¹M. Yesiltas,²M. Kaya,³T. D. Glotch,⁴R. Brunetto,⁵A. Maturilli,⁵J. Helbert,⁶M. E. Ozel
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13585]
¹Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, 39100 Turkey
²Institute of Acceleration Technologies, Ankara University, Ankara, 06830 Turkey
³Department of Geosciences, Stony Brook University, Stony Brook, New York, 11794 USA
⁴Université Paris‐Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
⁵DLR, Berlin, Germany
⁶Space Sciences and Solar Energy Research and Application Center, Cukurova University, Adana, 01380 Turkey
Published by arrangement with John Wiley & Sons

The Didim meteorite contains multiple lithologies and clasts of different petrologic types in a single stone. A mixture of H5 clasts in an unequilibrated H3 host was previously observed in Didim, according to the initial characterization reported in the Meteoritical Bulletin Database, providing an opportunity to investigate molecular composition that contains varying degree of equilibrium with varying mineralogy. We have taken a “from large scale to small scale” approach to spectroscopically investigate the chemical content of Didim. Centimeter‐scale biconical reflectance spectra show that Didim contains abundant olivine, pyroxene, and other optically active minerals, evident from a strong Band I near 0.93 µm and a weak Band II near 1.75 µm. Micrometer‐scale Raman spectroscopic investigations reveal the presence of carbonaceous material in addition to forsteritic olivine, pyroxene (augite and enstatite), feldspars, and opaque phases such as chromite and hematite. 3‐D Raman tomographic imaging shows that the carbonaceous material near chondrules extends underneath a large olivine grain, going further down toward the interior, indicating that the observed carbonaceous matter is likely indigenous. Nano‐scale infrared measurements reveal that the observed chemical materials in Didim contain spectral, and therefore, molecular, variations at the ~20 nm spatial scale. These chemical variations are normally not accessible via conventional infrared techniques, and indicate the presence of different cations in the molecular composition of observed minerals. By taking the “large scale to small scale” approach, we show that these compositional variations can be captured and investigated nondestructively in meteorites to understand formation/evolution of chemical components in the parent body.

^1,2Yun Jiang,³Piers Koefoed,³Olga Pravdivtseva,^3,4Heng Chen,^2,5Chun‐Hui Li,^2,5Fang Huang,^2,5Li‐Ping Qin,^2,5Jia Liu,³Kun Wang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13588]
¹CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008 China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³Department of Earth and Planetary Sciences, McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, 63130 USA
⁴Lamont‐Doherty Earth Observatory, Columbia University, Palisades, New York, 10964 USA
⁵CAS Key Laboratory of Crust‐Mantle Materials and Environments, School of Earth and Space Sciences,
University of Science and Technology of China, Hefei, Anhui, 230026 China
Published by arrangement with John Wiley & Sons

The alkali element K is moderately volatile and fluid mobile; thus, it can be influenced by both primary processes (evaporation and recondensation) in the solar nebula and secondary processes (thermal and aqueous alteration) in the parent body. Since these primary and secondary processes would induce different isotopic fractionations, K isotopes could become a potential tracer to distinguish them. Using recently developed methods with improved precision (0.05‰, 95% confidence interval), we systematically measured the K isotopic compositions and major/trace elemental compositions of chondritic components (18 chondrules, 3 CAIs, 2 matrices, and 5 bulks) in the carbonaceous chondrite fall Allende. Among all the components analyzed in this study, CAIs, which formed initially under high‐temperature conditions in the solar nebula and were dominated by nominally K‐free refractory minerals, have the highest K2O content (average 0.53 wt%) and have K isotope compositions most enriched in heavy isotopes (δ41K: −0.30 to −0.25‰). Such an observation is consistent with previous petrologic studies that show CAIs in Allende have undergone alkali enrichment during metasomatism. In contrast, chondrules contain lower K2O content (0.003–0.17 wt%) and generally lighter K isotope compositions (δ41K: −0.87‰ to −0.24‰). The matrix and bulks are nearly identical in K2O content and K isotope compositions (0.02–0.05 wt%; δ41K: −0.62 to − 0.46‰), which are, as expected, right in the middle of CAIs and chondrules. This strongly indicates that most of the chondritic components of Allende suffered aqueous alteration and their K isotopic compositions are the ramification of Allende parent‐body processing instead of primary nebular signatures. Nevertheless, we propose the small K isotope fractionations observed (< 1‰) among Allende components are likely similar to the overall range of K isotopic fractionation that occurred in nebular environment. Furthermore, the K isotope compositions seen in the components of Allende in this study are consistent with MC‐ICP‐MS analyses of the components in ordinary chondrites, which also show an absence of large (10‰) isotope fractionations. This is not expected as evaporation experiments in nebular conditions suggest there should be large K isotopic fractionations. Nevertheless, possible nebular processes such as chondrules back exchanging with ambient gas when they formed could explain this lack of large K isotopic variation.

^1,2Shuya Tan,^1,3Yasuhito Sekine,⁴Takazo Shibuya,²Chihiro Miyamoto,²Yoshio Takahashi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114222]
¹Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Tokyo, Japan
²Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan
³Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan
⁴Super-cutting-edge Grand and Advanced Research (SUGAR) Program, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
Copyright Elsevier

There are several lines of evidence for the subsurface ocean within Europa; however, its oceanic chemistry and geochemical cycles are largely unknown. The recent observations by large telescopes show that exogenic sulfur ions and SO₂ are implanted from Io and accumulate as sulfuric acids in Europa’s trailing hemisphere. This suggests that a large amount of sulfate could have been supplied into the ocean over geological timescales. The telescope observations also suggest that chloride salts appear on chaotic terrains of Europa, suggesting that the primary oceanic anion may be chloride despite a supply of sulfate into the ocean. These observations imply the presence of possible sinks of exogenic sulfate within the ocean. Here, we report the results of laboratory experiments on hydrothermal sulfate reduction under the pressure conditions that correspond to Europa’s seafloor. Using a Dickson-type experimental system, we obtain the reaction rate of sulfate reduction at a pressure of 100 MPa and temperature of 280 °C for various pH levels (pH 2–7). We find strong pH dependence and little pressure dependence of the reaction rate. Sulfate reduction proceeds effectively at fluid pH < 6, whereas it is kinetically inhibited at fluid pH ~7. These results suggest that, if hydrothermal fluid pH is <6, hydrothermal sulfate reduction within Europa can be a sink of exogenic sulfate within the ocean in addition to precipitation of sulfate salts. Such acidic fluid pH may be achieved if hydrothermal activity is hosted by basaltic rocks. We suggest the importance of the thermal evolution of the rocky interior for both the ocean chemistry and sulfur cycles of Europa.

^1,2Xunyu Zhang,³Minggang Xie,^4,1,2,5Zhiyong Xiao
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114214]
¹State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, PR China
²CNSA Macau Center for Space Exploration and Science, Macau, PR China
³College of Science, Guilin University of Technology, Guilin 541006, PR China
⁴School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, PR China
⁵CAS Center for Excellence in Comparative Planetology, Hefei 230026, PR China
Copyright Elsevier

The South Pole-Aitken (SPA) basin is the largest impact structure on the Moon and is believed to have excavated the orthopyroxene (Opx)-rich lower crust and/or upper mantle materials. For the complex craters outside of the SPA transient cavity, the origin of the Opx-rich central peaks is possibly from either the Opx-rich materials of the SPA ejecta deposits or the unexcavated lower crust and/or upper mantle. To estimate the thickness of the Opx-rich materials of the SPA ejecta deposits, this study investigated large complex craters (dozens of kilometers) that have penetrated the Opx-rich materials and exposed deeper mafic-poor crustal material based on spectra extracted from small fresh craters (sub-kilometer scale). The amount of foreign material introduced to these large complex craters by other lunar impact events was estimated to guarantee the least influence on the compositional analysis. The study results suggest that a 56 km-diameter crater at ~640 km northwest of the SPA center is large enough to penetrate the Opx-rich materials of the SPA ejecta deposits, which are thinner than ~4.7 km at this location. This result also indicates that the intense bombardment history of the large craters and basins outside of the SPA transient cavity excavated and redistributed a large amount of crustal material across the basin, possibly resulting in the heterogeneous distribution of mafic-rich and mafic-poor materials on the SPA surface.

^1,2Pauliš, P.,³Černý, D.,⁴Malý, T.,²Dolníček, Z.,⁵Bohatý, M.,²Ulmanová, J.,⁶Pour, O.,⁷Plášil, J.,⁸Malina, O.,⁶Bohdálek, P.,⁹Sýkora, I.,⁹Povinec, P.P.
Bulletin Mineralogie Petrologie 28, 179-202 Link to Article [DOI: 10.46861/bmp.28.179]
¹Smíškova 564, Kutná Hora, 284 01, Czech Republic
²Mineralogicko-petrologické oddělení, Národní muzeum, Cirkusová 1740, Praha 9-Horní Počernice, 193 00, Czech Republic
³Merklín 23, Merklín, 362 34, Czech Republic
⁴Matouškova 265, Rovensko pod Troskami, 512 63, Czech Republic
⁵Radnická 7, Brno, 602 00, Czech Republic
⁶Česká geologická služba, Geologická 6, Praha 5, 152 00, Czech Republic
⁷Fyzikální ústav AV ČR v.v.i., Na Slovance 2, Praha 8, 182 21, Czech Republic
⁸Národní památkový ústav, územní odborné pracoviště v Lokti, Kostelní 81/25, Loket, 357 33, Czech Republic
⁹Katedra jadrovej fyziky a biofyziky, Fakulta matematiky, fyziky a informatiky, Univerzita Komenského, Bratislava, 842 48, Slovakia

¹Evatt, G.W.,¹Smedley, A.R.D.,²Joy, K.H.,¹Hunter, L.,³Tey, W.H.,^1,4Abrahams, I.D.,⁵Gerrish, L.
Geology 48, 683-687 Link to Article [DOI: 10.1130/G46733.1]
¹Department of Mathematics, University of Manchester, Manchester, M13 9PL, United Kingdom
²Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, United Kingdom
³Department of Mathematics, Imperial College London, London, SW7 2AZ, United Kingdom
⁴Isaac Newton Institute for Mathematical Sciences, University of Cambridge, Cambridge, CB3 0EH, United Kingdom
⁵British Antarctic Survey, Cambridge, CB3 0ET, United Kingdom

¹Maria M. Costa et al. (>10)
Proceeedings of the National Academy of Sciences of the Unted States of America (in Press) Link to Article [DOI:
https://doi.org/10.1073/pnas.2016326117]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, 1350 Copenhagen, Denmark

Combining U–Pb ages with Lu–Hf data in zircon provides insights into the magmatic history of rocky planets. The Northwest Africa (NWA) 7034/7533 meteorites are samples of the southern highlands of Mars containing zircon with ages as old as 4476.3 ± 0.9 Ma, interpreted to reflect reworking of the primordial Martian crust by impacts. We extracted a statistically significant zircon population (n = 57) from NWA 7533 that defines a temporal record spanning 4.2 Gyr. Ancient zircons record ages from 4485.5 ± 2.2 Ma to 4331.0 ± 1.4 Ma, defining a bimodal distribution with groupings at 4474 ± 10 Ma and 4442 ± 17 Ma. We interpret these to represent intense bombardment episodes at the planet’s surface, possibly triggered by the early migration of gas giant planets. The unradiogenic initial Hf-isotope composition of these zircons establishes that Mars’s igneous activity prior to ∼4.3 Ga was limited to impact-related reworking of a chemically enriched, primordial crust. A group of younger detrital zircons record ages from 1548.0 ± 8.8 Ma to 299.5 ± 0.6 Ma. The only plausible sources for these grains are the temporally associated Elysium and Tharsis volcanic provinces that are the expressions of deep-seated mantle plumes. The chondritic-like Hf-isotope compositions of these zircons require the existence of a primitive and convecting mantle reservoir, indicating that Mars has been in a stagnant-lid tectonic regime for most of its history. Our results imply that zircon is ubiquitous on the Martian surface, providing a faithful record of the planet’s magmatic history.

¹G.Alemanno,²E.Garcia-Caurel,¹J.Carter,¹F.Poulet, ¹R.Brunetto,¹A.Alèon-Toppan,¹R.G.Urso, ¹O.Mivumbi,³C.Boukari,³V.Godard,⁴F.Borondics
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105138]
¹Universitè Paris-Saclay, CNRS, Institut d’astrophysique spatiale, 91405, Orsay, France
²LPICM, CNRS, Ecole Polytechnique, IPParis, 91128, Palaiseau, France
³CNRS GEOPS UMR 8148 Bassin et Ressources, Bâtiment 504, Orsay, Cedex, France
⁴Synchrotron Soleil, L’Orme des Merisiers, Saint-Aubin–BP48, 91192, Gif-sur-Yvette, CEDEX, France

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Ed Cloutis,¹ Daniel Applin,¹ Stephanie Connell,¹Krista Kubanek,¹Jesse Kuik,¹Alexis Parkinson,¹Mary Ramirez,¹Nathalie Turenne,²Stanley Mertzman
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105130]
¹Department of Geography, 515 Portage Avenue, University of Winnipeg, Winnipeg, MB, R3B 2E9, Canada
²Department of Earth and Environment, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA, 17604 3003, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹AlexanderSehlke,¹Derek W.G.Sears,²Scott S.Hughes
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.105129]
¹Bay Area Environmental Research Institute, NASA Ames Research Center, Mountain View, California 95035, USA
²Geosciences Department, Idaho State University, Pocatello, Idaho 83209, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here