Correlated analysis of chemical variations with spectroscopic features of the K–Na jarosite solid solutions relevant to Mars

2017

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Jarosite is the first definitely discovered ferric sulfate mineral on Mars, indicating a highly acidic environment in Martian history. K‐H3O and Na‐H3O jarosite solid solutions were synthesized under hydrothermal conditions. Phase identifications and chemical compositions were determined by X‐ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. Raman spectra of those two series of jarosite solid solutions show systematic spectral changes with varying alkali content. When chemical ratios of K/(K + H3O), in K‐H3O jarosite solid solutions, increase from 0% to 88%, their Raman peaks exhibit systematic shifts: ν2(SO4)2− (from 424.7 to 434.3 cm−1), ν4(SO4)2‐ (from 619.6 to 623.8 cm−1), ν1(SO4)2‐ (from 1,011.8 to 1,006.1 cm−1) and, ν3(SO4)2− (from 1,165.4 to 1,152.9 cm−1). Near‐infrared and mid‐infrared spectra were also collected for the spectral library of Mars remote‐sensing studies. The detailed chemical and spectroscopic studies of K‐H3O‐Na jarosite solid solutions would contribute to their potential discoveries on Mars by future Mars missions (e.g., Mars 2020 and ExoMars). Copyright © 2017 John Wiley & Sons, Ltd.

Section: Resultsmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Chemical and spectroscopic investigations of K‐H₃O‐Na jarosite solid solutions applicable for Mars explorations

Cao

2017

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Comparative Raman and visible near‐infrared spectroscopic studies of jarosite endmember mixtures and solid solutions relevant to Mars

Liu

Cao

et al. 2017

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The chemical, structural and spectral properties of hydrated sulfate minerals are essential for their potential identifications and better understanding of martian aqueous history. Jarosite is an indicator of wet and acidic conditions on Mars. However, whether jarosites exist as solid solution phases or physical mixtures of endmembers is still an open question. In this study, we focused on comparisons of spectral characteristics (X‐ray diffraction, Raman, Visible and Near‐infrared) between Jarosite Solid Solutions (JSS) and corresponding Jarosite Physical Mixtures (JPM) with different molar ratios of endmembers (i.e. K‐jarosite to Na‐jarosite), in order to quantitatively characterize their spectral differences and mixing effects. For both X‐ray diffraction and Raman spectra, we find JPM have more overlapped peaks than JSS due to physical mixing effects of the formers, and the relative intensity of the overlapped peaks in K–Na JPM is relevant to the percentage of endmembers. On the other hand, JSS and JPM have strikingly similar Visible and Near‐infrared spectral features except the absorption features at 1950 and 2225 nm, where JPM have larger absorption depth. The detailed spectra properties of these two series of jarosite samples would provide a valuable database for current orbital remote sensing detections and future in situ Raman investigations on Mars (e.g. ExoMars and Mars 2020). Copyright © 2017 John Wiley & Sons, Ltd.

Laboratory Raman and VNIR spectroscopic studies of jarosite and other secondary mineral mixtures relevant to Mars

Liu

Zhang

et al. 2019

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Jarosite is an indicator of ephemeral, acidic fluids in Martian history, which often occurs with some other secondary minerals based on Mars in situ and remote sensing detections. However, detailed Raman and visible and near‐infrared (VNIR) spectroscopic studies of jarosite and other secondary mineral mixtures relevant to Mars still lack, which are essential for jarosite identifications and hence a better understanding of Martian aqueous history. In this study, we prepared 44 binary mixtures of jarosite with four other secondary minerals (alunite, gypsum, kaolinite, and montmorillonite), and characterized their detailed Raman and VNIR spectral features. We find the Raman spectral patterns of jarosite, alunite and gypsum are distinctive and ready for their identification in mixtures, although mixtures with montmorillonite and kaolinite show high fluorescence background and their Raman spectral features are obscured by strong and sharp peaks of jarosite. The normalizing strengths of their characteristic Raman spectral features (e.g., ν1 for jarosite) change with jarosite mass fractions, and mineral distribution maps and volume percentages of endmembers are acquired using Raman imaging method. The band depths of absorption features in VNIR spectra are also correlated with jarosite mass proportions, and four models are proposed to evaluate jarosite mass fractions in the mixtures using a partial least squares algorithm. These detailed spectral properties of mixtures and models would provide valuable information for in situ Raman investigations on Mars (e.g., ExoMars and Mars 2020) and orbital VNIR remote sensing detections (e.g., Compact Reconnaissance Imaging Spectrometer for Mars).