Astrobiology: Mining with microbes in space

Microbes can extract economically important elements from rocks at zero gravity, reports a study in Nature Communications. These results suggest that ‘biomining’ by microbes could be a critical facet of settling on other planets.

Rare Earth elements (REEs) are critical components of electronics because of their unique magnetic or catalytic properties. However, they are challenging and expensive to mine, and demand will soon surpass supply. As humans look to explore other planets, efficient and simple means of extracting REEs will be critical. Microbes are used to mine REEs from rocks on Earth, but whether they could do this in low or zero gravity was unknown.

Charles Cockell and colleagues assessed the biomining potential of three species of bacteria (Sphingomonas desiccabilis, Bacillus subtilis and Cupriavidus metallidurans) at microgravity and simulated Mars gravity aboard the International Space Station. To do so, the authors measured the extraction efficiency of the bacteria — the amount of 14 different REEs that could be leached from basalt (analogous to much of the material on the surface of the Moon and Mars). Parallel experiments were conducted on Earth under normal gravity conditions. They found that S. desiccabilis was able to leach REEs from basalt at all three gravity conditions. Furthermore, this bacterium’s leaching efficiency was similar across the gravity levels tested, and was highest for REEs that are most abundant in basalt (approximately 70% extraction efficiency for Cerium and Neodymium). The other bacterial species that were tested showed either reductions in leaching efficiency in low gravity, or no ability to leach REEs under any of the experimental conditions.

These results underscore that although microbial biomining capabilities are organism-specific, they are possible in space and at Mars-like gravity.