Bengaluru:

NASA’s Artemis program aims to establish a permanent presence on the Moon, and as part of this effort, astronauts will need to build habitats using materials sourced from the lunar surface rather than transporting resources from Earth. The Moon’s surface is rich in a material called regolith (Lunar soil), a mixture of broken minerals and rocks, which scientists have found can be used to create bricks.

As humanity moves closer to the goal of establishing permanent colonies on the Moon and Mars, the need for innovative solutions to overcome the challenges of extraterrestrial living grows more urgent. One such groundbreaking approach comes from researchers at the Indian Institute of Science (IISc), who have developed a bacteria-based technique to repair bricks that could one day be used to build habitats on the lunar surface—bricks that may suffer damage from the Moon's extreme environment.

The power of Sporosarcina Pasteurii:

 IISc researchers have harnessed the power of Sporosarcina pasteurii, a soil bacterium, to bind lunar and Martian soil simulants into brick-like structures. By converting urea and calcium into calcium carbonate crystals, these bacteria, in combination with guar gum, create a natural adhesive that binds soil particles together, forming eco-friendly bricks—a cost-effective alternative to conventional cement.

Building on this, the team also explored a method called sintering, which involves heating a mixture of soil simulants and polyvinyl alcohol to high temperatures, creating bricks of high strength suitable for housing. Sintering is scalable, allowing multiple bricks to be produced in a furnace.

Challenges of the harsh lunar environment:

To address this challenge, the researchers returned to Sporosarcina pasteurii. By introducing artificial defects into the sintered bricks and applying a slurry made from the bacterium, lunar soil simulant, and guar gum, the bacteria went to work, producing calcium carbonate to fill and heal the cracks. Over the course of several days, this slurry solidified, gradually restoring the bricks’ strength. While not as hard as the original sintered bricks, this process provided a way to repair damaged materials, extending the life of the structures built on the Moon.

Koushik Vishwanathan, co-author of the study and Associate Professor, Dept of Mechanical Engineering at the Indian Institute of Science (IISc), in an interview with ETV Bharat representative, said that these bricks, though strong, are not immune to the harsh lunar environment. With temperature fluctuations ranging from 121°C during the day to -133°C at night, combined with the constant bombardment from solar winds and meteorites, these bricks are prone to cracking, potentially weakening the structures built from them.

Aloke Kumar, an Associate Professor at IISc and co-author of the research study, highlighted the inspiration behind this research. After returning to India in 2017, he was struck by the challenges posed by extended space missions, especially with the Gaganyaan human space program on the horizon. Kumar, a mechanical engineer with experience working as a professor in Canada, recognised the need for innovative technologies to support astronauts during prolonged stays in space.

"Bricks, the fundamental building blocks of any house on Earth, would be equally essential for structures on the Moon. I wondered how we could make bricks in space using the resources available there," Kumar said.

Microbes: A natural ally for space missions

The idea is simple: These kinds of microbes present in soil on Earth play a significant role in maintaining soil ecology. The bacteria can form highly resistant, resilient spores that can survive for extended periods in harsh environments. According to Kumar, these bacteria could also play a role in supporting plant growth on lunar or Martian soil, potentially helping future astronauts grow food in space.

The natural process of Sporosarcina pasteurii converting urea into calcium carbonate fascinated him, sparking the idea of using this bacterium to help astronauts build and repair structures on the Moon. He said, "I am also trying to find why it happens, and why these bacteria evolve in the first place is still a subject of research for me."

"These spores are like seeds, and they can remain dormant for a long time," Kumar explained. By mixing these spores, which look like white powder, with lunar soil, the bacteria can remain viable and begin their work over time. By giving the example of making curd through bacteria, Kumar said that these bacteria grow automatically. This technique offers significant advantages—space transportation of large quantities of bacteria is unnecessary since they can be cultured in small amounts, making it an efficient solution for lunar missions.

Kumar elaborated on the process: "We’ve been researching brick-making on the Moon and Mars for about five years now. Using lunar soil simulants and a technology called sintering, we can create bricks at temperatures exceeding 1000°C. The soil particles slowly melt, and when the melted soil is put in a mould, it forms the sintered bricks through the process of thermal centric process. However, these sintered bricks are brittle and prone to cracking, which is a challenge in the harsh lunar environment. On Earth, this bacterium exists in the soil as a good bacterium that hydrolyses urea to form calcium carbonate, given the right circumstances. To repair them, we mix Sporosarcina pasteurii with lunar soil to form a slurry that, over time, solidifies and fills the cracks, providing a self-healing solution."

This technique, Kumar noted, has the potential to reduce the need for replacing damaged bricks, making structures more resilient and longer-lasting.

The bacteria also produce biopolymers that act as adhesives, binding soil particles together and reinforcing the structure of the brick, allowing the repaired bricks to withstand temperatures ranging from 100°C to 175°C—conditions that would typically weaken sintered bricks. The team was initially uncertain if the bacteria could adhere to the sintered bricks, but their success in solidifying the slurry and reinforcing the structure has opened up new possibilities for extraterrestrial construction.

Testing bacteria in space:

The researchers are now working on a proposal to send a sample of Sporosarcina pasteurii into space as part of India's Gaganyaan mission, where the bacteria's behavior in microgravity will be tested. As Vishwanathan and Kumar noted, "This will be the first experiment of its kind with these bacteria in space, and it raises fascinating questions about how they will behave in extraterrestrial conditions. Will they continue to produce calcium carbonate? Will their nature change? These are still unknowns, but we're excited to find out."

This pioneering work is not just about building structures on the Moon. The possibilities are vast, and the research at IISc is a critical step toward making extraterrestrial colonization a reality—one brick at a time.

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