The utilization of natural resources is an integral part of human activities, and the development of new methods for doing so is an important area of research. Microorganisms such as bacteria and archaea are capable of extracting metals from the environment in a process known as bioleaching. Bioleaching applications include extracting rare and valuable elements from ore by chemical techniques and decontaminating polluted environments. Accessible terrestrial supplies of rare earth elements (REEs) are becoming limited as a result of their high demand in advanced technology, which provides a motivation to investigate possible bioleaching in extraterrestrial environments.

In a study led by Charles Cockell and Rosa Santomartino of the University of Edinburgh, a series of experiments were conducted on the International Space Station (ISS) to study the effects of gravity on the capacity of different strains of bacteria to leach REEs from basaltic rock. In these experiments, three heterotrophic bacteria were cultivated in a biomining reactor under three different gravity conditions: simulated terrestrial (Earth) gravity, simulated Mars gravity, and microgravity. After the samples were returned to Earth, they were acidified and prepared for REE analysis using inductively coupled plasma mass spectrometry (ICP-MS). Although it has been previously demonstrated that microgravity can have significant effects on microbial metabolisms, the bioleaching capacity for two of the bacterial strains showed no statistical difference compared to a non-biological control (without microbes) on the ISS. However, the third strain, Sphingomonas desiccabilis, showed enhanced bioleaching capacity, as seen on Earth, compared to the non-biological control and retained this capacity under all gravity conditions. The results from these experiments show microbial specificity for bioleaching and are promising for future research and application of in situ resource utilization and space biomining on other bodies. READ MORE