant, this will be the first experiment of its kind with this bacterium, paving the way for self-healing lunar structures and potentially revolutionizing space construction.