The Experts below are selected from a list of 27 Experts worldwide ranked by ideXlab platform
Giuseppe Etiope - One of the best experts on this subject based on the ideXlab platform.
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Low Temperature dunite hydration evaluating ch4 and h2 Production from h2o and co2
Geofluids, 2016Co-Authors: Anna Neubeck, D T Nguyen, Giuseppe EtiopeAbstract:Abiotic methane (CH4) and hydrogen (H2) produced after hydration of mafic/ultramafic rocks represent energy sources for microbes that may thrive in the deep subsurface regions of Earth and possibly on other planets. While H2 is a direct product of serpentinization, CH4 can form via Fischer–Tropsch Type (FTT) reactions (carbon reduction) that, due to potential H2 migration, can be spatially and temporally detached from serpentinization. We tested an alternative process hypothesized by some scholars, in which CO2 can be reduced through dunite hydration without initially added H2, implying that CH4 can form in the same serpentinized fluid–rock system. The experiment used natural dunite sand (Forsterite 92), CO2 with δ13C ~ −25‰ (VPDB), and a 1 mm dissolved SiO2 solution mixed in 30 glass bottles (118 mL) stored for up to 8 months at Low Temperature (50°C) to simulate land-based serpentinization systems. In addition, 30 control bottles without olivine were used as blanks. Trivial amounts of CH4 (orders of 0.2–0.9 ppmv) were detected in both samples and blanks, likely representing analytical noise; essentially, no significant amount of CH4 formed under the experimental conditions used in this work. Low amounts of H2 (~2.55 ± 1.39 ppmv) were generated, with Production yields that were one order of magnitude Lower than in previously published experiments. Moderate concentrations of SiO2 appeared to hinder Low-Temperature H2 Production. Our experiment confirms that the Low-Temperature reduction of CO2 into CH4 through direct olivine hydration, without initial H2, is sluggish and not straightforward, which is consistent with previous studies. The presence of substantial amounts of H2, as well as suitable metal catalysts, appears to be essential in the Low-Temperature Production of abiotic CH4, as observed in published FTT experiments.
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Low Temperature Production and exhalation of methane from serpentinized rocks on earth a potential analog for methane Production on mars
Icarus, 2013Co-Authors: Giuseppe Etiope, B L Ehlmann, Martin SchoellAbstract:We evaluate, based on terrestrial analogs, the potential flux, origin and isotopic signature of methane (CH_4) from serpentinized or serpentinizing rocks on Mars. The Tekirova ophiolites, in Turkey, have been shown to release, either via focused vents or through diffuse microseepage, substantial amounts of CH_4 which could be produced via catalyzed abiotic methanation (Sabatier reaction) at Low Temperatures (<50 °C). Serpentinized ultramafic rocks on Mars are likely to have necessary chemical constituents for methane Production and fractures for release of gas to the atmosphere, similar to those on Earth. A simple, first-order estimation gas-advection model suggests that methane fluxes on the order of several mg m^(−2) d^(−1), similar to microseepage observed in terrestrial ophiolites, could occur in martian rocks. High Temperature, hydrothermal conditions may not be necessary for abiotic CH_4 synthesis on Mars: Low Temperature (<50 °C) methanation is possible in the presence of catalysts like ruthenium, rhodium or, more commonly, chromium minerals, which occur in terrestrial ophiolites as in martian mantle meteorites. The terrestrial analog environment of abiotic microseepage may thus explain Production of methane on Mars in the ancient past or at present. The wide range of martian ^(12)C/^(13)C and D/H ratios and the potential secondary alteration of CH_4 by abiotic oxidation, as observed on Earth, could result in large isotope variations of methane on Mars. CH_4 isotopic composition alone may not alLow definitive determination of biotic vs. abiotic gas origin. Using our terrestrial vs. martian analysis as guide to future Mars exploration we propose that direct methane and ethane gas detection and isotopic measurements on the ground over serpentinized/serpentinizing rocks should be considered in developing future strategies for unraveling the source and origin of methane on Mars.
Martin Schoell - One of the best experts on this subject based on the ideXlab platform.
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Low Temperature Production and exhalation of methane from serpentinized rocks on earth a potential analog for methane Production on mars
Icarus, 2013Co-Authors: Giuseppe Etiope, B L Ehlmann, Martin SchoellAbstract:We evaluate, based on terrestrial analogs, the potential flux, origin and isotopic signature of methane (CH_4) from serpentinized or serpentinizing rocks on Mars. The Tekirova ophiolites, in Turkey, have been shown to release, either via focused vents or through diffuse microseepage, substantial amounts of CH_4 which could be produced via catalyzed abiotic methanation (Sabatier reaction) at Low Temperatures (<50 °C). Serpentinized ultramafic rocks on Mars are likely to have necessary chemical constituents for methane Production and fractures for release of gas to the atmosphere, similar to those on Earth. A simple, first-order estimation gas-advection model suggests that methane fluxes on the order of several mg m^(−2) d^(−1), similar to microseepage observed in terrestrial ophiolites, could occur in martian rocks. High Temperature, hydrothermal conditions may not be necessary for abiotic CH_4 synthesis on Mars: Low Temperature (<50 °C) methanation is possible in the presence of catalysts like ruthenium, rhodium or, more commonly, chromium minerals, which occur in terrestrial ophiolites as in martian mantle meteorites. The terrestrial analog environment of abiotic microseepage may thus explain Production of methane on Mars in the ancient past or at present. The wide range of martian ^(12)C/^(13)C and D/H ratios and the potential secondary alteration of CH_4 by abiotic oxidation, as observed on Earth, could result in large isotope variations of methane on Mars. CH_4 isotopic composition alone may not alLow definitive determination of biotic vs. abiotic gas origin. Using our terrestrial vs. martian analysis as guide to future Mars exploration we propose that direct methane and ethane gas detection and isotopic measurements on the ground over serpentinized/serpentinizing rocks should be considered in developing future strategies for unraveling the source and origin of methane on Mars.
J M F Ferreira - One of the best experts on this subject based on the ideXlab platform.
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Low Temperature Production of glass ceramics in the anorthite diopside system via sintering and crystallization of glass powder compacts
Ceramics International, 2008Co-Authors: V M F Marques, Dilshat U Tulyaganov, Simeon Agathopoulos, J M F FerreiraAbstract:Abstract The Production of glass ceramics (GCs) with theoretical anorthite–diopside (An–Di) weight ratios of 60/40, 50/50 and 45/55 via sintering and crystallization of glass powder compacts was investigated at different Temperatures between 800 and 950 °C. The investigated compositions are located in the cross-section of the ternary fluorapatite–An–Di system close to An–Di binary joint, with constant fluorapatite content of 4.8 wt.%. Two different groups of glass powders, with mean particle size of 2 and 10 μm, were used. The experimental results showed that sintering is almost complete at 800 °C, preceding crystallization, which takes place via surface crystallization mechanism. The properties values of the produced GCs, which are the best for the composition close to An–Di eutectic line, are discussed with respect to the evolution of crystalline phases and the microstructure over increasing firing Temperature. Under the technology perspective, the investigated processing route is significantly superior in comparison to the attempts reported in earlier studies.
V M F Marques - One of the best experts on this subject based on the ideXlab platform.
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Low Temperature Production of glass ceramics in the anorthite diopside system via sintering and crystallization of glass powder compacts
Ceramics International, 2008Co-Authors: V M F Marques, Dilshat U Tulyaganov, Simeon Agathopoulos, J M F FerreiraAbstract:Abstract The Production of glass ceramics (GCs) with theoretical anorthite–diopside (An–Di) weight ratios of 60/40, 50/50 and 45/55 via sintering and crystallization of glass powder compacts was investigated at different Temperatures between 800 and 950 °C. The investigated compositions are located in the cross-section of the ternary fluorapatite–An–Di system close to An–Di binary joint, with constant fluorapatite content of 4.8 wt.%. Two different groups of glass powders, with mean particle size of 2 and 10 μm, were used. The experimental results showed that sintering is almost complete at 800 °C, preceding crystallization, which takes place via surface crystallization mechanism. The properties values of the produced GCs, which are the best for the composition close to An–Di eutectic line, are discussed with respect to the evolution of crystalline phases and the microstructure over increasing firing Temperature. Under the technology perspective, the investigated processing route is significantly superior in comparison to the attempts reported in earlier studies.
Anna Neubeck - One of the best experts on this subject based on the ideXlab platform.
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Low Temperature dunite hydration evaluating ch4 and h2 Production from h2o and co2
Geofluids, 2016Co-Authors: Anna Neubeck, D T Nguyen, Giuseppe EtiopeAbstract:Abiotic methane (CH4) and hydrogen (H2) produced after hydration of mafic/ultramafic rocks represent energy sources for microbes that may thrive in the deep subsurface regions of Earth and possibly on other planets. While H2 is a direct product of serpentinization, CH4 can form via Fischer–Tropsch Type (FTT) reactions (carbon reduction) that, due to potential H2 migration, can be spatially and temporally detached from serpentinization. We tested an alternative process hypothesized by some scholars, in which CO2 can be reduced through dunite hydration without initially added H2, implying that CH4 can form in the same serpentinized fluid–rock system. The experiment used natural dunite sand (Forsterite 92), CO2 with δ13C ~ −25‰ (VPDB), and a 1 mm dissolved SiO2 solution mixed in 30 glass bottles (118 mL) stored for up to 8 months at Low Temperature (50°C) to simulate land-based serpentinization systems. In addition, 30 control bottles without olivine were used as blanks. Trivial amounts of CH4 (orders of 0.2–0.9 ppmv) were detected in both samples and blanks, likely representing analytical noise; essentially, no significant amount of CH4 formed under the experimental conditions used in this work. Low amounts of H2 (~2.55 ± 1.39 ppmv) were generated, with Production yields that were one order of magnitude Lower than in previously published experiments. Moderate concentrations of SiO2 appeared to hinder Low-Temperature H2 Production. Our experiment confirms that the Low-Temperature reduction of CO2 into CH4 through direct olivine hydration, without initial H2, is sluggish and not straightforward, which is consistent with previous studies. The presence of substantial amounts of H2, as well as suitable metal catalysts, appears to be essential in the Low-Temperature Production of abiotic CH4, as observed in published FTT experiments.
