Science

mars: IISc, Isro experts develop ‘space bricks’ for Mars

BENGALURU: In what holds the potential of aiding construction of future settlements on March — something multiple spacefaring countries have in their long-term plans — a team from the Indian Institute of Science (IISc) and isro has developed a scalable technique to make “space bricks” using Martian Simulant Soil (MSS).
The team led by Aloke Kumar, associate professor at IISc’s mechanical engineering department, has demonstrated that Microbial Induced Calcite Precipitation (MICP) — where, under right conditions, certain bacteria can precipitate calcium carbonate — can create bricks using MSS.
Apart from Aloke, the team consists of Rashmi Dikshit, Nitin Gupta and Koushik Viswanathan from the IISc, and Arjun Dey from Isro’s UR Rao Satellite Centre. All five members were also part of a larger team that developed “space bricks” using lunar simulant soil (LSS) in February 2018 — TOI was the first to report it.
In their latest findings published in “PLOS One”, the team has reported creation of bricks using both LSS and MSS. Aloke explained to TOI that they have used a “bacterial growth induced biocementation process” for manufacturing the bricks in an organic manner with minimal intervention.
What this means in layman’s terms: Bacteria are very versatile organisms and certain species are capable of bio-mineralisation — a process by which living organisms produce minerals to harden or stiffen existing tissues — which was exploited to make these bricks.
The team used one specific bacterium (Sporosarcina pasteurii), which was introduced into simulant soil, which then hardened. Under ideal conditions, the MSS, which is in powder form, slowly turns into a brick in 15-20 days of introducing the bacteria.
Just as they had done with LSS bricks, the team used guar gum, a naturally occurring polymer, as an additive to add strength to the bricks from MSS. Extracted from guar beans, guar gum, Aloke said, has thickening and stabilizing properties useful in food, feed, and industrial applications.
Challenges of Martian soil
While the team had learned most of what was needed to make bricks using MSS from their earlier project, there were challenges it had to overcome.
“The bacterium used is soil bacteria on Earth. It did well when we had used LSS, but Martian soil has a lot of iron which is toxic. It also has many other attributes, including other harmful chemicals, which make it difficult for microbes to flourish,” Rashmi said.
Aloke said some of these issues were pointed out by a paper published in the “International Journal of Astrobiology” by Hitesh G Changela and others.
Titled “Mars: new insights and unresolved questions”, the paper says: “… Biomineralization processes have been proposed as a means of cutting the construction costs on the Moon and Mars. More work is needed on the feasibility of the use of Mars dust and regolith for such a proposed in situ resource utilization, eg testing this process under Mars-like conditions.”
It added that one limitation may be the various salts that are known to inhibit or prevent microbial metabolism, including perchlorates and chaotropic salts, sulphate salts, and those that create multiple stresses and poly extreme conditions.
“The biggest finding was that Martian soil is not the same as the lunar soil, it is harsher on microbial life compared to lunar soil. We solved this by using nickel chloride which helped what’s called the Ureolytic cycle that this type of bacteria uses to counter the soil’s inherent harshness,” Aloke said.
Aside from this, from the time they developed the lunar brick, the team has been able to shift to a scalable casting-based manufacturing method which, apart from enabling production of multiple bricks simultaneously, also provides flexibility to produce a range of shapes, including hollow structures, according to Koushik Viswanathan, another author in the study.
The IISc team has already demonstrated these capabilities in their lab.

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