Tough microbes able to survive extreme environments on Earth could be the key to constructing buildings to allow humans to survive on Mars, according to a research paper.

A global research team has analyzed the prospects for biomineralization on Mars, a process in which bacteria, fungi, and microalgae can create minerals as part of their metabolism, offering a byproduct that could be useful to prospective Martian explorers by providing the raw materials needed to produce aggregates such as concrete.

With an extremely thin and mostly carbon dioxide atmosphere, air pressure less than 1 percent of Earth's, and temperatures ranging from -90°C up to 26°C, Mars might not be a hospitable place for most terrestrial life forms, but some microorganisms have been found to thrive in acidic lakes, volcanic soils, and deep caves.

Polytechnic University of Milan materials engineering postdoctoral researcher Shiva Khoshtinat and a multidisciplinary team focused on a partnership between two bacteria: Sporosarcina pasteurii – which makes calcium carbonate through the breakdown of urea – and Chroococcidiopsis, which can survive extreme environments, including simulated Martian conditions.

The researchers propose a system in which the two organisms work together. Chroococcidiopsis releases oxygen, which helps support Sporosarcina pasteurii and produces an extracellular polymeric substance that can protect the latter bacteria from damaging UV radiation on Mars. Meanwhile, Sporosarcina produces polymers that help create minerals the authors think might be able to bind the Martian soil – regolith – to produce a material similar to concrete.

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The plan is then to use this aggregate to 3D-print buildings on Mars, the process offering the added benefit of producing excess oxygen to support human life, while excess ammonia could be useful in growing food.

There are some snags, though. Detailed analysis of the regolith will be needed to see if the proposal works, and plans to return samples to Earth from Mars have been repeatedly delayed. Recent reports suggest the Mars Sample Return program lacks political support.

Even if the plan were revived, there would still be significant barriers to overcome. "Integration into life support systems for recycling waste gases, supplying oxygen, or generating construction materials requires comprehensive safety and reliability assessments," said the paper published in Frontiers in Microbiology.

"Without integrated, long-duration testing in analog or space environments, the pathway from concept to application remains highly speculative."

Other proposals to make useful materials from extra-terrestrial soils include the application of potato starch and a pinch of salt. ®