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.

¹Shelby L. Lyons,¹Allison T. Karp,¹Timothy J. Bralower,²Kliti Grice,
²Bettina Schaefer,^3,4,5Sean P. S. Gulick,⁶Joanna V. Morgan,⁶Katherine H. Freeman
Proceedings of the National Academy of Sciences of teh United States of America (in Press) Link to Article [https://doi.org/10.1073/pnas.2004596117]
¹Department of Geosciences, The Pennsylvania State University, University Park, PA 16802;
²Western Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth, WA 6102, Australia;
³Institute for Geophysics, University of Texas at Austin, Austin, TX 78758;
⁴Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712;
⁵Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX 78712;
⁶Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, United Kingdom

An asteroid impact in the Yucatán Peninsula set off a sequence of events that led to the Cretaceous–Paleogene (K–Pg) mass extinction of 76% species, including the nonavian dinosaurs. The impact hit a carbonate platform and released sulfate aerosols and dust into Earth’s upper atmosphere, which cooled and darkened the planet—a scenario known as an impact winter. Organic burn markers are observed in K–Pg boundary records globally, but their source is debated. If some were derived from sedimentary carbon, and not solely wildfires, it implies soot from the target rock also contributed to the impact winter. Characteristics of polycyclic aromatic hydrocarbons (PAHs) in the Chicxulub crater sediments and at two deep ocean sites indicate a fossil carbon source that experienced rapid heating, consistent with organic matter ejected during the formation of the crater. Furthermore, PAH size distributions proximal and distal to the crater indicate the ejected carbon was dispersed globally by atmospheric processes. Molecular and charcoal evidence indicates wildfires were also present but more delayed and protracted and likely played a less acute role in biotic extinctions than previously suggested. Based on stratigraphy near the crater, between 7.5 × 1014 and 2.5 × 1015 g of black carbon was released from the target and ejected into the atmosphere, where it circulated the globe within a few hours. This carbon, together with sulfate aerosols and dust, initiated an impact winter and global darkening that curtailed photosynthesis and is widely considered to have caused the K–Pg mass extinction.

¹Ke Zhu,¹Frédéric Moynier,²Martin Schiller,³ConelM. O’D. Alexander,⁴Jean-Alix Barrat,⁵Addi Bischoff,^1,2Martin Bizzarro
Geochimica et Cosmochimcia Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.10.007]
¹Institut de Physique du Globe de Paris, Université de Paris, CNRS UMR 7154, 1 rue Jussieu, Paris F-75005, France
²Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5–7, Copenhagen DK-1350, Denmark
³Earth and Planetary Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, Washington, DC 20015, USA⁴Univ. Brest, CNRS, UMR 6539 (Laboratoire des Sciences de l’Environnement Marin), LIA BeBEST, Institut Universitaire Européen de la Mer (IUEM), Place Nicolas Copernic, 29280 Plouzané, France
⁵Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
Copyright Elsevier

Chromium (Cr) isotopes play an important role in cosmochemistry and planetary science, because they are powerful tools for dating (53Mn-53Cr short-lived chronometry), tracing (54Cr nucleosynthetic anomalies) the origins of the materials, and studying the processes involved in volatile element fractionation and planetary differentiation (Cr stable isotopic fractionation). The foundation for using Cr isotopes is to precisely know the compositions of the various chondritic reservoirs. However, the Cr isotope composition of Rumuruti (R) chondrites remains unknown. Here, we report high-precision mass-independent (average 2SE uncertainty of ∼0.02 and ∼0.06 for ε53Cr and ε54Cr, respectively; ε indicates 10,000 deviation) and mass-dependent (uncertainty of average 0.03 ‰ for δ53Cr; δ indicates 1,000 deviation) Cr isotope data for 12 bulk R chondrites of petrologic types 3-6 (included R chondrite breccias), and one R chondrite-like clast (MS-CH) in the Almahata Sitta polymict ureilite. All the R chondrites show homogeneous bulk ε54Cr values, -0.06 ± 0.08 (2SD), similar only to those of the Earth-Moon system and enstatite chondrites. These first ε54Cr data for R chondrites provide significant addition to the ε54Cr-Δ17O diagram, and position them as a potential endmember for planetary precursors. The R chondrites possess a higher 55Mn/52Cr of 0.68 ± 0.04 and higher ε53Cr values 0.23 ± 0.05 (2SD) relative to most of other chondrite groups. This likely results from the lower (e.g. than ordinary and enstatite chondrites) chondrule abundance in R chondrites. The stable Cr isotope composition of R chondrites is homogeneous with a δ53Cr = -0.12 ± 0.03 ‰ (2SD). Combined with previous data of other groups of chondrites, we show that the stable Cr isotopic composition of all the chondrites is homogeneous with δ53Cr of -0.12 ± 0.04 ‰ (2SD, N = 40) and is independent of the petrologic type and redox conditions. The lack of mass-dependent fractionation between all groups of chondrites suggests that the average chondrite δ53Cr value is also representative for the initial composition all differentiated planets in the Solar System. Finally, the MS-CH clast in Almahata Sitta has a Cr isotopic composition (ε53Cr = 0.18 ± 0.04, ε54Cr = -0.16 ± 0.07, and δ53Cr = -0.11 ± 0.05 ‰) that is consistent (within error) with it being an R chondrite-like clast.

¹Yong Xiong,^1,2Ai‐Cheng Zhang,³Noriyuki Kawasaki,⁴Chi Ma,⁵Naoya Sakamoto,¹Jia‐Ni Chen,⁶Li‐Xin Gu,^3,5Hisayoshi Yurimoto
Meteortics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13575]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³Department of Natural History Sciences, Hokkaido University, Sapporo, 060‐0810 Japan
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125 USA
⁵Isotope Imaging Laboratory, Creative Research Institution Sousei, Hokkaido University, Sapporo, 001‐0021 Japan
⁶Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China
Published by Arrangement with John Wiley & Sons

Calcium‐aluminum‐rich inclusions (CAIs) are the first solid materials formed in the solar nebula. Among them, ultrarefractory inclusions are very rare. In this study, we report on the mineralogical features and oxygen isotopic compositions of minerals in a new ultrarefractory inclusion CAI 007 from the CV3 chondrite Northwest Africa (NWA) 3118. The CAI 007 inclusion is porous and has a layered (core–mantle–rim) texture. The core is dominant in area and mainly consists of Y‐rich perovskite and Zr‐rich davisite, with minor refractory metal nuggets, Zr,Sc‐rich oxide minerals (calzirtite and tazheranite), and Fe‐rich spinel. The calzirtite and tazheranite are closely intergrown, probably derived from a precursor phase due to thermal metamorphism on the parent body. The refractory metal nuggets either exhibit thin exsolution lamellae of Fe,Ni‐dominant alloy in Os,Ir‐dominant alloy or are composed of Os,Ir,Ru,Fe‐alloy and Fe,Ni,Ir‐alloy with troilite, scheelite, gypsum, and molybdenite. The later four phases are apparently secondary minerals. The Zr,Sc,Y‐rich core is surrounded by a discontinuous layer of closely intergrown hibonite and spinel. The CAIs are rimmed by Fe‐rich spinel and Al‐rich diopside. Perovskite has high concentrations of the most refractory rare earth elements (REEs) but is relatively depleted in the moderately refractory and volatile REEs, consistent with the ultrarefractory REE pattern. Based on this unusual Zr,Sc,Y‐rich mineral assemblage, the layered distribution in CAI 007, and the REE concentrations in perovskite, we suggest that CAI 007 is an ultrarefractory inclusion of condensation origin. In CAI 007, hibonite, spinel, and probably Al‐rich diopside are 16O‐rich (Δ17O ~–22‰) whereas perovskite and davisite are 16O‐poor (Δ17O ~–3‰). Such oxygen isotope heterogeneity suggests that the UR inclusion formed in the various degrees of 16O‐rich nebular setting or was originally 16O‐rich and then experienced oxygen isotope exchange with 16O‐poor fluid on the CV3 chondrite parent body.

¹Indaram Venugopal,²Thannasi Prabu,³Kasinathan Muthukkumaran,⁴Mylswamy Annadurai
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105116]
¹C&MG LEOS, U R Rao Satellite Centre, Indian Space Research Organization, Bengaluru, 560 017, Karnataka, India
²Dept. of Civil Engineering, National Institute of Technology, Tiruchirappalli, 620015, Tamilnadu, India
³Dept. of Civil Engineering, National Institute of Technology, Tiruchirappalli, 620015, Tamilnadu, India
⁴U R Rao Satellite Centre, Indian Space Research Organization, Bengaluru, 560 017, Karnataka, India

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¹K.Righter,²¹M.Schönbächler,³K.Pando,⁴R.RowlandII,⁵M.Righter,⁵T.Lapene
Earth and Planetary Science Letters 552, 116590 Link to Article [https://doi.org/10.1016/j.epsl.2020.116590]
¹NASA-JSC, 2101 NASA Parkway, Houston, TX 77058, United States of America
²ETH Zürich, Inst. Isotope Geology and Mineral Resources, 8092 Zürich, Switzerland
³Jacobs JETS, NASA JSC, Houston, TX 77058, United States of America
⁴Los Alamos National Laboratory, Mail Stop P952, Los Alamos, NM 87545, United States of America
⁵Dept. of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, United States of America
Copyright Elsevier

The Earth’s timing of accretion and acquisition of moderately volatile compounds is uncertain. Hafnium-W and Mn-Cr isotopic data can bracket the timing of early planetary differentiation and core formation. The Ag-Pd system has also been utilized but its application has been limited by a lack of high pressure and temperature metal-silicate partitioning for Pd and Ag. Because Ag (and Bi) are volatile chalcophile siderophile elements, understanding their early distribution can constrain the origin of volatile elements in differentiated bodies and planets. Unfortunately, neither Ag or Bi have been studied across the wide range of pressure and temperature conditions that are relevant to accretion and core-mantle differentiation. Here, new high-pressure and temperature multi-anvil metal-silicate equilibrium experiments for Bi and Ag have been carried out at conditions relevant to planetary accretion and metal silicate differentiation that allow a more refined and complete understanding of element partitioning during core formation. The new metal-silicate partitioning data are combined with previously reported data, and utilized to predict the distributions of Bi, Pd, and Ag at conditions of accretion relevant for Earth and Mars. Application of the new partitioning results to Earth shows that D(Bi) and D(Ag) (D = metal/silicate concentration ratio) are lowered due to the effect of pressure and Si alloyed in the metallic liquid, resulting in higher predicted mantle Bi and Ag abundances than in the bulk silicate Earth (BSE), as well as high and variable Pd/Ag. The unradiogenic Ag isotopic composition of the BSE could have been generated by early accretion of volatile-poor (high Pd/Ag) pre-cursors, followed by later accretion of volatile–rich (low Pd/Ag) material, in agreement with earlier studies of Pd-Ag and Mn-Cr (Schönbächler et al., 2010). However, these main accretion phases would have to be followed by segregation of a sulfide liquid (at least 1.5% of magma ocean) at high pressures (>30 GPa), to explain the primitive upper mantle (PUM) Bi, Pd, and Ag, as well as Au, Pt, Cu and Ni concentrations as proposed previously. If the early accreted bulk Earth was volatile depleted with high Pd/Ag ratios, portions of the mantle may contain ancient domains that developed positive ¹⁰⁷Ag isotopic anomalies (as also argued by noble gases, Nd, W, and Os isotopes). In comparison, Bi, Pd, and Ag concentrations in the martian mantle could have been set by simple metal-silicate equilibrium. Mars accreted and differentiated relatively rapidly, while also developing a deep magma ocean with a high Pd/Ag ratio that could have evolved positive ¹⁰⁷Ag anomalies, in contrast to Earth. Measurements on shergottites may reveal these predicted Ag isotopic anomalies.