¹Chelsea D.Willett,¹William S.Cassata,¹Naomi E.Marks
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.04.017]
¹Nuclear and Chemical Science Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA
Copyright Elsevier

Novel analytical approaches to determining the trapped 38Ar/36Ar ratio of gases contained within Martian meteorites are presented and applied to the Martian regolith breccia Northwest Africa (NWA) 7034 and paired stone NWA 11220. The resulting data indicate that extensive mass-dependent fractionation of atmospheric Ar may have occurred within 150 million years of planetary formation, ostensibly as a result of diffusion-limited hydrodynamic escape. The inferred fractional loss of Ar and lighter atmospheric constituents exceeds 50%. These data suggest that volatiles derived from planetary outgassing and/or impactors may dominate the present abundance of atmospheric Ar.

¹Tamara E. Koch,¹Dominik Spahr,¹Beverley J. Tkalcec,²Oliver Christ,¹Philomena-Theresa Genzel,¹Miles Lindner,¹David Merges,³Fabian Wilde,¹Björn Winkler,^1,4Frank E. Brenker
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13815]
¹Institute of Geosciences, Goethe University Frankfurt, Altenhoeferallee 1, 60438 Frankfurt am Main, Germany
²Department of Geoscience, University of Padua, Via Gradenigo 6, 35131 Padua, Italy
³Helmholtz-Zentrum Hereon, Max-Planck Strasse 1, 21502 Geesthacht, Germany
⁴Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, 1680 East-West Road, Honolulu, Hawaii, 96822 USA
Published arrangement with John Wiley & Sons

In order to gain further insights into early solar system aggregation processes, we carried out an experiment on board the International Space Station, which allowed us to study the behavior of dust particles exposed to electric arc discharges under long-term microgravity. The experiment led to the formation of robust, elongated, fluffy aggregates, which were studied by scanning electron microscopy, electron backscatter diffraction, and synchrotron micro-computed tomography. The morphologies of these aggregates strongly resemble the typical shapes of fractal fluffy-type calcium-aluminum-rich inclusions (CAIs). We conclude that a small amount of melting could have supplied the required stability for such fractal structures to have survived transportation and aggregation to and compaction within planetesimals. Other aggregates produced in our experiment have a massy morphology and contain relict grains, likely resulting from the collision of grains with different degrees of melting, also observed in some natural CAIs. Some particles are surrounded by igneous rims, which remind in thickness and crystal orientation of Wark–Lovering rims; another aggregate shows similarities to disk-shaped CAIs. These results imply that a (flash-)heating event with subsequent aggregation could have been involved in the formation of different morphological CAI characteristics.

¹Svetlana N. Teplyakova,¹Cyril A. Lorenz,¹Marina A. Ivanova,²Munir Humayun,¹Nataliya N. Kononkova,³Sergey E. Borisovsky,¹Alexander V. Korochantsev,⁴Ian A. Franchi,⁵Nina G. Zinovieva
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13814]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, 119991 Russia
²National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida, 32310 USA
³Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry RAS, Staromonetnyi per, 35, Moscow, 119017 Russia
⁴Planetary and Space Sciences Research Institute, Open University, Milton Keynes, MK7 6AA UK
⁵Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991 Russia
Published by arrangement with John Wiley & Sons

Karavannoe is a pallasite found in Russia in 2010. The mineralogy, chemistry, and oxygen isotopic composition indicate that Karavannoe is a member of the Eagle Station Pallasite (ESP) group. Karavannoe contains mostly olivine and subdued interstitial Fe,Ni-metal. Zoned distribution of FeO in small, rounded grains of olivine and FeO and Al2O3 in chromite shows that the cooling rate of the melt was fast during the crystallization of the round olivine grains. Siderophile element distribution and correlations of Au-As and Os-Ir concentrations in Karavannoe and the other ESP metal record its magmatic origin. FeO-rich composition of olivine, low W and Ga, and high Ni abundances in the Karavannoe metal indicate the formation of the metal from an oxidized chondrite precursor. Model calculations demonstrate that the ESPs’ metal compositions correspond to the solids of the fractional crystallization of CV- or CO-chondrite-derived metallic liquids. The Karavannoe metal composition corresponds to the solid fraction crystallized after ~40% fractional crystallization. The Mg/(Mg+Fe) atom ratio of complementary silicate liquid corresponds to Fo70, possibly indicating that the olivine is not in equilibrium with the metal and could have been a product of the late evolutionary processes in the Karavannoe parent body mantle. In any ESP genesis Karavannoe was not in equilibrium with its metal and is a product of mantle differentiation processes. Olivine of Karavannoe and ESPs is similar in composition, while the metal is different. We propose a model of ESP formation involving an impact-induced intrusion of liquid core metal into a basal mantle layer, followed by fractional crystallization of the metal. The metal textures and chemical zoning of Karavannoe minerals point to remelting and rapid cooling due to a later impact event.

¹Yang He,¹Xiao-Wen Liu,¹Ai-Cheng Zhang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13817]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 China
Published by arrangemnt with John Wiley & Sons

In this study, we report the petrography and mineralogy of a brecciated eucrite Northwest Africa (NWA) 8021, which shows a locally layered texture with one layer containing graphic clasts and Si,Ti-rich regions. The graphic clasts contain rod-like grains of silica phases, augite, K-feldspar, and Ca-phosphate minerals included in anorthite. Some of the clasts contain relatively coarse grains of quartz, K-feldspar, and augite, which are chemically different from the rod-like phases, indicating different origins. All of the augite grains in the graphic clasts have rare earth element (REE) concentrations higher than those in typical eucrites. The bulk Na2O+K2O contents of the graphic clasts are higher than typical eucrites. All of these chemical features indicate that the graphic clasts were probably derived from an evolved parent rock. Low-degree partial melting of the eucritic crust (<10%) is required to generate a melt equilibrated with the REE-rich rod-like pyroxene from the graphic clasts. The Si,Ti-rich regions contain high abundances of silica phases (~52 vol%) and ilmenite (~9 vol%), probably derived from an evolved Si,Ti-rich rock (dacite). The evolved components observed in NWA 8021 are different from other evolved components observed in howardites and indicate more diverse evolution in the eucrite parent body than previously thought.

¹Miranda C. Holt,¹Christopher D. K. Herd
Meteoritics & Planetary Science (in Press) Link tp Article [https://doi.org/10.1111/maps.13819]
¹Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3 Canada
Published by arrangement with John Wiley & Sons

This study examined nine pristine samples representing seven lithologies of the ungrouped C2 carbonaceous chondrite Tagish Lake from the University of Alberta Meteorite Collection using scanning electron microscope and electron probe microanalyzer analyses to characterize the sulfide mineralogy, textures, and compositions present. Four distinct sulfide morphologies were identified including pyrrhotite containing exsolved pentlandite, unexsolved pyrrhotite, and unexsolved pentlandite, and a unique “bull’s-eye” sulfide morphology. The at% Fe/Ni of the pyrrhotite grains within these samples decreases with increasing degree of alteration and roughly places them in the alteration order of TL11v chip1 < TL4 < TL11v chip2 < TL5b ≤ TL10a < TL 11h < TL1 < TL11i. The at% Fe/Ni of low Ni (<1 wt% Ni) pyrrhotite indicates that the overall degree of alteration of Tagish Lake lies between that of CM1/2 and CI chondrites. Comparison of the composition of the sulfides to established Fe-Ni-S phase diagrams at different temperatures indicates two separate generations of sulfide formation. They are (1) high-temperature formation of exsolved pyrrhotite–pentlandite and much of the unexsolved pentlandite at ~500–600 °C, likely by cooling of a monosulfide solid solution melt during chondrule formation; and (2) low-temperature formation of unexsolved pyrrhotite, some unexsolved pentlandite, pyrrhotite containing flame-like pentlandite bodies, and bull’s-eye sulfides at ~25–100 °C, likely formed during aqueous alteration events on the Tagish Lake parent body.

¹J. M. Young,¹T. D. Glotch,²M. Yesiltas,³V. E. Hamilton,⁴L. B. Breitenfeld,⁵H. A. Bechtel,⁵S. N. Gilbert Corder,⁵Z. Yao
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007166]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
²Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, Turkey
³Southwest Research Institute, Boulder, CO, USA
⁴Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
⁵Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
Published by arrangement with John Wiley & Sons

Mid-infrared (MIR) spectroscopy has been used with great success to quantitatively determine the mineralogy of geologic samples. It has been employed in a variety of contexts from determining bulk composition of powdered samples to spectroscopic imaging of rock thin sections via micro-FTIR. Recent advances allow for IR measurements at the nanoscale. Near field nanoscale infrared imaging and spectroscopy with a broadband source (nano-FTIR) enable understanding of the spatial relationships between compositionally distinct materials within a sample. This will be of particular use when analyzing returned samples from Bennu and Ryugu, which are thought to be compositionally like CI or CM2 carbonaceous chondrites. Returned samples will likely contain olivine/pyroxene chondrules that have been transformed into hydrous phyllosilicates, sulfides, carbonates, and other alteration phases. The use of near-field infrared techniques to probe the boundaries between once pristine chondrules and alteration phases at the nanoscale is a novel approach to furthering our understanding of the compositional evolution of carbonaceous asteroids and the processes that drive their evolution. Here we report the results of nano-FTIR spectroscopy and imaging measurements performed on the carbonaceous chondrite Allan Hills (ALH) 83100 (CM1/2). We show with nanoscale resolution that spatially resolved Fe-Mg variations exist within the phylosilicates around a chondrule rim. We also present effects of crystal orientation on the nano-FTIR spectra to account for the spectral differences between the meteorite and mineral spectra.

¹S. Griffin,^1,2,3,4L. Daly,⁵S. Piazolo,²L. V. Forman,⁶B. E. Cohen,¹M. R. Lee,⁷P. W. Trimby,^8,9R. J. Baumgartner,^2,10,11G. K. Benedix,¹B. Hoefnagels
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007082]
¹School of Geographical and Earth Sciences, University of Glasgow, UK
²School of Earth and Planetary Sciences, Space Science and Technology Centre, Curtin University, Australia
³Australian Centre for Microscopy and Microanalysis, The University of Sydney, Australia
⁴Department of Materials, University of Oxford, UK
⁵School of Earth and Environment, University of Leeds, UK
⁶Department of Materials, University of Oxford, UK. 5School of Geosciences, University of Edinburgh, UK
⁷Oxford Instruments Nano analysis, High Wycombe, UK
⁸School of Biological, Earth and Environmental Sciences, The University of New South Wales, Kensington, NSW, Australia
⁹CSIRO Mineral Resources, Australian Resources Research Centre, Kensington, WA, Australia
¹⁰Department of Earth and Planetary Sciences, Western Australia Museum, Australia
¹¹Planetary Institute, USA
Published by arrangment with John Wiley & Sons

Deformation is a near ubiquitous process that is observed within nearly all naturally forming rocks. Electron backscatter diffraction (EBSD) is a technique that enables slip-systems (a form of plastic deformation) to be inferred from intra-crystalline misorientations at a comparable scale to representative CPO analysis (≥300 crystals for the nakhlites). Extensive laboratory and studies on naturally occurring samples have identified preferential mantle condition extrinsic parameters for specific slip-system signatures within olivine and clinopyroxene. Intra-crystalline misorientation patterns for olivine and augite (high Ca-clinopyroxene) for 16 different Martian nakhlite meteorites (21 sections) were analysed and assessed against these known parameters. Investigation of high and low deformation regions within the nakhlites revealed a shift in intra-crystalline misorientation patterns for 10 of the 21 sections. Interpreted as both shock (high deformations) and emplacement (low deformation) signatures. The observed variations in deformation patterns for the two main regimes of deformation indicate heterogeneous sampling of the nakhlite ejecta crater. Our findings indicate that shock deformation is prevalent throughout the nakhlites, and that great care needs to be taken when interpreting intra-crystalline misorientations of crystals within apparent lower deformation regions.

¹L. He,²R. E. Arvidson,²J. A. O’Sullivan,³R. V. Morris,²T. Condus,²M. N. Hughes,⁴K. E. Powell
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007092]
¹Department of Electrical and Systems Engineering, Washington University in St. Louis, MO
²Department of Earth and Planetary Science, Washington University in St. Louis, MO
³NASA/Johnson Space Center, Houston, TX
⁴School of Earth and Space Exploration, Arizona State University, AZ
Published by arrangement with John Wiley & Sons

The Mars Reconnaissance Orbiter Compact Imaging Spectrometer for Mars (CRISM) covers the spectral range from 0.362 to 3.92 µm with a midafternoon local solar time data acquisition. For equatorial to midlatitudes, depending on the season and surface materials, wavelengths longer than ∼2.65 µm exhibit spectral radiances on sensor that include sunlight and thermal-emission related terms. We developed a radiative transfer based neural network approach to model both solar and emitted terms in which surface kinetic temperatures are retrieved for each image pixel, together with single scattering albedo (SSA) spectra, over the full CRISM wavelength range. We applied the method to along-track oversampled scene FRT00021C92 over Glen Torridon within Gale Crater, where the Curiosity rover traversed and acquired remote sensing and in-situ data. Synergistic analysis of orbital and rover-based data, coupled with laboratory analyses of ferric-rich smectites, provide a self-consistent set of results for the presence of desiccated nontronite associated with Murray formation mudstones exposed as periodic bedrock ridges located just to the south of Vera Rubin ridge. The desiccated nature is consistent with Curiosity’s CheMin data, which for Glen Torridon drill samples indicate an abundance of nontronite having a collapsed structure resulting from loss of interlayer H2O.

¹Yang He,¹Xiao-Wen Liu,¹Ai-Cheng Zhang
Meteoritics & Planetary Science (in Press) Kink to Article [https://doi.org/10.1111/maps.13817]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 China
Published by arrangement with John Wiley & Sons

In this study, we report the petrography and mineralogy of a brecciated eucrite Northwest Africa (NWA) 8021, which shows a locally layered texture with one layer containing graphic clasts and Si,Ti-rich regions. The graphic clasts contain rod-like grains of silica phases, augite, K-feldspar, and Ca-phosphate minerals included in anorthite. Some of the clasts contain relatively coarse grains of quartz, K-feldspar, and augite, which are chemically different from the rod-like phases, indicating different origins. All of the augite grains in the graphic clasts have rare earth element (REE) concentrations higher than those in typical eucrites. The bulk Na2O+K2O contents of the graphic clasts are higher than typical eucrites. All of these chemical features indicate that the graphic clasts were probably derived from an evolved parent rock. Low-degree partial melting of the eucritic crust (<10%) is required to generate a melt equilibrated with the REE-rich rod-like pyroxene from the graphic clasts. The Si,Ti-rich regions contain high abundances of silica phases (~52 vol%) and ilmenite (~9 vol%), probably derived from an evolved Si,Ti-rich rock (dacite). The evolved components observed in NWA 8021 are different from other evolved components observed in howardites and indicate more diverse evolution in the eucrite parent body than previously thought.

^1,2Joshua F.Snape,³Alexander A.Nemchin,³Tim Johnson,¹Stefanie Luginbühl,⁴Jasper Berndt,⁴Stephan Klemme,⁵Laura J.Morrissey,¹Wim van Westrenen
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.04.008]
¹Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
²Department of Earth and Environmental Sciences, The University of Manchester, Manchester, M13 9PL, UK
³School of Earth and Planetary Sciences, The Institute of Geoscience Research, Curtin University, Perth, WA 6845, Australia
⁴Institute of Mineralogy, University of Münster, Germany
⁵Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
Copyright Elsevier

This study presents the results of high pressure and temperature experiments to investigate the mineral–melt trace element partitioning behaviour for minerals predicted to have formed during the crystallisation of the Lunar Magma Ocean (LMO). The focus of this work has been particularly on determining partition coefficients for parent–daughter pairs of radiogenic elements, for LMO-relevant temperatures, pressures and compositions. The new experimental data are compared with previous studies for the same minerals and elements in order to establish best estimates for the partition coefficient of each element for evolving compositions of minerals as predicted in recent studies modelling LMO crystallisation. These estimates are used to calculate evolving parent–daughter ratios in the LMO residual melt and crystallising minerals for the four main long-lived radiogenic isotope systems that have been studied in lunar samples (Rb–Sr, Sm–Nd, Lu–Hf and U–Pb). The calculated 87Rb/86Sr, 147Sm/144Nd, and 176Lu/177Hf ratios are consistent with predictions for the mantle sources of lunar basalts and evolved lithologies. In contrast, it is difficult to explain the wide range of 238U/204Pb source ratios predicted from the Pb isotopic compositions of basaltic lunar samples. Potential explanations for this observation are discussed, with the conclusion that the Moon most likely experienced a significant loss of volatiles (including Pb), towards the end of LMO crystallisation, resulting in the dramatic U–Pb fractionation evidenced by recent sample analyses.