¹Naoki Hirakawa,¹Yoko Kebukawa,¹Kensei Kobayashi,²Hideyuki Nakano
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114167]
¹Graduate School of Engineering Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
²Faculty of Culture and Sport Policy, Toin University of Yokohama, 1614 Kurogane-cho, Aoba-ku, Yokohama 225-8503, Japan
Copyright Elsevier

Molecular structures and chemical compositions of organic matter in primitive meteorites reflect the conditions of the parent bodies, as well as the preaccretional history. During the parent body processing, co-existing minerals could have effects on structural changes of organics, in addition to temperature and redox state. Here, we performed heating experiments of a primordial organic matter analog with and without minerals to understand the effects of minerals on organic matter in conditions simulating metamorphism in thermally metamorphosed type 3 chondrites. The primordial analog materials were heated up to 400 °C, and the experimental products were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and gas chromatography mass spectrometry (GC/MS). Montmorillonite and olivine, particularly montmorillonite, enhanced decomposition of oxygen containing species due to decarboxylation and/or cracking, while olivine enhanced esterification at lower temperature. Our results further imply that the variations of insoluble organic matter in CV, CO, and type 3 ordinary chondrites could be partially due to different mineral compositions. We also tested the effects of pressure on the degradation of the organic matter at 400 °C up to 268 atm, however no significant pressure effects were observed by FTIR and GC/MS.

^1,2J.Pape,¹Å.V.Rosén,¹K.Mezger,³M.Guillong
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.10.019]
¹Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland
²Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland
Copyright Elsevier

Chondrules from unequilibrated ordinary chondrites are among the oldest Solar system materials and preserve mineralogical, chemical and isotopic signatures that link them to their primary formation mechanisms and environments in the early Solar System. Some chondrules record features indicating modifications by high- to low-temperature processes throughout their residence time in the protoplanetary disk. Chondrules that were partially modified after their primary formation record chemical, isotopic and textural information on their initial formation conditions and subsequent reprocessing that are essential to reconstruct their formation environments and interpret the ages recorded by individual chondrules correctly.

The detailed textural and major, minor and trace element analyses of two type-I chondrules from the low petrologic type ordinary chondrites MET 00526 and MET 00452 (L/LL3.05) reveal complex chemical and textural systematics bearing testimony of their multi-stage high temperature evolution, including reheating and partial remelting, in the evolving protoplanetary disk prior to accretion into their parent bodies. During primary crystallization of chondrule MET00526_Ch43, mineral growth, including incipient formation of feldspar in the outer parts of the chondrule, led to the fractionation of melt, eventually resulting in a chemical gradient in the mesostasis. During a later punctuated reheating that ultimately led to partial remelting of the outer parts of the chondrule, mesostasis and low-Ca pyroxene remelted partially. This partial remelting enhanced the chemical differences within the mesostasis and led to the formation of two chemically distinct mesostases in the inner and the outer zone of the chondrule with almost complementary abundances of Rb, Na, K, Ba, Sr and Eu. The calculated bulk mesostasis composition reveals chondritic relative abundances of these elements in the bulk chondrule with a slight depletion of the most volatile elements. Chemical and textural observations further indicate that this disequilibrium remelting occurred under more reducing conditions than the primary melting event preserved in the chondrule centre, allowing for the crystallization of a second generation of low-Ca pyroxene in the outer parts of the chondrule. Very similar processes are also recorded in chondrule MET00452_Ch22 with the degree of remelting being more extensive.

A previously determined young 26Al-26Mg age of ∼3 Ma after CAIs determined for chondrule MET00452_Ch22 dates the time of the chondrule remelting rather than its primary formation. This is evidence for a late thermal event in the protoplanetary disk and generally indicates that multiple, distinct thermal pulses occurred in the chondrule forming region of the protoplanetary disk throughout the time of chondrule formation. The nonconcentric secondary outer zone around a spherical inner zone may indicate a directed heat source as the cause of partial remelting and reprocessing of primary chondrules.

¹Zuriñe Yoldi,¹Antoine Pommerol,^1,2Olivier Poch,¹Nicolas Thomas
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114169]
¹Physikalisches Institut, Universität Bern and NCCR PlanetS, Sidlerstrasse 5, 3012 Bern, Switzerland
²Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
Copyright Elsevier

The reflectance of water ice and dust mixtures depends, amongst other parameters, on how the components are mixed (e.g. intimate mixture, areal mixture or coating) (Clark, 1999). Therefore, when inverting the reflectance spectra measured from planetary surfaces to derive the amount of water ice present at the surface, it is critical to distinguish between different mixing modes of ice and dust. However, the distinction between mixing modes from reflectance spectra remains ambiguous. Here we show how to identify some water ice/soil mixing modes from the study of defined spectral criteria and colour analysis of laboratory mixtures. We have recreated ice and dust mixtures and found that the appearance of frost on a surface increases its reflectance and flattens its spectral slopes, whereas the increasing presence of water ice in intimate mixtures mainly impacts the absorption bands. In particular, we provide laboratory data and a spectral anal

^1,2Kohei Fukuda,¹Hajime Hiyagon,³Wataru Fujiya,^4,7Takanori Kagoshima,^1,6Keita Itano,¹Tsuyoshi Iizuka,²Noriko T.Kita,^4,5Yuji Sano
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.10.011]
¹Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
²WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706, USA
³Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
⁴Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
⁵Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, People’s Republic of China
⁶Present address: College of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan
⁷Present address: Department of Environmental Biology and Chemistry, School of Science, University of Toyama, Toyama 930-8555, Japan
Copyright Elsevier

We have performed in situ analyses of Li-Be-B and Al-Mg isotope systematics, and abundances of rare earth elements (REEs) in two Ca-Al-rich inclusions (CAIs) from the Ornans-like carbonaceous chondrite Yamato-81020 (CO3.05). The present CO CAIs are depleted in ultra-refractory heavy REEs (group II REE pattern), suggesting condensation of these CAIs or their precursors from the solar nebula. Initial 26Al/27Al ratios, (26Al/27Al)0, of these CO CAIs are found to be (4.8 ± 0.5) × 10–5 and (4.9 ± 0.3) × 10–5 (2σ), indicating their contemporaneous formation with a majority of CAIs from CV chondrites. Melilite grains in the present CO CAIs show clear excesses in 10B, ranging from ∼370 to ∼4300‰ relative to the chondritic B isotopic composition, which are correlated well with 9Be/11B ratios. The correlation indicates in situ decay of 10Be in the present CO CAIs and yields initial 10Be/9Be ratios, (10Be/9Be)0, for the individual CAIs of (2.9 ± 0.6) × 10–3 and (2.2 ± 1.0) × 10–3 (2σ), which are significantly greater than the average (10Be/9Be)0 = ∼0.7 × 10–3 recorded in CAIs from Vigarano-like carbonaceous (CV) chondrites. The apparent variation in (10Be/9Be)0 between the CO and CV CAIs, despite having indistinguishable (26Al/27Al)0 of ∼5 × 10–5, provides evidence for heterogeneous distribution of 10Be in the CAI forming-regions at the very beginning of the Solar System. The elevated (10Be/9Be)0 and group II REE patterns in the CO CAIs may reflect that compared with the CV CAIs having unfractionated REEs the present CO CAIs have formed closer to the Sun where 10Be was produced more efficiently through solar cosmic ray irradiation caused by solar flares. Alternatively, if the present CO CAIs and CV CAIs formed in the same region, and 26Al was distributed homogeneously at the CAI-forming region, our results indicate that solar cosmic ray fluxes at the forming region have fluctuated by a factor of six within a short duration (∼0.2 million years) inferred from the Al-Mg chronology.

¹Badyukov, D.D.
Solar System Research 54, 263-274 Link to Article [DOI: 10.1134/S0038094620040024]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991, Russian Federation

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¹Kimura, M.,¹Imae, N.,²Komatsu, M.,³Barrat, J.A.,⁴Greenwood, R.C.,¹Yamaguchi, A.,⁵Noguchi, T.
Polar Science (in Press)  Link to Article [DOI: 10.1016/j.polar.2020.100565]
¹National Institute of Polar Research, Tokyo, 190-8518, Japan
²SOKENDAI, Kanagawa, 240-0193, Japan
³Université de Bretagne Occidentale, Institut Universitaire Europé en de La Mer, CNRS UMR 6538, Place Nicolas Copernic, Plouzané 29280, France
⁴Planetary and Space Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom
⁵Kyushu University, Fukuoka, 819-0395, Japan

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¹Krishnamurthy, P.
Journal of the Geological Society of India 96, 111-147 Link to Article [DOI: 10.1007/s12594-020-1521-1]
¹Department of Atomic Energy, Begumpet, Formerly Atomic Minerals Directorate for Exploration and Research (AMD), Hyderabad, 500 016, India

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¹Blukis, R.,²Pfau, B.,³Günther, C.M.,²Hessing, P.,^2,4Eisebitt, S., Einsle,⁵J.,⁶Harrison, R.J.
Geochemistry, Geophysics, Geosystems 21, e2020GC009044 Link to Article [DOI: 10.1029/2020GC009044]
¹GFZ German Centre for Geosciences, Potsdam, Germany
²Max-Born-Institut, Berlin, Germany
³Center for Electron Microscopy (ZELMI), Technische Universität Berlin, Berlin, Germany
⁴Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin, Germany
⁵School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom
⁶Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom

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¹S.DeAngelis,²F.Tosi,¹C.Carli,²S.Potin,²P.Beck,²O.Brissaud,²B.Schmitt, ¹G.Piccioni,¹M.C.De Sanctis,¹F.Capaccioni
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114165]
¹INAF-IAPS, Institute for Space Astrophysics and Planetology, Via del Fosso del Cavaliere, 100, Rome 00133, Italy
²Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), Grenoble 38058 Cédex 9, France
Copyright Elsevier

Hydrated sodium sulfates have been suggested to be present in variable amounts in Solar System objects such as Mars and Europa, among the possible others. The presence of these hydrated species is related to current/past aqueous environments, thus has an importance regarding the potential habitability of planetary objects. In this study, we analyzed anhydrous sodium sulfate (thénardite) and the hydrated sodium sulfate (mirabilite) by means of visible-infrared reflectance spectroscopy in the 0.4–5 μm spectral range, at different low temperatures between 80 and 298 K. Each mineral has been analyzed in three different grain sizes, between 36 and 150 μm. The anhydrous compound, thénardite, is characterized by a nearly flat spectrum in the visible and near IR up to 2.6 μm, while in the 3–4 μm region, the spectrum shows a few weak features due to H₂O and SO₄²⁻ overtones/combinations. The first strong SO₄²⁻ overtone is visible at 4.6 μm. Spectra of mirabilite are substantially characterized by H₂O absorption features in the 1–3 μm region, and by sulfate overtone/combination bands occurring at 3.8 and 4.7 μm. A weak feature appearing at 2.18 μm is also putatively attributed to the sulfate ion. The bands show changes as a function of temperature. The hydration absorption features in mirabilite show the strongest dependence with temperature, both in terms of shift in position and change of spectral shape. Bands at 3.1–3.24 μm in thénardite, as well as absorption features located at 1.78 and 2.47 μm in mirabilite, could be used as diagnostic proxies for the detection of these two minerals on planetary bodies.

^1,2Honglei Lin,³J.D.Tarnas,³J.F.Mustard,¹Xia Zhang,²Yong Wei,
²Weixing Wan,⁴F.Klein,⁵J.R.Kellner
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114168]
¹Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100101, China
²Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. 100029, China
³Dept. of Earth, Environmental, and Planetary Sciences, Brown University, RI 02912, The United States of America
⁴Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MA 02543, The United States of America
⁵Institute at Brown for Environment and Society, Brown University, RI 02912, The United States of America
Copyright Elsevier

Serpentine and carbonate are products of serpentinization and carbonation processes on Earth, Mars, and other celestial bodies. Their presence implies that localized habitable environments may have existed on ancient Mars. Factor Analysis and Target Transformation (FATT) techniques have been applied to hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to identify possible serpentine and Mg-carbonate-bearing outcrops. FATT techniques are capable of suggesting the presence of individual spectral signals in complex spectral mixtures. Applications of FATT techniques to CRISM data thus far only evaluate whether an entire analyzed image (≈3 × 105 pixels) may contain spectral information consistent with a specific mineral of interest. The spatial distribution of spectral signal from the possible mineral is not determined, making it difficult to validate a reported detection and also to understand the geologic context of any purported detections. We developed a method called Dynamic Aperture Factor Analysis/Target Transformation (DAFA/TT) to highlight the locations in a CRISM observation (or any similar laboratory or remotely acquired data set) most likely to contain spectra of specific minerals of interest. DAFA/TT determines the locations of possible target mineral spectral signals within hyperspectral images by performing FATT in small moving windows with different geometries, and only accepting pixels with positive detections in all cluster geometries as possible detections. DAFA/TT was applied to a hyperspectral image of a serpentinite from Oman for validation testing in a simplified laboratory setting. The mineral distribution determined by DAFA/TT application to the laboratory hyperspectral image was consistent with Raman analysis of the serpentinite sample. DAFA/TT also successfully mapped the spatial distribution of serpentine and Mg-carbonate previously detected in CRISM data using band parameter mapping and extraction of ratioed spectra. We applied DAFA/TT to CRISM images in some olivine-rich regions of Mars to characterize the spatial distribution of serpentine and magnesite outcrops.