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Melissa D. Lane - One of the best experts on this subject based on the ideXlab platform.
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Sulfates on Mars: Indicators of Aqueous Processes
2020Co-Authors: Janice L. Bishop, Melissa D. Lane, M. Darby Dyar, Adrian J. BrownAbstract:Recent analyses by MER instruments at Meridiani Planum and Gusev crater and the OMEGA instrument on Mars Express have provided detailed information about the presence of Sulfates on Mars [1,2,3]. We are evaluating these recent data in an integrated multi-disciplinary study of visible-near-infrared, mid-IR and Mossbauer spectra of several Sulfate Minerals and Sulfate-rich analog sites. Our analyses suggest that hydrated iron Sulfates may account for features observed in Mossbauer and mid-IR spectra of Martian soils [4]. The Sulfate Minerals kieserite, gypsum and other hydrated Sulfates have been identified in OMEGA spectra in the layered terrains in Valles Marineris and Terra Meridiani [2]. These recent discoveries emphasize the importance of studying Sulfate Minerals as tracers of aqueous processes. The Sulfate-rich rock outcrops observed in Meridiani Planum may have formed in an acidic environment similar to acid rock drainage environments on Earth [5]. Because microorganisms typically are involved in the oxidation of sulfides to Sulfates in terrestrial sites, Sulfate-rich rock outcrops on Mars may be a good location to search for evidence of past life on that planet. Whether or not life evolved on Mars, following the trail of Sulfate Minerals will lead to a better understanding of aqueous processes and chemical weathering.
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Sulfates on Mars as Markers of Aqueous Processes: An Integrated Multidisciplinary Study of Minerals, Mars Analog sites and Recent Mission Data
2020Co-Authors: Janice L. Bishop, Melissa D. Lane, M. D. Dyar, Adrian J. Brown, Mario ParenteAbstract:Our analyses of Sulfate Minerals, analog sites, and Martian spectra and spectral images is focused on characterization of the Martian surface and in particular identification of aqueous processes there.
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Thermal Emission Spectroscopy of Sulfates: Possible Hydrous Iron-Sulfate in the Soil at the MER-A Gusev Crater Landing Site
2020Co-Authors: Melissa D. LaneAbstract:Sulfates are likely to be present on Mars as indicated by the sulfur abundances measured at the Viking and Pathfinder landing sites (approx. 5-10% by weight SO3) [1-3] and because of Mars strongly oxidizing environment. Telescopic observations of Mars tentatively identified weak Sulfate bands in near infrared [4] and thermal infrared [5] data. The currently orbiting midinfrared instruments (TES, THEMIS) and the Mini-TES on the Mars Exploration Rover landers may enable a positive identification [6] and determination of the chemistry of the Sulfates. Critically important to the identification of these Minerals is the presence of their spectra in a spectral library. There exist approximately 370 Sulfate-mineral species [7]. Sulfate Minerals occur in volcanic, hydrothermal, evaporitic, and chemical-weathering environments.
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Integrated spectroscopic studies of anhydrous Sulfate Minerals
2020Co-Authors: Melissa D. Lane, M. Darby Dyar, Janice L. Bishop, Edward A. Cloutis, Ferenc L. Forray, Takahiro HiroiAbstract:Sulfates have been identified in Martian soils and bedrock and are emerging as an important indicator for aqueous activity on Mars. Sulfate Minerals can form in a variety of low-temperature (evaporitic; chemical-weathering) and high-temperature (volcanic/fumarolic; hydrothermal) environments and their formational environments can range from alkaline to acidic. Although Sulfates generally form in the presence of water, not all Sulfates are hydrous or contain water in their structures. Many of these anhydrous Sulfates (Dana group 28; Strunz class 67A) are Minerals that form as accompanying phases to the main Minerals in ore deposits or as replacement deposits in sedimentary rocks. However, some form from thermal decomposition of OH or H2O-bearing Sulfates, such as from the reaction [1]: jarosite = yavapaiite + Fe2O3 + H2O. Where known, the stability fields of these Minerals all suggest that they would be stable under martian surface conditions [2]. Thus, anhydrous Sulfate Minerals may contribute to martian surface mineralogy, so they must be well-represented in spectral libraries used for interpretation of the Martian surface. We present here the preliminary results of an integrated study of emittance, reflectance, and Mossbauer spectroscopy of a suite of wel-lcharacterized anhydrous Sulfates.
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Spectral identification of hydrated Sulfates on Mars and comparison with acidic environments on Earth
International Journal of Astrobiology, 2020Co-Authors: Janice L. Bishop, Melissa D. Lane, M. Darby Dyar, Jillian F. BanfieldAbstract:We interpret recent spectral data of Mars collected by the Mars Exploration Rovers to contain substantial evidence of Sulfate Minerals and aqueous processes. We present visible/near-infrared (VNIR), mid-IR and Mossbauer spectra of several iron Sulfate Minerals and two acid mine drainage (AMD) samples collected from the Iron Mountain site and compare these combined data with the recent spectra of Mars. We suggest that the Sulfates on Mars are produced via aqueous oxidation of sulfides known to be present on Mars from Martian meteorites. The Sulfate-rich rock outcrops observed in Meridiani Planum may have formed in an acidic environment similar to AMD environments on Earth. Because microorganisms are typically involved in the oxidation of sulfides to Sulfates in terrestrial AMD sites, Sulfate-rich rock outcrops on Mars may be a good location to search for evidence of life on that planet. Whether or not life evolved on Mars, following the trail of Sulfate Minerals is likely to lead to aqueous processes and chemical weathering. Our results imply that Sulfate Minerals formed in Martian soils via chemical weathering, perhaps over very long time periods, and that Sulfate Minerals precipitated following aqueous oxidation of sulfides to form the outcrop rocks at Meridiani Planum.
D Lowry - One of the best experts on this subject based on the ideXlab platform.
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sulfur isotope analysis of sulfide and Sulfate Minerals by continuous flow isotope ratio mass spectrometry
Analytical Chemistry, 2001Co-Authors: Nathalie Grassineau, D P Mattey, D LowryAbstract:A continuous flow method (CF-IRMS) for the rapid determination of the sulfur isotope composition of sulfide and Sulfate Minerals has significant advantages over the classic extraction method in terms of the reduced sample quantity and a rapid analytical cycle of less than 8 min/analysis. For optimum performance, the technique is sensitive to a number of operating parameters, including sample weight and the O2 saturation of the Cu-reduction reactor. Raw data are corrected using a calibration based on five international and internal standards ranging from −17.3 to +20.3‰, which requires monitoring in order to correct the effect of changing δ18O of the sample gas on the measured mass 66 values. Measured sulfur contents are within 1−1.5% of expected values and the reproducibility of δ34S values is ±0.1‰ (1σ). The technique has been used successfully for more than 1000 analyses of geological samples with a wide range of δ34S from −20 to +20‰.
Janice L. Bishop - One of the best experts on this subject based on the ideXlab platform.
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Sulfates on Mars: Indicators of Aqueous Processes
2020Co-Authors: Janice L. Bishop, Melissa D. Lane, M. Darby Dyar, Adrian J. BrownAbstract:Recent analyses by MER instruments at Meridiani Planum and Gusev crater and the OMEGA instrument on Mars Express have provided detailed information about the presence of Sulfates on Mars [1,2,3]. We are evaluating these recent data in an integrated multi-disciplinary study of visible-near-infrared, mid-IR and Mossbauer spectra of several Sulfate Minerals and Sulfate-rich analog sites. Our analyses suggest that hydrated iron Sulfates may account for features observed in Mossbauer and mid-IR spectra of Martian soils [4]. The Sulfate Minerals kieserite, gypsum and other hydrated Sulfates have been identified in OMEGA spectra in the layered terrains in Valles Marineris and Terra Meridiani [2]. These recent discoveries emphasize the importance of studying Sulfate Minerals as tracers of aqueous processes. The Sulfate-rich rock outcrops observed in Meridiani Planum may have formed in an acidic environment similar to acid rock drainage environments on Earth [5]. Because microorganisms typically are involved in the oxidation of sulfides to Sulfates in terrestrial sites, Sulfate-rich rock outcrops on Mars may be a good location to search for evidence of past life on that planet. Whether or not life evolved on Mars, following the trail of Sulfate Minerals will lead to a better understanding of aqueous processes and chemical weathering.
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Sulfates on Mars as Markers of Aqueous Processes: An Integrated Multidisciplinary Study of Minerals, Mars Analog sites and Recent Mission Data
2020Co-Authors: Janice L. Bishop, Melissa D. Lane, M. D. Dyar, Adrian J. Brown, Mario ParenteAbstract:Our analyses of Sulfate Minerals, analog sites, and Martian spectra and spectral images is focused on characterization of the Martian surface and in particular identification of aqueous processes there.
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Integrated spectroscopic studies of anhydrous Sulfate Minerals
2020Co-Authors: Melissa D. Lane, M. Darby Dyar, Janice L. Bishop, Edward A. Cloutis, Ferenc L. Forray, Takahiro HiroiAbstract:Sulfates have been identified in Martian soils and bedrock and are emerging as an important indicator for aqueous activity on Mars. Sulfate Minerals can form in a variety of low-temperature (evaporitic; chemical-weathering) and high-temperature (volcanic/fumarolic; hydrothermal) environments and their formational environments can range from alkaline to acidic. Although Sulfates generally form in the presence of water, not all Sulfates are hydrous or contain water in their structures. Many of these anhydrous Sulfates (Dana group 28; Strunz class 67A) are Minerals that form as accompanying phases to the main Minerals in ore deposits or as replacement deposits in sedimentary rocks. However, some form from thermal decomposition of OH or H2O-bearing Sulfates, such as from the reaction [1]: jarosite = yavapaiite + Fe2O3 + H2O. Where known, the stability fields of these Minerals all suggest that they would be stable under martian surface conditions [2]. Thus, anhydrous Sulfate Minerals may contribute to martian surface mineralogy, so they must be well-represented in spectral libraries used for interpretation of the Martian surface. We present here the preliminary results of an integrated study of emittance, reflectance, and Mossbauer spectroscopy of a suite of wel-lcharacterized anhydrous Sulfates.
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Spectral identification of hydrated Sulfates on Mars and comparison with acidic environments on Earth
International Journal of Astrobiology, 2020Co-Authors: Janice L. Bishop, Melissa D. Lane, M. Darby Dyar, Jillian F. BanfieldAbstract:We interpret recent spectral data of Mars collected by the Mars Exploration Rovers to contain substantial evidence of Sulfate Minerals and aqueous processes. We present visible/near-infrared (VNIR), mid-IR and Mossbauer spectra of several iron Sulfate Minerals and two acid mine drainage (AMD) samples collected from the Iron Mountain site and compare these combined data with the recent spectra of Mars. We suggest that the Sulfates on Mars are produced via aqueous oxidation of sulfides known to be present on Mars from Martian meteorites. The Sulfate-rich rock outcrops observed in Meridiani Planum may have formed in an acidic environment similar to AMD environments on Earth. Because microorganisms are typically involved in the oxidation of sulfides to Sulfates in terrestrial AMD sites, Sulfate-rich rock outcrops on Mars may be a good location to search for evidence of life on that planet. Whether or not life evolved on Mars, following the trail of Sulfate Minerals is likely to lead to aqueous processes and chemical weathering. Our results imply that Sulfate Minerals formed in Martian soils via chemical weathering, perhaps over very long time periods, and that Sulfate Minerals precipitated following aqueous oxidation of sulfides to form the outcrop rocks at Meridiani Planum.
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mid infrared emission spectroscopy and visible near infrared reflectance spectroscopy of fe Sulfate Minerals
American Mineralogist, 2015Co-Authors: Melissa D. Lane, Takahiro Hiroi, Stanley A. Mertzman, Penelope L. King, David L Bish, Janice L. Bishop, Darby M Dyar, Deanne A RogersAbstract:Sulfate Minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of Sulfate Minerals on Mars, including Fe-rich Sulfates on the iron-rich planet. Each individual Fe-Sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe 2+ Sulfates are typically more water soluble than Fe 3+ Sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe 3+ Sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-Sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm −1 ; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron Sulfate Minerals. Mid-infrared vibrational modes (for SO 4 , OH, H 2 O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H 2 O, and SO 4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-Sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-Sulfate Minerals are identified.
Penelope L. King - One of the best experts on this subject based on the ideXlab platform.
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mid infrared emission spectroscopy and visible near infrared reflectance spectroscopy of fe Sulfate Minerals
American Mineralogist, 2015Co-Authors: Melissa D. Lane, Takahiro Hiroi, Stanley A. Mertzman, Penelope L. King, David L Bish, Janice L. Bishop, Darby M Dyar, Deanne A RogersAbstract:Sulfate Minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of Sulfate Minerals on Mars, including Fe-rich Sulfates on the iron-rich planet. Each individual Fe-Sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe 2+ Sulfates are typically more water soluble than Fe 3+ Sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe 3+ Sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-Sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm −1 ; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron Sulfate Minerals. Mid-infrared vibrational modes (for SO 4 , OH, H 2 O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H 2 O, and SO 4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-Sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-Sulfate Minerals are identified.
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Mid-infrared emission spectroscopy and visible/near-infrared reflectance spectroscopy of Fe-Sulfate Minerals
American Mineralogist, 2014Co-Authors: Melissa D. Lane, Takahiro Hiroi, Stanley A. Mertzman, Penelope L. King, M. Darby Dyar, David L Bish, Janice L. Bishop, A. Deanne RogersAbstract:Sulfate Minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of Sulfate Minerals on Mars, including Fe-rich Sulfates on the iron-rich planet. Each individual Fe-Sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe 2+ Sulfates are typically more water soluble than Fe 3+ Sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe 3+ Sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-Sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm −1 ; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron Sulfate Minerals. Mid-infrared vibrational modes (for SO 4 , OH, H 2 O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H 2 O, and SO 4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-Sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-Sulfate Minerals are identified.
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Methods to analyze metastable and microparticulate hydrated and hydrous iron Sulfate Minerals
American Mineralogist, 2011Co-Authors: Brendt C. Hyde, Penelope L. King, M. D. Dyar, M. SpildeAbstract:We evaluate analytical methods for characterizing hydrated and hydrous iron Sulfate Minerals (HHIS) that are typically metastable in air or vacuum, commonly form micrometer-sized particles, and contain multi-valent and light elements (Fe 2+ , Fe 3+ , OH − , and H 2 O) that may be challenging to quantify. We synthesized or obtained HHIS—szomolnokite, melanterite, rhomboclase, schwertmannite, ferricopiapite, paracoquimbite, and jarosite—as well as Fe-oxides. These nominally pure samples were characterized with X-ray diffraction (XRD), and then used to evaluate bulk analyses obtained from combined inductively coupled plasma, optical emission spectroscopy (ICP-OES), ion chromatography (IC), Mossbauer spectroscopy, and mass spectrometry. Integrated bulk analyses showed excellent agreement with the nominal formulas for the Minerals. Because HHIS commonly form micro-sized particles—for example, HHIS found in acid mine drainage (AMD) environments and in martian meteorites—it is necessary to develop micro-analytical techniques. Microscopic mid-infrared spectroscopy allows the analyst to successfully discriminate among HHIS with minimal sample preparation on the small scale (~40 × 40 μm). For chemical analysis, electron probe microanalysis (EPMA) is preferred for samples that can be mounted, polished, coated, and that are stable under high vacuum; however, few HHIS meet those criteria. To characterize HHIS compositions, we show that multiple low-vacuum scanning electron microscopy (SEM) analyses of the same uncoated, unpolished mineral are required. Analysis of each mineral shows linear trends on ternary diagrams of 5×Fe-SO 4 -O (where oxygen is in O, OH, and H 2 O) that may be used to narrow down the HHIS mineralogy. Low-vacuum SEM also provides invaluable information about the geochemical and textural context of the samples. Our study provides protocols for microanalysis of these challenging, fine-grained, and metastable HHIS that may also be applied to other mineral groups.
David L Bish - One of the best experts on this subject based on the ideXlab platform.
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mid infrared emission spectroscopy and visible near infrared reflectance spectroscopy of fe Sulfate Minerals
American Mineralogist, 2015Co-Authors: Melissa D. Lane, Takahiro Hiroi, Stanley A. Mertzman, Penelope L. King, David L Bish, Janice L. Bishop, Darby M Dyar, Deanne A RogersAbstract:Sulfate Minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of Sulfate Minerals on Mars, including Fe-rich Sulfates on the iron-rich planet. Each individual Fe-Sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe 2+ Sulfates are typically more water soluble than Fe 3+ Sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe 3+ Sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-Sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm −1 ; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron Sulfate Minerals. Mid-infrared vibrational modes (for SO 4 , OH, H 2 O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H 2 O, and SO 4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-Sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-Sulfate Minerals are identified.
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Mid-infrared emission spectroscopy and visible/near-infrared reflectance spectroscopy of Fe-Sulfate Minerals
American Mineralogist, 2014Co-Authors: Melissa D. Lane, Takahiro Hiroi, Stanley A. Mertzman, Penelope L. King, M. Darby Dyar, David L Bish, Janice L. Bishop, A. Deanne RogersAbstract:Sulfate Minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of Sulfate Minerals on Mars, including Fe-rich Sulfates on the iron-rich planet. Each individual Fe-Sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe 2+ Sulfates are typically more water soluble than Fe 3+ Sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe 3+ Sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-Sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm −1 ; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron Sulfate Minerals. Mid-infrared vibrational modes (for SO 4 , OH, H 2 O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H 2 O, and SO 4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-Sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-Sulfate Minerals are identified.
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Stability of Mg-Sulfate Minerals in the presence of smectites: Possible mineralogical controls on H2O cycling and biomarker preservation on Mars
Geochimica et Cosmochimica Acta, 2012Co-Authors: Siobhan A. Wilson, David L BishAbstract:Abstract Martian layered deposits and regolith at Gale Crater may contain multiple hydrated mineral phases, tentatively identified as hydrated Mg-Sulfate Minerals and smectites. We have used humidity buffer experiments to assess the stability of hydrated Mg-Sulfate Minerals in the presence of smectites in order to improve our understanding of the probable behavior of Mg-Sulfate Minerals within multiphase geological materials on Mars. A series of long-term experiments employed temperature (−25 to +23 °C) and relative humidity (RH) conditions (7–100%) that emulate near-equatorial martian surface conditions. Our results indicate that the hydration state of Mg-Sulfate Minerals is affected by the presence of RH-sensitive clay Minerals (i.e., smectites). The formation of gypsum and bassanite in dry mineral mixtures via cation exchange between Ca-bearing smectite and Mg-Sulfate Minerals indicates that Ca-Sulfate Minerals may be useful indicators of H 2 O and metal mobility at Mars-relevant temperatures (−25 to +23 °C). The presence of smectites also suppresses deliquescence of Mg-Sulfate Minerals at 100% RH and low, but non-freezing, temperatures. Co-existence of smectites and Mg-Sulfate Minerals appears to buffer RH within mixtures of these Minerals, which can result in production or preservation of Mg-Sulfate phases that are inconsistent with measured values of atmospheric RH. Consequently, hydrated Mg-Sulfate Minerals may persist beyond their expected T –RH equilibrium fields on longer timescales within smectite–MgSO 4 mixtures than in the pure MgSO 4 –H 2 O system. Dehydration of highly hydrated Mg-Sulfate Minerals appears to slow in the presence of smectite, which may have important implications for long-term preservation of organic biosignatures within Mg-Sulfate crystals on Mars. Together, these observations suggest that Mg-Sulfate mineral behavior (and thus cycling and bioavailability of H 2 O and metals) may be impacted by the presence of smectites within mineralogically complex martian layered deposits and regolith.
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Formation of gypsum and bassanite by cation exchange reactions in the absence of free‐liquid H2O: Implications for Mars
Journal of Geophysical Research, 2011Co-Authors: Siobhan A. Wilson, David L BishAbstract:[1] Smectites and hydrated Mg Sulfate Minerals have been identified in close association at various locations on the Martian surface. The hydration states of Sulfates and smectites are dependent on temperature and relative humidity (RH), and therefore these Minerals have the potential to affect cycling and bioavailability of H2O on Mars. We have conducted X-ray powder diffraction experiments to investigate cycling of H2O within mixtures of Ca-bearing smectites and hydrated Mg Sulfate Minerals under conditions of varying RH similar to those that exist at or just beneath the Martian surface. Our experiments show that under conditions of varying RH, cation-exchange reactions occur between these two potential components of the Martian regolith, producing gypsum [CaSO4·2H2O] and bassanite [CaSO4·∼0.5H2O] in the absence of free-liquid H2O. Cation-exchange reactions were accompanied by significant loss of porosity, warping of the sample surface and, in some cases, volume expansion. The formation of Ca Sulfate Minerals in these experiments provides evidence for the development of thin films of H2O at mineral surfaces and suggests that similar processes may operate at the arid surface of Mars. Humidity-driven cation-exchange reactions between smectites and hydrated Mg Sulfate Minerals may therefore play a role in shaping the present-day Martian surface and could have provided a transient source of H2O and nutrients (e.g., major and trace elements and possibly organic micro/macronutrients) for putative microorganisms.
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USE OF THE PROTOTYPE CHEMIN XRD/XRF INSTRUMENT IN ANALYZING COMPLEX MIXTURES OF POTENTIAL MARTIAN Sulfate Minerals
1998Co-Authors: D. Vaniman, David L Bish, David F. Blake, S. Collins, Steve J. Chipera, P. Sarrazin, S. T. ElliottAbstract:MIXTURES OF POTENTIAL MARTIAN Sulfate Minerals. D. Vaniman, D. Bish, D. Blake, S. A. Collins, S. Chipera, P. Sarrazin, and S. T. Elliott, Geology and Geochemistry, MS D462, Los Alamos National Laboratory, Los Alamos, NM 87545, NASA Ames Research Center, Mail Stop 239-4, Moffett Field, CA 94035, Detector Advanced Development, 300-315, Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109