Tinto Basin Research Articles

Validation of astrobiology technologies and instrument operations in terrestrial analogue environments

Terrestrial analogue environments are places on Earth that present geological or environmental conditions that are similar to those found on an extraterrestrial body. Analogue environments serve four functions: (1) learn about planetary processes on Earth and elsewhere; (2) test technologies, methodologies, and protocols; (3) train highly-qualified personnel, as well as science and operations teams; (4) engage the public, space agencies, media, and educators. Analogue studies also enable the development and validation of biosignatures and detection techniques. Analogue programs include the Canadian Space Agency's Canadian Analogue Research Network, NASA's Astrobiology Science and Technology for Exploring Planets, and NASA's Analog Missions. Examples of technology and instrument testing and validation in analogue environments include the Haughton-Mars Project Research Station, the Arctic Mars Analog Svalbard Expedition (AMASE), the Rio Tinto basin, and NASA's Field Integrated Design and Operations (FIDO).

Evaluation of Leptospirillum spp. in the Río Tinto, a model of interest to biohydrometallurgy

Members of the Leptospirillum genus have recently been found to be not only the most representative prokaryotes in the Río Tinto, a natural extreme acidic habitat, but also in other acidic environments (AMD), as well as in biohydrometallurgical operations. The main objective of this work was to better understand and control industrial biohydrometallurgical processes by studying the role of chemolithoautotrophic bacteria of this genus in the Tinto ecosystem. Different strains of Leptospirillum were isolated from the Tinto basin and physiologically and genetically characterized by Pulsed Field Gel Electrophoresis (PFGE) and DNA microarrays. Certain metabolic capabilities, such as iron oxidation, pyrite leaching and nitrogen fixation, were determined for each strain. Complementary molecular ecology techniques (fluorescence in situ hybridization (FISH and CARD-FISH) and 16S rRNA gene cloning) were used to study the microbial diversity and the distribution of leptospirilli along the iron gradient of the Tinto ecosystem.

Microbial Ecology of <i>Leptospirillum</i> spp. in Río Tinto, a Model of Interest to Biohydrometallurgy

Members of Leptospirillum genus have emerged not only as one of the most representative bacteria in the Río Tinto ecosystem, but also in other acidic environments (AMD), and in biohydrometallurgical operations. The main objective of this work was to study the role of chemolithoautotrophic bacteria of the genus Leptospirillum in the Río Tinto iron cycle (an extreme acidic environment, characterized by its constant low pH) to better understand and control industrial biohydrometallurgical processes. Different strains of Leptospirillum were isolated from the Río Tinto basin and physiologically and genetically characterized. Certain metabolic capabilities, such as pyrite leaching, iron oxidation and nitrogen fixation, were determined for each strain. Complementary molecular ecology techniques (FISH, CARD-FISH and cloning) were used to study the microbial diversity and the distribution of leptospirilli along the iron gradient in the different phases of Río Tinto: water column, anaerobic sediments and biofilms.

Importance of the iron cycle in biohydrometallurgy

After the discovery in the 1940s that acid mine drainage was mainly a consequence of the metabolism of chemolithoautotrophic microorganisms able to oxidize metal sulfides, mostly pyrite, much research has been performed to understand the ecology and the physiology of the microorganisms involved. At first, to prevent this environmental problem, and later to improve the efficiency of biohydrometallurgical processes. Until recently, bioenergetic considerations focused most of the attention on the sulfur oxidizing microorganisms. The demonstration that ferric iron was mainly responsible for the oxidation of pyrite has had profound implications not only on the comprehension of the phenomena but also on the microbial ecology of the correspondent systems. The Tinto River (Southwestern Spain) is an acidic environment with a high concentration of ferric iron generated by the metabolic activity of chemolithotrophic microorganisms growing in the rich complex sulfides of the Iberian Pyritic Belt (IPB). The use of conventional as well as molecular ecology tools identified the most representative members of the chemolithotrophic community of the Tinto Basin as prominent members of the iron cycle, highlighting the importance of this element in the oxidation of sulfides. Contrary to what was expected, the sulfur cycle seems to operate with rather low efficiency in the Tinto ecosystem. Interestingly enough, anaerobic geomicrobiology seems to play an important role in the system. All these observations strongly suggest that the iron cycle is extremely important for biohydrometallurgical processes in which sulfidic minerals are involved. An understanding of the properties of these versatile microorganisms and their ecology is essential to guarantee efficient and reliable biohydrometallurgical operations.

The Río Tinto Basin, Spain: Mineralogy, sedimentary geobiology, and implications for interpretation of outcrop rocks at Meridiani Planum, Mars

Exploration by the NASA rover Opportunity has revealed sulfate- and hematite-rich sedimentary rocks exposed in craters and other surface features of Meridiani Planum, Mars. Modern, Holocene, and Plio-Pleistocene deposits of the Rio Tinto, southwestern Spain, provide at least a partial environmental analog to Meridiani Planum rocks, facilitating our understanding of Meridiani mineral precipitation and diagenesis, while informing considerations of martian astrobiology. Oxidation, thought to be biologically mediated, of pyritic ore bodies by groundwaters in the source area of the Rio Tinto generates headwaters enriched in sulfuric acid and ferric iron. Seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite, while (Mg,Al,Fe(sup 3+))-copiapite, coquimbite, gypsum, and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action. During the wet season, hydrolysis of sulfate salts results in the precipitation of nanophase goethite. Holocene and Plio-Pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time. Hematite in Meridiani spherules also formed during diagenesis, although whether these replaced precursor goethite or precipitated directly from groundwaters is not known. The retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of Meridiani rocks. Diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry Rio Tinto environments. Organic matter does not persist in Rio Tinto sediments, but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers, surface blisters formed by biogenic gas, and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of Meridiani outcrops.