Ricardo Amils - Academia.edu (original) (raw)
Papers by Ricardo Amils
Cellular Origin, Life in Extreme Habitats and Astrobiology
Environmental Microbiology
Microbial activity is a major contributor to the biogeochemical cycles that make up the life supp... more Microbial activity is a major contributor to the biogeochemical cycles that make up the life support system of planet Earth. A 613 m deep geomicrobiological perforation and a systematic multi‐analytical characterization revealed an unexpected diversity associated with the rock matrix microbiome that operates in the subsurface of the Iberian Pyrite Belt (IPB). Members of 1 class and 16 genera were deemed the most representative microorganisms of the IPB deep subsurface and selected for a deeper analysis. The use of fluorescence in situ hybridization allowed not only the identification of microorganisms but also the detection of novel activities in the subsurface such as anaerobic ammonium oxidation (ANAMMOX) and anaerobic methane oxidation, the co‐occurrence of microorganisms able to maintain complementary metabolic activities and the existence of biofilms. The use of enrichment cultures sensed the presence of five different complementary metabolic activities along the length of the ...
Meteoritics & Planetary Science, 2011
– A model is presented in which the aqueous conditions needed to generate phyllosilicate minerals... more – A model is presented in which the aqueous conditions needed to generate phyllosilicate minerals in the absence of carbonates found in the ancient Noachian crust are maintained by an early CO2‐rich atmosphere, that, together with iron (II) oxidation, would prevent carbonate formation at the surface. After cessation of the internal magnetic dynamo, a CO2‐rich primordial atmosphere was stripped by interactions with the solar wind and surface conditions evolved from humid to arid, with ground waters partially dissolving subsurface carbonate and sulfide minerals to produce acid‐sulfate evaporitic deposits in areas with upwelling ground water. In a subsequent geochemical state (Late Noachian to Hesperian), surface and subsurface acidic solutions were neutralized in the subsurface through interaction with basaltic crust, allowing the precipitation of secondary carbonates. This model suggests that, in the early Noachian, the surface waters of Mars maintained acidity because of a drop in temperature. This would have favored increased dissolution of CO2 and a reduction in atmospheric pressure. In this scenario, physicochemical conditions precluded the formation of surface carbonates, but induced the precipitation of carbonates in the subsurface.
Reconstruction of the probable habitats hosting the detected microbial communities through the in... more Reconstruction of the probable habitats hosting the detected microbial communities through the integration of the geobiological data obtained from the MARTE drilling campaigns, TEM sounding and field surface geological survey
Journal of Geophysical Research, 2003
Introduction: Among the conceivable modern habitats to be explored for searching life on Mars are... more Introduction: Among the conceivable modern habitats to be explored for searching life on Mars are those potentially developed underground. Subsurface habitats are currently environments that, under certain physicochemical circumstances, have high thermal and hydrochemical stability [1, 2]. In planets like Mars lacking an atmospheric shield, such systems are obviously protected against radiation, which strongly alters the structure of biological macromolecules. Low porosity but fractured aquifers currently emplaced inside ancient volcanosedimentary and hydrothermal systems act as excellent habitats [3] due to its thermal and geochemical properties. In these aquifers the temperature is controlled by a thermal balance between conduction and advection processes, which are driven by the rock composition, geological structure, water turnover of aquifers and heat generation from geothermal processes or chemical reactions [4]. Moreover, microbial communities based on chemolithotrophy can obtain energy by the oxidation of metallic ores that are currently associated to these environments. Such a community core may sustain a trophic web composed of non-autotrophic forms like heterotrophic bacteria, fungi and protozoa. The MARTE project [5] combines both the acquisition of scientific knowledge on Terrestrial cryptic communities to be found in ancient hydrothermal/volcanosedimentary systems, which may be common on Mars, and the technology development for detecting them in the Martian underground. Such a complex task demands robotic and instrument systems for exploring, sampling, and analyzing subsurface samples. This paper shows the first geobiological data recovered during the "ground truth" drilling operations from the MARTE experiment (see ref. 6) that were performed recently in the ancient hydrothermal system of the Río Tinto Basin. MARTE project objectives are summarized in [5, 6]. The ground truth drilling, the first activity of the MARTE project, started in September '03 and is taking place in Peña de Hierro, near the source waters of the Tinto River. The river is sourced in the Iberian Pyrite Belt [7, 8], one of the largest deposits of sulfide minerals in the world. Geological and hydrochemical settings: The Tinto River Basin has its source close to Nerva and Ríotinto villages see [6] in the southern margin of the Sierra de Aracena that is located in the Iberian Pyritic Belt. This extensive geological unit is made up by
Proceedings of the National Academy of Sciences of the United States of America, Oct 16, 2018
Cyanobacteria are ecologically versatile microorganisms inhabiting most environments, ranging fro... more Cyanobacteria are ecologically versatile microorganisms inhabiting most environments, ranging from marine systems to arid deserts. Although they possess several pathways for light-independent energy generation, until now their ecological range appeared to be restricted to environments with at least occasional exposure to sunlight. Here we present molecular, microscopic, and metagenomic evidence that cyanobacteria predominate in deep subsurface rock samples from the Iberian Pyrite Belt Mars analog (southwestern Spain). Metagenomics showed the potential for a hydrogen-based lithoautotrophic cyanobacterial metabolism. Collectively, our results suggest that they may play an important role as primary producers within the deep-Earth biosphere. Our description of this previously unknown ecological niche for cyanobacteria paves the way for models on their origin and evolution, as well as on their potential presence in current or primitive biospheres in other planetary bodies, and on the ext...
The geomicrobial characterization of the Tinto River (Iberian Pyritic Belt, Southwestern Spain) h... more The geomicrobial characterization of the Tinto River (Iberian Pyritic Belt, Southwestern Spain) has recently proven the importance of the iron cycle, not only in the generation of the extreme conditions of the habitat (low pH and high concentration of heavy metals), but also in the maintenance of a high level of microbial diversity. The presence of vast deposits of iron oxides on Mars and the physico-chemical properties of this element as a source of energy, as protection from radiation and oxidation as well as to control the pH the habitat, make the possible existence of an active geomicrobial iron system on the red planet worthy of study. In this paper these aspects are outlined and the current investigation using the Tinto River as a terrestrial analogue discussed.
Minerals, 2016
Although there are many studies on biomineralization processes, most of them focus on the role of... more Although there are many studies on biomineralization processes, most of them focus on the role of prokaryotes. As fungi play an important role in different geological and biogeochemical processes, it was considered of interest to evaluate their role in a natural extreme acidic environment, Río Tinto, which has a high level of fungal diversity and a high concentration of metals. In this work we report, for the first time, the generation of iron oxyhydroxide minerals by the fungal community in a specific location of the Tinto basin. Using Transmission Electron Microscopy (TEM) and High Angle Angular Dark Field coupled with Scanning Transmission Electron Microscopy (HAADF-STEM) and Energy-Dispersive X-ray Spectroscopy (EDX), we observed fungal structures involved in the formation of iron oxyhydroxide minerals in mineralized sediment samples from the Río Tinto basin. Although Río Tinto waters are supersaturated in these minerals, they do not precipitate due to their slow precipitation kinetics. The presence of fungi, which simply provide charged surfaces for metal binding, favors the precipitation of Fe oxyhydroxides by overcoming these kinetic barriers. These results prove that the fungal community of Río Tinto participates very actively in the geochemical processes that take place there.
Etica Y Biotecnologia 1993 Isbn 84 87840 37 X Pags 31 74, 1993
Astrobiology, 2005
Chemolithoautotrophy based on reduced inorganic minerals is considered a primitive energy transdu... more Chemolithoautotrophy based on reduced inorganic minerals is considered a primitive energy transduction system. Evidence that a high number of meteorites crashed into the planet during the early period of Earth history led us to test the ability of iron-oxidizing bacteria to grow using iron meteorites as their source of energy. Here we report the growth of two acidophilic iron-oxidizing bacteria, Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans, on a piece of the Toluca meteorite as the only source of energy. The alteration of the surface of the exposed piece of meteorite, the solubilization of its oxidized metal constituents, mainly ferric iron, and the formation of goethite precipitates all clearly indicate that iron-meteoritebased chemolithotrophic metabolism is viable.
Astrobiology, 2003
Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa&amp... more Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for microbial detection and characterization in hypersaline environments makes this methodology strongly advisable for future Europa astrobiological missions.
Environmental microbiology, Sep 28, 2017
Salar de Uyuni (SdU), with a geological history that reflects 50,000 years of climate change, is ... more Salar de Uyuni (SdU), with a geological history that reflects 50,000 years of climate change, is the largest hypersaline salt flat on Earth and is estimated to be the biggest lithium reservoir in the world. Its salinity reaches saturation levels for NaCl, a kosmotropic salt, and high concentrations of MgCL2 and LiCl, both salts considered important chaotrophic stressors. In addition, extreme temperatures, anoxic conditions, high UV irradiance, high albedo, and extremely low concentrations of phosphorous, make SdU a unique natural extreme environment in which to contrast hypotheses about limiting factors of life diversification. Geophysical studies of brines from different sampling stations show that water activity is rather constant along SdU. Geochemical measurements show significant differences in magnesium concentration, ranging from 0.2 to 2M. This work analyses the prokaryotic diversity and community structure at four SdU sampling stations, selected according to their location ...
Geology, 2006
The presence of methane has been recently detected in the martian atmosphere, suggesting a contem... more The presence of methane has been recently detected in the martian atmosphere, suggesting a contemporary source such as volcanism or microbial activity. Here we show that methane may be released by the destabilization of methane clathrate hydrates, triggered by the interglacial climate change starting 0.4 Ma. Clathrate hydrates are nonstoichiometric crystalline compounds in which a water ice lattice forms cages that contain apolar gas molecules, such as methane [CH 4 •nH 2 O] and carbon dioxide [CO 2 •nH 2 O]. The loss of shallow ground ice eliminates confining pressure, initiating the destabilization of clathrate hydrates and the release of methane to the atmosphere. This alternative process does not restrict the methane's age to 430 yr (maximum residence time of methane gas in martian atmosphere), because clathrate hydrates can preserve (encage) methane of ancient origin for long time periods.
Earth and Planetary Science Letters, 2014
In our reply to the comment on "Identification of the subsurface sulfide bodies responsible for a... more In our reply to the comment on "Identification of the subsurface sulfide bodies responsible for acidity in Río Tinto source water, Spain" we provide additional data supporting the Río Tinto acidic environment as a natural system fed by the biooxidation of underground sulfides. The age of surface solutions has been refined by correcting the tritium data in relation to the geographical emplacement of the acidic system. In addition to this, we have included tritium data for subsurface solutions and we have used modeling software that provides groundwater mean residence time by means of gaseous tracers. As a main result, the tritium data support the fact that Río Tinto waters are fed in a subsurface ancient source from the microbial oxidation of the sulfides. Furthermore, we also include chronostratigraphic and geochronological data that support a discontinuous record over time of a lasting extreme environment dating back to the Late Paleocene times. DOI of original article: http://dx.
Earth and Planetary Science Letters, 2014
We present initial results from the first metagenomic sequencing effort in the Rio Tinto, with sp... more We present initial results from the first metagenomic sequencing effort in the Rio Tinto, with special attention paid to detections of sulfate-reducing bacteria and magnetotactic bacteria.
Third European Workshop on Exo Astrobiology, Mar 1, 2004
An important subject of astrobiological interest is the study of the effect of ultraviolet radiat... more An important subject of astrobiological interest is the study of the effect of ultraviolet radiation on microorganisms and their protection mechanisms against this damaging agent. UV radiation is considered highly mutagenic and sterilizing, especially during the period of origin of life on Earth when the absence of the ozone layer meant there was no effective protection against ultraviolet radiation from the sun. Ferric iron, the product of iron metabolism, as a consequence of its spectral properties, has been suggested to provide protection against radiation making the study of its protective effect on acidophilic microorganisms from the Tinto ecosystem of interest in order to gain information about its possible implications in the development of life during the Archaean as well on planets lacking a protective atmosphere such as Mars. The studies described in this paper constitute preliminary experiments.
36Th Annual Lunar and Planetary Science Conference, Mar 1, 2005
Hemispheric acidic oceans on Mars represent a localized stage in the Noachian. Shallow surface ac... more Hemispheric acidic oceans on Mars represent a localized stage in the Noachian. Shallow surface acidic water have also been flowing recurrently on several martian locations during the Hesperian and the Amazonian. Life may have gained a foothold in these environments.
Cellular Origin, Life in Extreme Habitats and Astrobiology
Environmental Microbiology
Microbial activity is a major contributor to the biogeochemical cycles that make up the life supp... more Microbial activity is a major contributor to the biogeochemical cycles that make up the life support system of planet Earth. A 613 m deep geomicrobiological perforation and a systematic multi‐analytical characterization revealed an unexpected diversity associated with the rock matrix microbiome that operates in the subsurface of the Iberian Pyrite Belt (IPB). Members of 1 class and 16 genera were deemed the most representative microorganisms of the IPB deep subsurface and selected for a deeper analysis. The use of fluorescence in situ hybridization allowed not only the identification of microorganisms but also the detection of novel activities in the subsurface such as anaerobic ammonium oxidation (ANAMMOX) and anaerobic methane oxidation, the co‐occurrence of microorganisms able to maintain complementary metabolic activities and the existence of biofilms. The use of enrichment cultures sensed the presence of five different complementary metabolic activities along the length of the ...
Meteoritics & Planetary Science, 2011
– A model is presented in which the aqueous conditions needed to generate phyllosilicate minerals... more – A model is presented in which the aqueous conditions needed to generate phyllosilicate minerals in the absence of carbonates found in the ancient Noachian crust are maintained by an early CO2‐rich atmosphere, that, together with iron (II) oxidation, would prevent carbonate formation at the surface. After cessation of the internal magnetic dynamo, a CO2‐rich primordial atmosphere was stripped by interactions with the solar wind and surface conditions evolved from humid to arid, with ground waters partially dissolving subsurface carbonate and sulfide minerals to produce acid‐sulfate evaporitic deposits in areas with upwelling ground water. In a subsequent geochemical state (Late Noachian to Hesperian), surface and subsurface acidic solutions were neutralized in the subsurface through interaction with basaltic crust, allowing the precipitation of secondary carbonates. This model suggests that, in the early Noachian, the surface waters of Mars maintained acidity because of a drop in temperature. This would have favored increased dissolution of CO2 and a reduction in atmospheric pressure. In this scenario, physicochemical conditions precluded the formation of surface carbonates, but induced the precipitation of carbonates in the subsurface.
Reconstruction of the probable habitats hosting the detected microbial communities through the in... more Reconstruction of the probable habitats hosting the detected microbial communities through the integration of the geobiological data obtained from the MARTE drilling campaigns, TEM sounding and field surface geological survey
Journal of Geophysical Research, 2003
Introduction: Among the conceivable modern habitats to be explored for searching life on Mars are... more Introduction: Among the conceivable modern habitats to be explored for searching life on Mars are those potentially developed underground. Subsurface habitats are currently environments that, under certain physicochemical circumstances, have high thermal and hydrochemical stability [1, 2]. In planets like Mars lacking an atmospheric shield, such systems are obviously protected against radiation, which strongly alters the structure of biological macromolecules. Low porosity but fractured aquifers currently emplaced inside ancient volcanosedimentary and hydrothermal systems act as excellent habitats [3] due to its thermal and geochemical properties. In these aquifers the temperature is controlled by a thermal balance between conduction and advection processes, which are driven by the rock composition, geological structure, water turnover of aquifers and heat generation from geothermal processes or chemical reactions [4]. Moreover, microbial communities based on chemolithotrophy can obtain energy by the oxidation of metallic ores that are currently associated to these environments. Such a community core may sustain a trophic web composed of non-autotrophic forms like heterotrophic bacteria, fungi and protozoa. The MARTE project [5] combines both the acquisition of scientific knowledge on Terrestrial cryptic communities to be found in ancient hydrothermal/volcanosedimentary systems, which may be common on Mars, and the technology development for detecting them in the Martian underground. Such a complex task demands robotic and instrument systems for exploring, sampling, and analyzing subsurface samples. This paper shows the first geobiological data recovered during the "ground truth" drilling operations from the MARTE experiment (see ref. 6) that were performed recently in the ancient hydrothermal system of the Río Tinto Basin. MARTE project objectives are summarized in [5, 6]. The ground truth drilling, the first activity of the MARTE project, started in September '03 and is taking place in Peña de Hierro, near the source waters of the Tinto River. The river is sourced in the Iberian Pyrite Belt [7, 8], one of the largest deposits of sulfide minerals in the world. Geological and hydrochemical settings: The Tinto River Basin has its source close to Nerva and Ríotinto villages see [6] in the southern margin of the Sierra de Aracena that is located in the Iberian Pyritic Belt. This extensive geological unit is made up by
Proceedings of the National Academy of Sciences of the United States of America, Oct 16, 2018
Cyanobacteria are ecologically versatile microorganisms inhabiting most environments, ranging fro... more Cyanobacteria are ecologically versatile microorganisms inhabiting most environments, ranging from marine systems to arid deserts. Although they possess several pathways for light-independent energy generation, until now their ecological range appeared to be restricted to environments with at least occasional exposure to sunlight. Here we present molecular, microscopic, and metagenomic evidence that cyanobacteria predominate in deep subsurface rock samples from the Iberian Pyrite Belt Mars analog (southwestern Spain). Metagenomics showed the potential for a hydrogen-based lithoautotrophic cyanobacterial metabolism. Collectively, our results suggest that they may play an important role as primary producers within the deep-Earth biosphere. Our description of this previously unknown ecological niche for cyanobacteria paves the way for models on their origin and evolution, as well as on their potential presence in current or primitive biospheres in other planetary bodies, and on the ext...
The geomicrobial characterization of the Tinto River (Iberian Pyritic Belt, Southwestern Spain) h... more The geomicrobial characterization of the Tinto River (Iberian Pyritic Belt, Southwestern Spain) has recently proven the importance of the iron cycle, not only in the generation of the extreme conditions of the habitat (low pH and high concentration of heavy metals), but also in the maintenance of a high level of microbial diversity. The presence of vast deposits of iron oxides on Mars and the physico-chemical properties of this element as a source of energy, as protection from radiation and oxidation as well as to control the pH the habitat, make the possible existence of an active geomicrobial iron system on the red planet worthy of study. In this paper these aspects are outlined and the current investigation using the Tinto River as a terrestrial analogue discussed.
Minerals, 2016
Although there are many studies on biomineralization processes, most of them focus on the role of... more Although there are many studies on biomineralization processes, most of them focus on the role of prokaryotes. As fungi play an important role in different geological and biogeochemical processes, it was considered of interest to evaluate their role in a natural extreme acidic environment, Río Tinto, which has a high level of fungal diversity and a high concentration of metals. In this work we report, for the first time, the generation of iron oxyhydroxide minerals by the fungal community in a specific location of the Tinto basin. Using Transmission Electron Microscopy (TEM) and High Angle Angular Dark Field coupled with Scanning Transmission Electron Microscopy (HAADF-STEM) and Energy-Dispersive X-ray Spectroscopy (EDX), we observed fungal structures involved in the formation of iron oxyhydroxide minerals in mineralized sediment samples from the Río Tinto basin. Although Río Tinto waters are supersaturated in these minerals, they do not precipitate due to their slow precipitation kinetics. The presence of fungi, which simply provide charged surfaces for metal binding, favors the precipitation of Fe oxyhydroxides by overcoming these kinetic barriers. These results prove that the fungal community of Río Tinto participates very actively in the geochemical processes that take place there.
Etica Y Biotecnologia 1993 Isbn 84 87840 37 X Pags 31 74, 1993
Astrobiology, 2005
Chemolithoautotrophy based on reduced inorganic minerals is considered a primitive energy transdu... more Chemolithoautotrophy based on reduced inorganic minerals is considered a primitive energy transduction system. Evidence that a high number of meteorites crashed into the planet during the early period of Earth history led us to test the ability of iron-oxidizing bacteria to grow using iron meteorites as their source of energy. Here we report the growth of two acidophilic iron-oxidizing bacteria, Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans, on a piece of the Toluca meteorite as the only source of energy. The alteration of the surface of the exposed piece of meteorite, the solubilization of its oxidized metal constituents, mainly ferric iron, and the formation of goethite precipitates all clearly indicate that iron-meteoritebased chemolithotrophic metabolism is viable.
Astrobiology, 2003
Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa&amp... more Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for microbial detection and characterization in hypersaline environments makes this methodology strongly advisable for future Europa astrobiological missions.
Environmental microbiology, Sep 28, 2017
Salar de Uyuni (SdU), with a geological history that reflects 50,000 years of climate change, is ... more Salar de Uyuni (SdU), with a geological history that reflects 50,000 years of climate change, is the largest hypersaline salt flat on Earth and is estimated to be the biggest lithium reservoir in the world. Its salinity reaches saturation levels for NaCl, a kosmotropic salt, and high concentrations of MgCL2 and LiCl, both salts considered important chaotrophic stressors. In addition, extreme temperatures, anoxic conditions, high UV irradiance, high albedo, and extremely low concentrations of phosphorous, make SdU a unique natural extreme environment in which to contrast hypotheses about limiting factors of life diversification. Geophysical studies of brines from different sampling stations show that water activity is rather constant along SdU. Geochemical measurements show significant differences in magnesium concentration, ranging from 0.2 to 2M. This work analyses the prokaryotic diversity and community structure at four SdU sampling stations, selected according to their location ...
Geology, 2006
The presence of methane has been recently detected in the martian atmosphere, suggesting a contem... more The presence of methane has been recently detected in the martian atmosphere, suggesting a contemporary source such as volcanism or microbial activity. Here we show that methane may be released by the destabilization of methane clathrate hydrates, triggered by the interglacial climate change starting 0.4 Ma. Clathrate hydrates are nonstoichiometric crystalline compounds in which a water ice lattice forms cages that contain apolar gas molecules, such as methane [CH 4 •nH 2 O] and carbon dioxide [CO 2 •nH 2 O]. The loss of shallow ground ice eliminates confining pressure, initiating the destabilization of clathrate hydrates and the release of methane to the atmosphere. This alternative process does not restrict the methane's age to 430 yr (maximum residence time of methane gas in martian atmosphere), because clathrate hydrates can preserve (encage) methane of ancient origin for long time periods.
Earth and Planetary Science Letters, 2014
In our reply to the comment on "Identification of the subsurface sulfide bodies responsible for a... more In our reply to the comment on "Identification of the subsurface sulfide bodies responsible for acidity in Río Tinto source water, Spain" we provide additional data supporting the Río Tinto acidic environment as a natural system fed by the biooxidation of underground sulfides. The age of surface solutions has been refined by correcting the tritium data in relation to the geographical emplacement of the acidic system. In addition to this, we have included tritium data for subsurface solutions and we have used modeling software that provides groundwater mean residence time by means of gaseous tracers. As a main result, the tritium data support the fact that Río Tinto waters are fed in a subsurface ancient source from the microbial oxidation of the sulfides. Furthermore, we also include chronostratigraphic and geochronological data that support a discontinuous record over time of a lasting extreme environment dating back to the Late Paleocene times. DOI of original article: http://dx.
Earth and Planetary Science Letters, 2014
We present initial results from the first metagenomic sequencing effort in the Rio Tinto, with sp... more We present initial results from the first metagenomic sequencing effort in the Rio Tinto, with special attention paid to detections of sulfate-reducing bacteria and magnetotactic bacteria.
Third European Workshop on Exo Astrobiology, Mar 1, 2004
An important subject of astrobiological interest is the study of the effect of ultraviolet radiat... more An important subject of astrobiological interest is the study of the effect of ultraviolet radiation on microorganisms and their protection mechanisms against this damaging agent. UV radiation is considered highly mutagenic and sterilizing, especially during the period of origin of life on Earth when the absence of the ozone layer meant there was no effective protection against ultraviolet radiation from the sun. Ferric iron, the product of iron metabolism, as a consequence of its spectral properties, has been suggested to provide protection against radiation making the study of its protective effect on acidophilic microorganisms from the Tinto ecosystem of interest in order to gain information about its possible implications in the development of life during the Archaean as well on planets lacking a protective atmosphere such as Mars. The studies described in this paper constitute preliminary experiments.
36Th Annual Lunar and Planetary Science Conference, Mar 1, 2005
Hemispheric acidic oceans on Mars represent a localized stage in the Noachian. Shallow surface ac... more Hemispheric acidic oceans on Mars represent a localized stage in the Noachian. Shallow surface acidic water have also been flowing recurrently on several martian locations during the Hesperian and the Amazonian. Life may have gained a foothold in these environments.