Microscopic “buddies” with potential: Special bacteria could one day supply stations on foreign celestial bodies with rare raw materials, according to experiments on the International Space Station ISS. According to this, one of three of the tested bacterial species is able to mobilize rare earth metals from basalt material for extraction even in weightlessness and simulated Mars gravity.
You can apply the lever to the most stubborn materials: The biochemical capabilities of certain microorganisms are already being used intensively in various industrial and manufacturing processes – including in mining. In the process known as biomining, microbes catalyze the extraction of certain elements from rocks. The organisms can dissolve the substances from the ore by releasing substances that convert metals from bound forms into water-soluble salts. The desired substances can then be obtained without any problems from the solutions, which then seep out of the rocks contaminated with the microbes. The so-called rare earth metals, to which the lanthanoids, scandium and yttrium belong, are of particularly great economic interest. Because of their special properties, including ferromagnetism and luminescence, they are required for many high-tech applications.
What role does gravity play?
In this context, the scientists of the European space program “BioRock” are now looking at space. “Our experiments were supposed to sound out the feasibility of biologically improved element degradation in space. Although it is probably not economically feasible to break down these substances on alien celestial bodies and bring them to earth, space biomining could possibly support a self-sustaining human presence in space, ”explains project leader Charles Cockell from the University of Edinburgh. Specifically, it means stations or settlements on the moon or Mars.
The focus of their recently published study was the question of the extent to which bacteria, which are able to mobilize rare earth metals from rocks on earth, can also do so under changed gravity conditions. It is already known that certain behaviors and characteristics of some microbes are tied to gravity. This can be due to the changed distribution of nutrients or waste. As part of the BioRock project, astronauts carried out experiments on the ISS to clarify to what extent three types of bacteria are still capable of biomining rare earth metals in zero gravity and under simulated Mars conditions.
The microbes should be bothered by basalt. This terrestrial material corresponds to rocks that are typically found on the moon or Mars, the scientists explain. For the tests, basalt platelets were placed in special analyzers and soaked with nutrient solutions containing bacteria. The species Bacillus subtilis, Cupriavidus metallidurans and Sphingomonas desiccabilis were examined. Some of the analyzers were exposed to weightlessness on the ISS. Others, on the other hand, were centrifuged in order to use the centrifugal forces to simulate gravitational conditions such as those on Mars or Earth. After 21 days, the fluids were examined to check to what extent the microbes were able to mobilize 14 rare earth elements from the basalt.
Only one bacterium shows potential
The results of the analysis showed that only the bacterium Sphingomonas desiccabilis apparently coped with the changed gravity conditions without any problems. The scientists report that these microbes lead to the same final yields of the rare earth metals under all gravity conditions. With the other candidates, however, this was not the case: Bacillus subtilis delivered significantly lower yields with reduced gravity than under terrestrial conditions and Cupriavidus metallidurane could no longer mobilize any rare earth metals.
The investigation thus shows: Space biomining has potential, but only certain microscopic “buddies” are suitable for use with reduced gravity. As Cockell reports, there is already concrete potential for the supply of raw materials to a future lunar station: “The Oceanus-Procellarum region of the moon could represent a favorable target for the scientific and economic development of humans beyond the earth,” says the scientist. Because, according to him, there are rich rocks there, the rare earth elements of which could possibly be made available by biomining.
Source: University of Edinburgh, specialist article: Nature Communications, doi: 10.1038 / s41467-020-19276-w