Amils, R., Fernández Remolar, D. 2016. Acidophiles and Astrobiology. Acidophiles: Life in Extremely Acidic Environments 285-300
The NASA Astrobiology roadmap underlines the importance of extreme environments and the microorganisms that live in them to evaluate the possible existence of life outside of planet Earth. Acidophiles are of special astrobiological interest because the environments in which they thrive are generated by the metabolism of chemolithotrophic microorganisms that obtain energy from inorganic mineral substrates, a property that places them among the best candidates for a successful primitive energy conservation system. A thorough geomicrobiological characterization of an extreme acidic environment, the Rio Tinto basin, has revealed the importance of the iron cycle in the water column of the river and detected a higher level of metabolic diversity in the sediments and subsurface of the Iberian Pyrite Belt (IPB), due to the presence of micro-niches with environmental conditions different from the acidic waters with high redox potentials existing in the river. The identification of iron oxides and iron sulfates on the surface of Mars, similar to those produced in the Tinto basin by the metabolic activity of chemolithotrophic microorganisms, has given Rio Tinto the status of a geochemical and mineralogical terrestrial analogue of Mars. The argument that Mars’ environmental conditions are not suitable for methanogenesis could be challenged by the methane production observed in the sediments and the subsurface of the IPB.