| 1. |
- de Souza, Claudio M. D., et al.
(författare)
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Interaction of forsterite-91 with distilled water and artificial seawater : a prebiotic chemistry experiment
- 2013
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Ingår i: International Journal of Astrobiology. - 1473-5504 .- 1475-3006. ; 12:2, s. 135-143
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the interactions between forsterite-91 with distilled water and forsterite-91 with artificial seawater were studied at two pHs (2.0 and 8.0) using different techniques. A large increase in pH was observed for samples incubated at an initially acidic pH (2.0) due to the dissolution of forsterite-91 in distilled water and artificial seawater. Thus, in acidic hydrothermal vents, an increase in the amount of hydrocarbons and magnetite should be expected due to the release of Fe(II). The pH(PZC) decreased and the pH(IEP) increased when forsterite-91 was treated with distilled water and artificial seawater. The ions from the artificial seawater had an effect on zeta potential. Scanning electron microscopy (SEM) images and X-ray diffractograms showed halite in the samples of forsterite-91 mixed with artificial seawater. The presence of halite or adsorption of ions on the surface of forsterite-91 could affect the synthesis of magnetite and hydrocarbons in hydrothermal vents, due to a decrease in the dissolution rates of forsterite-91. The dissolution of forsterite-91 yields low concentrations of Fe(III) and Mn(II) as detected by electron paramagnetic resonance (EPR) spectroscopy. Microanalysis of forsterite-91 showed a higher amount of Mn, with an oxidation that was likely not + II, as Mn in supernatant solutions was only detected by EPR spectroscopy after mixing with artificial seawater at pH 2.0. As Fe(III) and Mn(II) are catalyst constituents of magnetite and manganese oxide, respectively, their presence is important for synthesis in hydrothermal vents. Etch pits were observed only in the forsterite-91 sample mixed with distilled water at pH 8.0. Na, Cl, S, Ca and K were detected in the samples mixed with artificial seawater by SEM-EDS. Si, Mg, Fe and Al were detected in almost all supernatant samples due to forsterite-91 dissolution. Cr was not dissolved in the experiments, thus Cr in the mineral could serve as an effective catalyst for Fischer Tropsch Types (FTT) reactions in hydrothermal vent systems. X-ray diffractograms of the original forsterite-91 also showed peaks arising from zeolites and clinochlore. After the samples were treated with artificial seawater, X-ray diffractograms showed the dissolution of zeolite. Experiments should be performed in the natural environment to verify the potential for zeolites to act as a catalyst in hydrothermal vents.
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| 2. |
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| 3. |
- Holm, Nils, et al.
(författare)
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Reduction of NOx in mafic rocks and abiotic formation of organic nitrogen compounds
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides under the alkaline conditions prevalent in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic organic reactions on Earth. This means that processes leading to the origin of life probably are possible only on planets where some kind of plate tectonics occurs.
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| 4. |
- Holm, Nils, et al.
(författare)
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Reduction of oxidized nitrogen compounds during serpentinization of mafic rocks and prebiotic formation of early life molecules
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors [1]. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides due to phosphorylation by pyrophosphate under the alkaline conditions prevalent in hydrated mantle rocks of the overriding plate [2]. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic organic reactions on Earth. This means that processes leading to the origin of life probably are possible only on planets where some kind of plate tectonics occurs. References: [1] Holm N. G. and Neubeck A. (2009) Geochem T, 10:9. [2] Holm N. G., Dumont M., Ivarsson M., and Konn C. (2006) Geochem T, 7:7.
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| 5. |
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| 6. |
- Lindgren, Paula, et al.
(författare)
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Putative fossil life in a hydrothermal system of the Dellen impact structure, Sweden
- 2010
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Ingår i: International Journal of Astrobiology. - Cambridge : Cambridge University Press. - 1473-5504 .- 1475-3006. ; 9:3, s. 137-146
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Tidskriftsartikel (refereegranskat)abstract
- The role of muscarinic acetylcholine receptors (mAChRs) in regulating glucose uptake in L6 skeletal muscle cells was investigated. [H-3]-2-Deoxyglucose uptake was increased in differentiated L6 cells by insulin, acetylcholine, oxotremorine-M and carbachol. mAChR-mediated glucose uptake was inhibited by the AMPK inhibitor Compound C. Whole cell radioligand binding using [H-3]-N-methyl scopolamine chloride identified mAChRs in differentiated but not undifferentiated L6 cells and M-3 mAChR mRNA was detected only in differentiated cells. M-3 mAChRs are Gq-coupled, and cholinergic stimulation by the rnAChR agonists acetylcholine, oxotremorine-M and carbachol increased Ca2+ in differentiated but not undifferentiated L6 cells. This was due to muscarinic but not nicotinic activation as responses were antagonised by the muscarinic antagonist atropine but not the nicotinic antagonist tubocurarine. Western blotting showed that both carbachol and the AMPK activator AICAR increased phosphorylation of the AMPK alpha subunit at Thr172, with responses to carbachol blocked by Compound C and the CaMKK inhibitor STO609 but not by the PI3K inhibitor wortmannin. AICAR-stimulated AMPK phosphorylation was not sensitive to STO-609, confirming that this compound inhibits CaMKK but not the classical AMPK kinase LKB1. The TAK1 inhibitor (5Z)-7-oxozeaenol and the G(i) inhibitor pertussis toxin both failed to block AMPK phosphorylation in response to carbachol. Using CHO-K1 cells stably expressing each of the mAChR subtypes (M-1-M-4), it was determined that only the M-1 and M-3 mAChRs phosphorylate AMPK, confirming a G(q)-dependent mechanism. This study demonstrates that activation of M-3 mAChRs in L6 skeletal muscle cells stimulates glucose uptake via a CaMKK-AMPK-dependent mechanism, independent of the insulin-stimulated pathway.
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| 7. |
- Neubeck, Anna, et al.
(författare)
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Formation of H(2) and CH(4) by weathering of olivine at temperatures between 30 and 70 degrees C
- 2011
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Ingår i: Geochemical Transactions. - : BioMed Central / Chemistry Central. - 1467-4866. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Hydrocarbons such as CH(4) are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100 degrees C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH(4) through its redox lowering and water splitting properties. Knowledge about the CH(4) and H(2) formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH(4) and for CO(2) sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH(4) and H(2) formation potential of forsteritic olivine. The results show low temperature CH(4) production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH(4) source trapped in the crystal structure of the olivine showed no signs of incorporated CH(4). Also, the available sources of organic carbon were not enough to support the total amount of CH(4) detected in our experiments. There was also a linear relationship between silica release into solution and the net CH(4) accumulation into the incubation bottle headspaces suggesting that CH(4) formation under these conditions could be a qualitative indicator of olivine dissolution. less thanbrgreater than less thanbrgreater thanIt is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH(4), because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH(4) formation both on Earth and on other terrestrial bodies.
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| 8. |
- Neubeck, Anna, et al.
(författare)
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Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C
- 2011
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Ingår i: Geochemical Transactions. - : Springer Science and Business Media LLC. - 1467-4866. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.
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| 9. |
- Neubeck, Anna, 1974-
(författare)
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Low temperature olivine alteration ; an experimental approach
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Water reacting with minerals to alter or dissolve them is a common phenomenon on Earth, leading to a unique chemical composition of the oceans and continents. The continuous circulation of elements and the chemical reactions between them creates the extraordinary environment prevailing on our Earth today and was probably an important requirement for the onset of life on our planet. Olivine is a mineral with the special property of being unstable at atmospheric pressures and temperatures due to its crystal structure and chemical composition. Hydrous alteration of olivine has the capacity to form molecular hydrogen (H2) and hydrated secondary products concurrent with the release of heat. H2 is considered to be crucial for the deep subsurface biosphere and is capable of reducing oxidized carbon species to CH4 and other hydrocarbons through the so-called Sabatier reaction or Fischer-Tropsch Type reactions which are important when studying the large scale CH4 outgassing on Mars or the CH4 seeps coupled to contemporary terrestrial ophiolites. This thesis investigates the potential abiotic formation of H2 and CH4 at low temperatures and pressures as well as under anoxic conditions but also looks at the potential for sustaining the growth of methanogenic archaea with olivine and water. The results suggest that olivine has the potential to form H2 and fuel the abiotic formation of CH4 at low temperatures and low concentrations of dissolved bicarbonate. At higher bicarbonate concentrations, precipitation of silica and carbonate are suggested to cover the reactive catalytic sites on the olivine surface.
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| 10. |
- Neubeck, Anna, et al.
(författare)
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Olivine alteration and H-2 production in carbonate-rich, low temperature aqueous environments
- 2014
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 96, s. 51-61
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Tidskriftsartikel (refereegranskat)abstract
- Hydrous alteration of olivine is capable of producing molecular hydrogen (H-2) under a wide variety of hydrothermal conditions. Although olivine hydrolysis (i.e., serpentinization) has commonly been assessed at elevated temperatures ( > 100 degrees C), the nature of these reactions in relation to H-2 production at lower temperatures has not been systematically evaluated, especially with regard to carbonate-rich fluids. Specifically, carbonate formation may kinetically infringe on geochemical routes related to serpentinization and H-2 production at lower temperatures. Here time-dependent interactions of solid, liquid, and gaseous phases with respect to olivine hydrolysis in a carbonate-rich solution (20 mM HCO3-) at 30, 50 and 70 degrees C for 315 days is investigated experimentally. Within the first two months, amorphous Si-rich (i.e., talc-like) and carbonate phases precipitated; however, no inhibition of olivine dissolution is observed at any temperature based on surface chemistry analyses. High-resolution surface analyses confirm that precipitates grew as spheroids or vertically to form topographic highs allowing further dissolution of the free olivine surfaces and exposing potential catalysts. Despite no magnetite (Fe3O4) being detected, H-2 increased with time in experiments carried out at 70 degrees C, indicating an alternative coupled route for Fe oxidation and H-2 production. Spectrophotometry analyses show that aqueous Fe(II) is largely converted to Fe(III) potentially integrating into other phases such as serpentine and talc, thus providing a viable pathway for H-2 production. No increase in H-2 production was observed in experiments carried out at 30 and 50 degrees C supporting observations that incorporation of Fe(II) into carbonates occurred faster than the intertwined processes of olivine hydrolysis and Fe(III) oxidation. Overall, carbonate formation is confirmed to be a major influence related to H-2 production in low-temperature serpentinization systems.
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| 11. |
- Tulej, Marek, et al.
(författare)
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CAMAM : A Miniature Laser Ablation Ionisation Mass Spectrometer and Microscope-Camera System for In Situ Investigation of the Composition and Morphology of Extraterrestrial Materials
- 2014
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Ingår i: Geostandards and Geoanalytical Research. - 1639-4488 .- 1751-908X. ; 38:4, s. 441-466
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Tidskriftsartikel (refereegranskat)abstract
- Performance studies of a microscope-camera system (MCS) and a laser ablation/ionisation mass spectrometer (LIMS) instrument (referred to here as a laser mass spectrometer or LMS) are presented. These two instruments were designed independently for in situ analysis of solids on planetary surfaces and will be combined to a single miniature instrument suite for in situ chemical and morphological analysis of surface materials on planetary bodies. LMS can perform sensitive chemical (elemental, isotope and molecular) analyses with spatial resolution close to micrometre-sized grains. It allows for studies with mass resolution (M/M) up to 800 in ablation mode (elemental composition) and up to 1500 in desorption mode (molecular analysis). With an effective dynamic range of at least eight orders of magnitude, sensitive and quantitative measurements can be conducted of almost all elements and isotopes with a concentration larger than a few ppb atoms. Hence, in addition to the major element composition, which is important for the determination of mineralogical constituents of surface materials, trace elements can also be measured to provide information on mineral formation processes. Highly accurate isotope ratio measurements can be used to determine in situ geochronology of sample material and for investigations of various isotope fractionation processes. MCS can conduct optical imagery of mm-sized objects at several wavelengths with micrometre spatial resolution for the characterisation of morphological surface details and to provide insight into surface mineralogy. Furthermore, MCS can help in the selection of sample surface areas for further mass spectrometric analysis of the chemical composition. Surface auto-fluorescence measurements and images in polarised light are additional capabilities of the MCS, to identify either fluorescing minerals or organic materials, if present on the analysed surface, for further investigation by LMS. The results obtained by investigations of NIST reference materials, amino acid films and a natural graphite sample embedded in silicate rock are presented to illustrate the performance of the instruments and their potential to deliver chemical information for mineral and organic phases in their geological context.
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| 12. |
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