Biomining of Lunar-Relevant Materials under Simulated Lunar Gravity on the International Space Station

With near-future manned space exploration expanding beyond low Earth orbit out toward the Moon and beyond, there is a critical need to understand how a sustained human lunar presence can be supported through in-situ resource utilization (ISRU), as transporting supplies to the lunar surface remains technically challenging and costly(Y. Gumulya et al., Minerals Engineering, 2022; R. Santomartino et al., Nature Communications, 2023). Biomining, a terrestrial biotechnology that employs microorganisms to mobilize useful elements from rock, represents a promising approach for space-based ISRU. Recent biomining experiments aboard the International Space Station (ISS), including BioRock using Martian rock analogs and BioAsteroid using meteoritic material, have demonstrated that microbial mobilization of economically and ISRU-relevant elements is feasible in space(C. S. Cockell et al., Nature Communications, 2020; R. Santomartino et al., in review). However, biomining of lunar(-like) material, particularly under lunar-like gravitational conditions, has not yet been explored. For lunar-specific biomining, heterotrophic organisms might be more suitable than chemolithotroph ones, due to their capacity to bioleach silicon-rich minerals. The use of cyanobacterial biomass as a reusable “nutrient cartridge” to support their organics requirement in space represents a key but untested component of closed-loop ISRU systems (R. Santomartino et al., Nature Communications, 2023; C. Verseux et al., Frontiers in Microbiology, 2021).

Here, we propose an ISS experiment to investigate biomining of lunar KREEP-like material under multiple gravity regimes. The primary objectives are to (1) quantify biomining performance on lunar(-like) substrates under simulated lunar gravity, (2) compare biomining efficiency across multiple gravitational conditions, (3) test whether cyanobacterial biomass enhances biomining performance, and (4) demonstrate metabolic coupling between autotrophic biomass and heterotrophic microorganisms under lunar-relevant gravity. The experiment will employ flight-proven bioreactor hardware containing Sphingomonas desiccabilis, a microorganism previously shown to biomine rock under spaceflight conditions, partially supplied with stable isotope-labelled biomass derived from Anabaena cylindrica. Biomass from this cyanobacterium, which is being studied for its ability to grow from resources available on the Moon or Mars, has previously been demonstrated to support the heterotrophic growth of other organisms.

Incubations will be conducted within the existing KUBIK facility aboard the ISS, which provides controlled temperature conditions and simulated gravity environments. Following sample return to Earth, a combination of microbiological, chemical, isotopic, and geological analyses will be performed to assess microbial activity, element mobilization, and metabolic coupling. Multiple gravity regimes, along with Earth-based ground controls, will allow direct evaluation of gravitational effects on biomining efficiency and microbial physiology.

We expect to observe measurable mobilization of rare earth and other ISRU-relevant elements from the mineral substrate, as well as isotopic signatures indicating utilization of cyanobacterial biomass by S. desiccabilis. Differences in metal-leaching efficiency and microbial responses across gravity conditions are anticipated. This experiment will provide the first proof-of-concept demonstration of biologically mediated loop-closure relevant to lunar ISRU, informing future strategies for sustainable lunar exploration and advancing our understanding of microbe-mineral interactions beyond Earth.