Experiments on board the ISS reveal that we could extract rare earths in microgravity using bacteria. This condition will be essential if we want to establish ourselves permanently in space. Details of the study are published in Nature Communications.
Mining payloads from Earth's gravity is extremely expensive. Count more than 1500 euros per kilogram of material for the cheapest option (SpaceX). However, in the context of a human space exploration project, the success of our ambitions will depend on our ability to find and draw the essential materials directly on site . We know, for example, that asteroids and the Moon offer rare earths that we might need. It remains to know how to extract them.
On Earth, different machines allow the extraction of these materials. However, all are designed and developed to work with Earth's gravity . However, we know that on the Moon, and even more so on asteroids, gravity is much weaker. Also, we must imagine other ways to exploit space resources.
With that in mind, scientists wondered if bacteria could help. After all, on Earth, these organisms are involved in the natural weathering of rocks, releasing the minerals they contain. This ability of bacteria to leach metals is already exploited to facilitate human mining operations (biomining).
A decade ago, a team led by the University of Edinburgh (Scotland) therefore developed a small device the size of a can of matches called a "biomining reactor" with the idea of being able to install it aboard the International Space Station. The objective was to study this process of bacterial leaching in space . In July 2019, eighteen of these "reactors" were finally shipped to the ISS.
As part of a study conducted over three weeks, the researchers then embedded in each of these small boxes a bacterial solution submerging a small piece of basalt , a type of volcanic rock abundant on the Moon. Several experiments were carried out (simulated Mars gravity, simulated Earth gravity and microgravity with three different bacterial species:Sphingomonas desiccabilis, Bacillus subtilis and Cupriavidus metallidurans ). A bacteria-free control solution was used as a reference.
The researchers found that there were no significant differences in the bacterial leaching performance of B. subtilis and C. metallidurans . On the other hand, S. desiccabilis has been shown to be very effective, releasing between 111.9% to 429.2% more rare earths (cerium and neodymium) from the basalt than the control solution depending on the degree of gravity.
“Our experiments support the scientific and technical feasibility of biologically enhanced elemental mining across the Solar System “, concludes astrobiologist Charles Cockell, of the University of Edinburgh. “While it is not economically viable to mine these elements in space and bring them back to Earth, space biomining could potentially support a self-sufficient human presence in space “.
