Abstract
As humans explore and settle in space, they will need to mine elements to support industries such as manufacturing and construction. In preparation for the establishment of permanent human settlements across the Solar System, we conducted the ESA BioRock experiment on board the International Space Station to investigate whether biological mining could be accomplished under extraterrestrial gravity conditions. We tested the hypothesis that the gravity (g) level influenced the efficacy with which biomining could be achieved from basalt, an abundant material on the Moon and Mars, by quantifying bioleaching by three different microorganisms under microgravity, simulated Mars and Earth gravitational conditions. One element of interest in mining is vanadium (V), which is added to steel to fabricate high strength, corrosion-resistant structural materials for buildings, transportation, tools and other applications. The results showed that Sphingomonas desiccabilis and Bacillus subtilis enhanced the leaching of vanadium under the three gravity conditions compared to sterile controls by 184.92 to 283.22%, respectively. Gravity did not have a significant effect on mean leaching, thus showing the potential for biomining on Solar System objects with diverse gravitational conditions. Our results demonstrate the potential to use microorganisms to conduct elemental mining and other bioindustrial processes in space locations with non-1 × g gravity. These same principles apply to extraterrestrial bioremediation and elemental recycling beyond Earth.
Highlights
To move permanently into space, we must be able to implement industrial processes that can support settlement, such as mining natural resources
This study investigated the use of microorganisms to extract elements from basalt rock, an abundant regolith material found on the Moon and Mars (Ruzicka et al, 2001; McSween et al, 2009; McMahon et al, 2013), under microgravity, simulated Mars and simulated Earth gravities on the International Space Station (ISS)
We investigated microgravity as the lowest gravity level possible in order to explore the effects of a lack of sedimentation on bioleaching, to understand the role of gravity in microbe-mineral interactions in general, and to gain insights into the plausibility of industrial biomining on asteroids and other low gravity planetary objects, in particular
Summary
To move permanently into space, we must be able to implement industrial processes that can support settlement, such as mining natural resources. Microorganisms are used in a variety of industrial processes on Earth (Taunton et al, 2000; Schulz et al, 2013; Druschel and Kappler, 2015; Kalev and Toor, 2018). Among the advantages of biomining are its affordability and environmental sustainability. It can reduce metal contamination and improve the recycling of elements from electrical waste (Jerez, 2017), or reduce the use of environmentally damaging toxic compounds such as cyanides (Hilson and Monhemius, 2006). One mechanism by which such organisms can biomine is through the release of chelating compounds that sequester the element of interest (Sukla and Panchanadikar, 1993; Bosecker, 1997; Rezza et al, 2001; Schippers et al, 2014; Reed et al, 2016)
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