Mars Perchlorate Transforms from Obstacle to Ally in Space Construction
In a groundbreaking discovery, scientists from the Indian Institute of Science (IISc) in Bengaluru have revealed that perchlorate, a chlorine-based compound long deemed hostile to life on Mars, may actually serve as an unexpected aid in constructing structures on the Red Planet. Collaborating with researchers from IISER-Kolkata and Isro astronaut Shubhanshu Shukla, the team has demonstrated that under specific conditions, perchlorate can enhance the strength of bacteria-produced "space bricks." This finding challenges previous assumptions and opens new avenues for sustainable building methods in extraterrestrial environments.
Rethinking Martian Chemistry and Biology
Perchlorates have been detected at multiple Martian landing sites and are known to stress living cells, interfering with microbial growth and posing health risks to humans. For years, scientists exploring biological construction routes on Mars viewed this compound as a significant constraint that needed to be eliminated or avoided. However, the new study, published in the journal PLOS One, highlights a more intricate interaction between chemistry, biology, and soil, suggesting that perchlorate's role is not purely detrimental.
Aloke Kumar, an associate professor in mechanical engineering at IISc and the corresponding author of the study, emphasizes the importance of this research. "Mars is an alien environment. Understanding the impact of this new environment on Earth organisms is a crucial scientific question," he says. The study shifts the narrative from viewing perchlorate as a mere obstacle to recognizing its potential benefits in specific contexts.
Biocementation and Bacterial Adaptation
The research team focused on bacteria capable of binding loose soil into solid blocks through a process called biocementation. In earlier work, IISc researchers had shown that the soil bacterium Sporosarcina pasteurii could produce calcium carbonate crystals that glue together particles of lunar or Martian soil simulants. This process requires urea, calcium, and guar gum, a natural polymer that supports bacterial survival.
In the latest study, the team used a more robust bacterial strain isolated from soils in Bengaluru. After confirming its mineral-forming ability, they examined its response to perchlorate levels comparable to those measured on Mars, reaching up to about one percent. In collaboration with IISER-Kolkata, Professor Punyasloke Bhadury's group analyzed how perchlorate alters cell behavior.
The findings revealed that bacteria exposed to perchlorate grew more slowly, became rounder in shape, and began clumping together, all clear indicators of chemical stress. Additionally, they released higher levels of proteins and other molecules into their surroundings, forming an extracellular matrix.
Surprising Strength in Stressed Conditions
When these stressed bacteria were introduced to synthetic Martian soil in laboratory settings, the results were unexpected. With guar gum and a small amount of nickel chloride present, the resulting bricks exhibited greater strength than those produced without perchlorate. Microscopy analysis showed more mineral precipitates and fine "microbridges" formed by the extracellular matrix, which linked bacterial cells to soil grains and minerals.
Swati Dubey, the study's first author from IISc, explains this paradoxical effect. "When studying perchlorate's impact on bacteria in isolation, it appears as a stressful factor. But in the bricks, with the right mixture ingredients, perchlorate actually helps enhance strength," she says. This insight underscores the complexity of biological and chemical interactions in extraterrestrial environments.
Implications for Sustainable Building on Mars and Earth
The ultimate goal of this research is to develop alternative, sustainable building strategies that reduce reliance on carbon-intensive cement-based processes, both on Earth and Mars. Co-author Shubhanshu Shukla, who is pursuing his Master's degree with Kumar at IISc, highlights the practical applications. "Such technologies can facilitate smoother future Mars landing missions by aiding in the construction of better roads, launch pads, and rover landing sites," he notes.
Shukla further elaborates on the concept of in situ resource utilization. "The idea is to maximize the use of local resources. We don't have to transport materials from Earth; instead, we can utilize available resources on Mars to build structures, making navigation and sustained missions over time much more feasible," he adds. This approach aligns with broader efforts in space exploration to minimize costs and environmental impact.
This study not only redefines the role of perchlorate in Martian environments but also paves the way for innovative construction techniques that could benefit both space exploration and terrestrial sustainability initiatives.
