Abstract EANA2025-173

REE are essential for advanced technologies, including space exploration, making their sustainable extraction a strategic priority for future missions. This study integrates findings from experimental and field research on the microbial mobilisation of REE in terrestrial Mars analogue environments, articulating their potential applications in space exploration and in-situ resource utilisation (ISRU) in astrobiological contexts. This multidisciplinary study combines microbiological, geochemical and mineralogical characterisation of anthropogenic Mars analogues (mine tailings) with laboratory-scale bioreactors that simulate those conditions and stimulate REE-biomobilisation. This investigation demonstrates that REE-mobilising microorganisms offer both a functional ISRU strategy and a valuable analogue for biosignature.

The biogeochemical characterisation of the Phalaborwa Igneous Complex (PIC, South Africa) tailing revealed the presence of REE-minerals and REE-bearing minerals, mainly monazite, fluorapatite, calcite and dolomite. The average concentration of REE was 1.5 g/kg (Gomez-Arias et al., 2022). Furthermore, indigenous bacteria, such as Sphingomonas sp., Novosphingobium sp. And Solirubrobacter sp., along with fungi, such as Alternaria sp., Aspergillus sp., and Sarocladium sp. were found to thrive in areas with elevated concentrations of REE (Cebekhulu et al., 2024).  Betweenness centrality highlighted the essential contribution of uncultured bacteria to the structure of the network in the tailings, where they act as bridges. Functionality analysis and bioleaching tests confirmed the ability of the indigenous microorganisms to leach REE through the production of organic acids and siderophores. REE mobilisation rates in microbial treatments exceeded abiotic controls by 2–5 fold, and bio-stimulated leaching experiments further enhanced REE release, suggesting that nutrient-enhanced bioleaching could be optimised for low-resource environments, including Mars.

Further experiments using Thermus scotoductus SA-01 (from deep gold mines in South Africa) and Clostridium sp. 2611 (from PIC) demonstrated additional REE-relevant phenotypes under extreme conditions. TEM-EDX analysis demonstrated that T. scotoductus precipitated europium intracellularly and extracellularly. FT-IR results confirmed that carbonyl and carboxyl groups were involved in the biosorption of Eu. Infrared and HR-XPS analysis demonstrated that Eu can be biomineralized by T. scotoductus SA-01 as Eu2(CO3)3 (Maleke et al., 2019a), while Clostridium sp. 2611 promoted bioprecipitation via reduction (Eu3+ to Eu2+) and cell surface binding (Maleke et al., 2019b). These traits suggest metabolic pathways and metal resistance mechanisms suitable for deployment in off-Earth biorecovery systems.

Together, this research outlines a biotechnology-based ISRU concept rooted in real microbial ecology and geochemistry. By bridging field studies, analogue experiments, and extreme microbial physiology, we propose REE biomining as a viable, low-energy alternative for resource extraction in planetary environments. In addition, the bioprecipitates of REE exhibit characteristic geochemical patterns, such as La/Ce ratios, molecular biomarkers, and microtextural mineral features. They could be detected by remote sensing or in situ analysis as REE biosignature proxies for astrobiological investigation of ancient or extant life.

This work was supported by the Spanish National Research Council (CSIC) through the MicroApp project (ref. COOPB23099). A Gómez-Arias acknowledges the “Juan de la Cierva” contract (JDC2022-049199-I) funded by MCIN/AEI/10.13039/501100011033 and the European Union “NextGenerationEU”/PRTR. The MICROLAVA project (PROYEXCEL_00185) and the contract DGP_POST_2024_01054, both funded by Junta de Andalucia/CUIII and FSE+ is also acknowledged.