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  • 1
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    Mid-infrared spectroscopy of alkali feldspar samples for space application (2020)
    Springer Vienna
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    Publication Date: 2023-06-23
    Description: Feldspars are major components of terrestrial planetary surfaces. For future space application and the setup of a comprehensive reference database, Na- and K-rich alkali feldspars, NaAlSi3O8 – KAlSi3O8, have been investigated by infrared reflectance spectroscopy. We related the feldspar spectra to the chemical composition and state of Al,Si order/disorder. The infrared measurements were analyzed with respect to band shifts and peak shapes using the autocorrelation function. Natural samples served as starting materials. Some samples were treated by the alkali exchange method to produce pure end-members, which were then heated to generate various states of Al,Si disorder. X-ray diffraction (XRD) methods served to determine the Al,Si distribution. Our autocorrelation allowed to differentiate between the compositional and the order/disorder influences seen in the spectra in the wavelength range between 7 μm up to 14 μm (1429 cm− 1 to 714 cm− 1). Space missions often analyze the surfaces of planetary bodies using remote sensing. Therefore, our results are essential to characterize and distinguish alkali feldspars on the surfaces of terrestrial planetary bodies like Mercury.
    Description: Deutsches Zentrum für Luft- und Raumfahrt https://doi.org/10.13039/501100002946
    Keywords: ddc:549 ; Alkali feldspars ; Infrared spectroscopy ; X-ray diffraction ; Al,Si distribution
    Language: English
    Type: doc-type:article
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  • 2
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    Mid‐Infrared Spectroscopy of Feldspars From the Bühl Basalt (Northern Hesse, Germany) Formed Under Reducing Conditions as Terrestrial Analogue of Mercury for MERTIS (2023)
    Details
    Publication Date: 2023-12-19
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The MErcury Radiometer and Thermal Infrared Spectrometer instrument onboard the BepiColombo spacecraft is designed to investigate Mercury’s surface in the mid‐infrared (mid‐IR). Based on MESSENGER data and modeling, Mercury is thought to be evolved under highly reducing conditions (e.g., McCubbin et al., 2017, 〈ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1002/2017JE005367"〉https://doi.org/10.1002/2017JE005367〈/ext-link〉; Namur & Charlier, 2017, 〈ext-link ext-link-type="uri" xlink:href="https://doi.org/10.1038/ngeo2860"〉https://doi.org/10.1038/ngeo2860〈/ext-link〉). The modeling also indicates that Mercury's surface is rich in feldspar. However, it is unknown if reducing conditions during the emplacement of volcanic melts have an influence on the IR properties of feldspars. Therefore, we investigated basaltic samples from the Bühl quarry in northern Hesse, Germany, that evolved under reducing conditions in the mid‐IR and compared the spectra with samples that experienced more oxidizing conditions during their formation. The Bühl samples are feldspar‐rich and contain metallic iron in some areas. Our investigations show that there are no differences between feldspars that formed under different oxidizing conditions. All spectral properties could be explained by well‐known factors that affect mid‐IR spectra of silicates.〈/p〉
    Description: Plain Language Summary: ESA's and Japan Aerospace Exploration Agency’s spacecraft BepiColombo is equipped, beside other instruments, with a thermal infrared (IR) radiometer and spectrometer called MErcury Radiometer and Thermal Infrared Spectrometer (MERTIS). For the accurate interpretation of the data from the MERTIS instrument, laboratory analog material is necessary. This analog material must fulfill different characteristics, such as different chemical and mineralogical compositions. Another not yet studied property is the availability of oxygen during the formation of the minerals. Depending on how much oxygen is available, different minerals form. However, this is an important feature, because Mercury is thought to have evolved under highly reducing conditions, as opposed to Earth where nearly all material formed significant more oxidizing conditions. One phase that is strongly associated with reducing magma formation conditions is metallic iron. There are only few natural outcrops on Earth, were stronger reducing conditions were present so that metallic iron could be formed. One of these outcrops is the Bühl quarry in northern Hesse, Germany. From there we used different samples to analyze the effect of oxygen availability on mid‐IR spectra of plagioclase feldspars.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉We present infrared spectra of basaltic samples from the Bühl, Hesse, Germany in preparation of the MERTIS experiment〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Comparison of feldspars formed at different oxygen fugacities showed no spectral differences〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉This is an important result for MERTIS, which will investigate Mercury that formed under reducing conditions〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: DLR
    Description: http://bc-mertis-pi.uni-muenster.de/
    Keywords: ddc:549 ; infrared reflectance spectroscopy ; feldspars ; Bühl basalt ; reducing conditions ; Mercury ; MERTIS
    Language: English
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  • 3
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    VERITAS: a Discovery-Class Venus Surface Geology and Geophysics Mission (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Our understanding of solar system evolution is limited by a great unanswered question: How Earthlike is Venus? We know that these "twin" planets formed with similar bulk composition and size. Yet the evolutionary path Venus followed has diverged from Earth's, in losing its surface water and becoming hotter than Mercury. What led to this? The answer has profound implications for how terrestrial planets become habitable and the potential for life in the universe.
    Keywords: Lunar and Planetary Science and Exploration; Launch Vehicles and Launch Operations; Exobiology
    Type: Annual IEEE Aerospace Conference 2016; Mar 05, 2016 - Mar 12, 2016; Big Sky, MT; United States
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  • 4
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    Global Inventory and Characterization of Pyroclastic Deposits on Mercury: New Insights into Pyroclastic Activity from MESSENGER Orbital Data (2014)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We present new observations of pyroclastic deposits on the surface of Mercury from data acquired during the orbital phase of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. The global analysis of pyroclastic deposits brings the total number of such identified features from 40 to 51. Some 90% of pyroclastic deposits are found within impact craters. The locations of most pyroclastic deposits appear to be unrelated to regional smooth plains deposits, except some deposits cluster around the margins of smooth plains, similar to the relation between many lunar pyroclastic deposits and lunar maria. A survey of the degradation state of the impact craters that host pyroclastic deposits suggests that pyroclastic activity occurred on Mercury over a prolonged interval. Measurements of surface reflectance by MESSENGER indicate that the pyroclastic deposits are spectrally distinct from their surrounding terrain, with higher reflectance values, redder (i.e., steeper) spectral slopes, and a downturn at wavelengths shorter than approximately 400nm (i.e., in the near-ultraviolet region of the spectrum). Three possible causes for these distinctive characteristics include differences in transition metal content, physical properties (e.g., grain size), or degree of space weathering from average surface material on Mercury. The strength of the near-ultraviolet downturn varies among spectra of pyroclastic deposits and is correlated with reflectance at visible wavelengths. We suggest that this interdeposit variability in reflectance spectra is the result of either variable amounts of mixing of the pyroclastic deposits with underlying material or inherent differences in chemical and physical properties among pyroclastic deposits.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN21209 , Geophysical Research Letters (ISSN 0094-8276); 119; 3; 635–658
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  • 5
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    Mid-infrared reflectance spectroscopy of aubrite components (2021)
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    Publication Date: 2021-07-26
    Description: Aubrites Peña Blanca Spring and Norton County were studied in the mid-infrared reflectance as part of a database for the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument on the ESA/JAXA BepiColombo mission to Mercury. Spectra of bulk powder size fractions from Peña Blanca Spring show enstatite Reststrahlen bands (RB) at 9 µm, 9.3 µm, 9.9 µm, 10.4 µm, and 11.6 µm. The transparency feature (TF) is at 12.7 µm, the Christiansen feature (CF) at 8.1–8.4 µm. Micro-FTIR of spots with enstatite composition in Norton County and Peña Blanca Spring shows four types: Types I and II are similar to the bulk powder spectra but vary in band shape and probably display axis orientation. Type III has characteristic strong RB at 9.2 µm, 10.4 µm, and 10.5 µm, and at 11.3 µm. Type IV is characterized by a strong RB at 10.8−11.1 µm. Types III and IV could show signs of incipient shock metamorphism. Bulk results of this study confirm earlier spectral studies of aubrites that indicate a high degree of homogeneity and probably make the results of this study representative for spectral studies of an aubrite parent body. Spectral types I and II occur in all mineralogical settings (mineral clasts, matrix, melt, fragments in melt vein), while spectral type III was only observed among the clasts, and type IV in the melt. Comparison with surface spectra of Mercury does not obtain a suitable fit, only type IV spectra from quenched impact glass show similarity, in particular the 11 µm feature. Results of this study will be available upon request or via the IRIS database (Münster) and the Berlin Emissivity Database (BED).
    Keywords: 549.112
    Language: English
    Type: article
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  • 6
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    Mid‐Infrared Spectroscopy of Anorthosite Samples From Near Manicouagan Crater, Canada, as Analogue for Remote Sensing of Mercury and Other Terrestrial Solar System Objects (2021)
    Details
    Publication Date: 2022-03-22
    Description: We investigated mid‐infrared reflectance spectra of anorthosite samples from Mt. Briand near the Manicouagan impact structure. Microprobe analyses of the plagioclase minerals reveal that they have a similar chemical composition (labradoritic), which is corroborated by the location of the Christiansen Feature at around 7.96 μm (1256 cm−1). However, their respective spectral shapes differ from each other in the region of the reststrahlen bands. This is linked to the degree of Al,Si order within the plagioclase minerals, which also correlates with the previously assumed distance of the sample site to the impact melt. Powdering and sieving led to remarkable changes in the spectra resulting from different mechanical stability of minerals contained in the sample. Our data show that even very weakly shocked (6–10 GPa, shockstage S2) anorthosites could show spectra of Al,Si disordered plagioclase which we attribute to post shock heating after the impact shock. Consequently, the degree of Al,Si order has to be taken into account in the interpretation of remote sensing data. A comparison of synthetic linear mixture with an average Mercury spectrum reveals the possible presence of more or less anorthositic material with reduced degree of Al,Si order of the plagioclase component on Mercury's surface. The results of our study are helpful for the interpretation of data returned by space missions, especially for MERTIS ‐ an infrared spectrometer on its way to Mercury.
    Description: Plain Language Summary: The studied rocks, which contain predominantly the feldspar mineral plagioclase, are very common in our Solar System, for example, on the Moon and probably also on Mercury. The surface of planets without atmosphere, like Moon and Mercury are constantly the target of asteroid impacts. These impacts cause changes in the constituents of the rocks. The studied samples are from the area near a meteorite crater and show weak effects of the former meteorite impact. The infrared spectra of the samples have different shapes. This shape does not correlate with the chemical composition, but with the distribution of aluminum and silicon ions in the plagioclase components of the investigated samples. This distribution is often underestimated in remote sensing. Our study shows that this distribution of these ions is related to a previously assumed distance of the sample location from the impact. The results are useful for interpreting remote sensing data coming back from space missions. In our case, in particular, from an infrared spectrometer on its way to the planet Mercury called MERTIS. The study also presents a spectrum calculated from various mineral spectra comparable to the samples analyzed. This spectrum shows similarities to an average Mercury surface spectrum and suggests that the feldspars on the Mercury surface have a very disordered ion distribution.
    Description: Key Points: Low impact shock with proposed impact melt influences Al,Si order of plagioclases. Grinding of rocks leads to modal changes of the minerals. Potential plagioclases with reduced degree of Al,Si order on the surface of Mercury.
    Description: Deutsches Zentrum für Luft‐ und Raumfahrt (DLR) http://dx.doi.org/10.13039/501100002946
    Language: English
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