Río Tinto: A Geochemical and Mineralogical Terrestrial Analogue of Mars

Abstract

The geomicrobiological characterization of the water column and sediments of Río Tinto (Huelva, Southwestern Spain) have proven the importance of the iron and the sulfur cycles, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals), but also in maintaining the high level of microbial diversity detected in the basin. It has been proven that the extreme acidic conditions of Río Tinto basin are not the product of 5000 years of mining activity in the area, but the consequence of an active underground bioreactor that obtains its energy from the massive sulfidic minerals existing in the Iberian Pyrite Belt. Two drilling projects, MARTE (Mars Astrobiology Research and Technology Experiment) (2003–2006) and IPBSL (Iberian Pyrite Belt Subsurface Life Detection) (2011–2015), were developed and carried out to provide evidence of subsurface microbial activity and the potential resources that support these activities. The reduced substrates and the oxidants that drive the system appear to come from the rock matrix. These resources need only groundwater to launch diverse microbial metabolisms. The similarities between the vast sulfate and iron oxide deposits on Mars and the main sulfide bioleaching products found in the Tinto basin have given Río Tinto the status of a geochemical and mineralogical Mars terrestrial analogue.

Pristine but metal-rich Río Sucio (Dirty River) is dominated by Gallionella and other iron-sulfur oxidizing microbes

“…One of the most extensively studied ARD environments is the Río Tinto system that originates in the Iberian Pyritic Belt (IPB) of Spain (González-Toril et al 2003;López-Archilla et al 2004;García-Moyano et al 2012;Sánchez-Andrea et al 2012). Because the IPB has been extensively mined for more than 4500 years, there is controversy about the causes of the extreme acidity and heavy metal pollution of the river, with some authorities claiming that they are due to human activity (Olías and Nieto 2015) and others arguing that they basically result from natural activities within the IPB (Fernández-Remolar 2003; Amils et al 2014). Due to the extensive anthropogenic impacts in most ARD systems that have been studied, with the consequent changes in geology and hydrology, it is difficult to separate natural from engineered causes of pollution.…”

Fungal Iron Biomineralization in Río Tinto

“…Of the Ascomycetes, 52% clustered within the Eurotiomycetes class, while 27% grouped with the Dothideomycetes, 17% with the Sordariomycetes, and the rest of the isolates with the Helotiales (2%). Metal tolerance tests performed on these isolates showed, in general, a high level of tolerance to toxic heavy metals, much higher than the concentrations detected in the river [9].…”

“…Of the Ascomycetes, 52% clustered within the Eurotiomycetes class, while 27% grouped with the Dothideomycetes, 17% with the Sordariomycetes, and the rest of the isolates with the Helotiales (2%). Metal tolerance tests performed on these isolates showed, in general, a high level of tolerance to toxic heavy metals, much higher than the concentrations detected in the river [9]. In extreme acidic environments with a high content of toxic metals such as Río Tinto, fungal development is possible due to several strategies, such as mineral precipitation (e.g., [10,11]).…”

Geochemistry and Mineralogy of Western Australian Salt Lake Sediments: Implications for Meridiani Planum on Mars

“…The highly acidic Rio Tinto in Spain, another terrestrial analogue for Meridiani Planum, sustains a 410 microbially driven Fe-redox cycle (Amils et al, 2014 …”