Space station biomining experiment demonstrates rare earth element extraction in microgravity and Mars gravity

Abstract

Microorganisms are employed to mine economically important elements from rocks, including the rare earth elements (REEs), used in electronic industries and alloy production. We carried out a mining experiment on the International Space Station to test hypotheses on the bioleaching of REEs from basaltic rock in microgravity and simulated Mars and Earth gravities using three microorganisms and a purposely designed biomining reactor. Sphingomonas desiccabilis enhanced mean leached concentrations of REEs compared to non-biological controls in all gravity conditions. No significant difference in final yields was observed between gravity conditions, showing the efficacy of the process under different gravity regimens. Bacillus subtilis exhibited a reduction in bioleaching efficacy and Cupriavidus metallidurans showed no difference compared to non-biological controls, showing the microbial specificity of the process, as on Earth. These data demonstrate the potential for space biomining and the principles of a reactor to advance human industry and mining beyond Earth.

Fig. 1. The BioRock Experimental Unit.

a Top-down image of one Experimental Container (EC) containing one EU (Experimental Unit) showing both culture chambers inflated with medium. b Sideways cross section through culture chamber showing location of basalt slide at the back of the chamber and principle of medium injection and inversion of membrane (shown here in yellow; left side closed, right side inflated with medium). c Image of basalt slide in a Petri dish submerged in 50% R2A in a ground experiment. d ESA astronaut Luca Parmitano inserts an EC into a KUBIK incubator on board the International Space Station (image credit to ESA).

Fig. 2. Bioleaching and control leaching of the most and least abundant rare earth elements.

Concentrations (ng in total chamber liquid) of rare earth elements (REEs) in each of the experimental flight and ground control samples at the end of the experiment (described in the text) for each of the three organisms and non-biological controls. The three most (Ce, Nd, La) and least (Tm, Lu, Tb) abundant REEs are shown here (all others in Supplemental Fig. 1). ISS shows the International Space Station flight experiments. Circles show triplicate measurements (n = 3 biologically independent samples. One non-biological microgravity and non-biological ground control sample were lost and are not shown) and the mean is given as a triangle. Error bars represent standard deviations.

Fig. 3. Effects of microorganisms on rare earth element leaching.

a Relative (%) difference in mean concentration of leached REEs in the bulk fluid between biological experiments and non-biological controls showing microgravity, simulated Mars and Earth gravities on the International Space Station for the three microorganisms. b Ground (true Earth gravity control) experiment for the three microorganisms. Standard deviations reported in Supplemental Table 3, statistics reported in the main text.