one creates cement, the other protects it

Mars has become an obsession. Missions like those led by SpaceX demonstrate this and the truth is that going is the “simple” part. The really difficult thing is terraforming the planet to be able to carry out long-term missions in the field. In the movie ‘The Martian‘We already saw how an astronaut survived on Mars based on field-grown potatoes and, although it may seem like science fiction, we are already making progress on it. But we also need to build, and it is best to use Martian dust to create bricks.

As? With the help of two bacteria.

Biofoundation. Both the Moon and Mars are covered in dust. This mantle is made up of a series of elements that we can use to our advantage to create construction materials. It is much easier to figure out how to transform these materials into something useful than to carry kilos and kilos of materials from Earth, and in a study published in Frontiers in Microbiology addresses that problem.

In it, researchers from the ‘Giulio Natta’ Department of Chemistry, Materials and Chemical Engineering of the Polytechnic of Milan describe the process of transforming Martian regolith into a concrete-like material through a process called biocementation. And the proposal is to use a duo of bacteria capable of carrying out this transformation.

‘Mason’ bacteria. The protagonists are the Sporosarcina pasteurii and the Choococcidiopsis and the key process of the technology is ‘Microbially Induced Calcium Carbonate Precipitation: a process by which microorganisms generate calcium carbonate at room temperature. In the case of the Sporosarcina pasteuriithe process is based on ureolysis.

Thus, the bacteria produces the enzyme ureasewhich hydrolyzes urea into ammonia and carbonic acid. When released, it raises the pH of the environment, while carbonic acid dissociates into carbonate ions. When they combine with calcium ions present in the medium, they precipitate as calcium carbonate crystals on the bacterial cell walls and on soil particles.

A confusing and technical explanation to say that they generate a waste that acts as a natural cement that joins the regolith particles Martian, transforming naturally loose dust into a compact material with compressive strengths similar to those of some concrete mixtures.

BIOMEX. On the other hand, there is the Choococcidiopsis. It is one of the most resistant organisms we know – like the friendly tardigrades -. They are capable of surviving in conditions that simulate the Martian environment and, in fact, a few years ago the mission BIOMEX of the European Space Agency demonstrated that strains of this bacteria exposed without any shield for 18 months to both the vacuum of space and solar radiation were intact. Once they were rehydrated, they resumed their metabolic activities.

This is important because we have already “proven” the Choococcidiopsis in space, and its role in this story is not because of its ability to convert regolith into concrete, the other one takes care of that, but because of its extreme resistance. What the researchers propose is an association between the two bacteria.

Through photosynthesis, the Choococcidiopsis releases oxygen that creates a favorable microenvironment for the Sporosarcina pasteurii Do your job while, in turn, providing favorable conditions for your companion’s survival in the hostile Martian environment.

Defensive arsenal. That is, while one works, the other provides food and defense. And, really, the defensive arsenal of the Choococcidiopsis It is imposing. As if it were the armor of a state-of-the-art tank, it has three lines of defense:

• The first is formed by extracellular polymeric substances that form a thick layer that filters almost 70% of UVA radiation, almost 70% of UVM radiation and almost 90% of UVC.
• The second line consists of antioxidants that bind to the outer membrane to act as a photoprotector, neutralizing the reactive oxygen species generated by radiation.
• And the third defense includes UV filters. As if that were not enough, Choococcidiopsis can self-repair its DNA if it is damaged by radiation.

Beyond construction. It is resistant and resilient, but before launching flying bells and bacteria to Mars, the team itself details that you have to go step by step. Although different agencies want to build the first human habitat on Mars in the 2040s, it is no longer just that building on the planet is a problem: the question of how these pioneers will return must be answered with guarantees.

There are plenty of projects underway to learn how to build and farm on Mars by imitating the planet’s characteristics.

At the moment, they are demonstrating that Martian material can be converted into construction material, but there is still a long way to go, such as replicating Martian conditions on Earth to optimize these construction processes. And discoveries such as the work of these bacteria together can lead not only to novelties in terms of construction, but also to potential uses of the capabilities of some of them to produce oxygen on Mars or even use the by-products they discard as an element for crops in space.

Ammonia, for example, which could be used as fertilizer for crops.

Images | T. Darienko, Interstellar Lab

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