^1,2M.Konstantinidis,¹E.A.Lalla,¹M.G.Daly,³G.Lopez-Reyes,^4,5J.M.Stromberg,⁶K.Cote,⁵E.A.Cloutis
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114113]
¹Centre for Research in Earth and Space Science, York University, 4700 Keele St., Toronto M3J 1P3, Canada
²Department of Mathematics and Statistics, York University, 4700 Keele St., Toronto M3J 1P3, Canada
³Unidad Asociada Universidad de Valladolid-CSIC-CAB, C/Francisco Valles 8, 47151 Boecillo, Valladolid, Spain
⁴CSIRO Mineral Resources, 26 Dick Perry Ave, Kensington, WA 6151, Australia
⁵Department of Geography, University of Winnipeg, 515 Portage Ave, Winnipeg, Manitoba R3B 2E9, Canada
⁶Department of Physics, University of Toronto, 60 St George St, Toronto, ON M5S 1A7, Canada
Copyright Elsevier

As space agencies plan for the continuous deployment of rovers and landers to planetary bodies such as the Moon and Mars, an in-depth, quantitative, and qualitative understanding of the observations is essential. One objective of planetary exploration focuses on planetary geochemistry and biochemistry with an emphasis on the search for possible biosignatures and related minerals. To this end, we present the elemental quantification of samples from the CanMars analogue sample return mission conducted in Hanksville, UT, USA. Measurements were carried out in a laboratory at York University, Canada, using the Laser-induced Breakdown Spectroscopy Raman Sensor (LiRS) instrument- a breadboard for future space concept. A linear Mixture Model (LMM) was used to quantify the abundance of major elements of 10 samples from the resulting Laser-induced Breakdown Spectroscopy LIBS spectra with a calibration set based on the sample mineralogy. We assess the quantification achieved by LiRS and the LMM by error analysis, which resulted in root mean squared error, absolute error, and percentage relative error of less than 1.299 %  ± 0.114% (wt%), 0.959 ± 0.010 (wt%), and 9.613 %  ± 1.914% (of wt%), respectively. The results in question suggest that by complementing information obtained from various sources such as Raman spectroscopy, X-ray diffraction, and Reflectance spectroscopy, the quantification of LIBS may be significantly improved, from which subsequent geochemical inferences may be made. Within the scope of the CanMars analogue mission, these results show an advancement over past results with possible implications for ongoing and future sample return missions such as the OSIRIS-REx and the Mars2020 Perseverance Rover.

¹W.H.Farrand,²J.W.Rice,²F.C.Chuang,³A.D.Rogers
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114111]
¹Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
²Planetary Science Institute, 1700 East Ft. Lowell, Suite 106, Tucson, AZ 85719, USA
³Stony Brook University, Department of Geoscience, 255 ESS Building, Stony Brook, NY 11794, USA
Copyright Elsevier

Small-scale domes with circumferential aprons and concentric aureoles in western Arcadia Planitia (34–41°N, 167–179°E) near Tyndall crater were examined using a suite of datasets including CRISM, THEMIS IR, HiRISE, and CTX. Previous studies based primarily on photogeologic evidence suggested that these domes were analogous to terrestrial felsic cryptodomes to extrusive lava domes. The domes have also been examined using CRISM visible/near infrared to short-wave infrared (VNIR-SWIR) reflectance spectra which indicated the presence of ferrous silicate minerals in association with the domes. This study presents further CRISM spectral evidence for 1) high-Ca pyroxene and glass mixtures with, or possibly without, the presence of olivine on the flanks of some domes, 2) 1.3 μm band absorption features consistent with an Fe-bearing plagioclase or possibly a Fe-rich alkali feldspar in more limited occurrences at the base of some domes, 3) spectral convexity between 3.4 and 3.9 μm associated with rocky, light-toned portions on top of some domes which is attributed to the presence of alkali-rich plagioclase or alkali feldspars. New morphologic observations include a possible cinder cone and arcs of light-toned, “brain terrain” material on the pole-facing upper margins of some aprons which, in combination with ice-associated “brain terrain” on light-toned outer aureoles suggests an association with ice. The morphology of an assortment of domes and association with alkali feldspars suggests they represent a continuum from intrusive cryptodomes to flat extrusive domes, potentially of felsic composition although formation from viscous alkali-rich mafic magmas is not precluded.

¹Huimin Shao,¹Hiroshi Isobe,²Bingkui Miao
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13563]
¹Department of Earth and Environmental Sciences, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 8608555 Japan
²Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, 541004 China
Published by arrangement with John Wiley & Sons

The chemical composition and texture of cosmic spherules are influenced by atmospheric conditions and the characteristics of their parent interplanetary particles. The objective of this study was to reproduce I‐type cosmic spherules, which consist mainly of Fe oxide and Fe‐Ni metal, and compare their textural characteristics with those of natural I‐type cosmic spherules. Thus, a series of rapid heating and quenching experiments were performed on free falling iron meteorite powders obtained from Canyon Diablo, in the United States. The experiments were conducted using a high‐temperature furnace with controlled gas flow rates at oxygen fugacities of FMQ + 2.4, FMQ, and FMQ − 2.5 log unit. The resulting Fe‐Ni metal and oxide phases showed the nonequilibrium state of the melted spherules formed during quenching. Two types of magnetite crystals in different orientations were found in iron oxide. As temperatures decreased, the molten metal was oxidized to form immiscible molten iron oxide that then covered the former. As the oxide melt increased at the expense of metal, magnetite began to crystallize from the iron oxide melt, as the liquidus phase, either on the surface or within the melt phase. The characteristics of the run products obtained under different oxygen fugacities were similar to those of natural I‐type cosmic spherules, which have textures and compositions that may contain information regarding the oxygen content of the upper atmosphere. Our study suggests that CO2‐bearing molecules in the atmosphere could form iron oxide with a texture similar to natural I‐type cosmic spherules. During this process, rapid crystallization of magnetite plays an important role in texture formation in disequilibrium states.

¹Andreas Morlok,¹Iris Weber,¹Aleksandra N. Stojic,²Martin Sohn,¹Addi Bischoff,³Dayl Martin,¹Harald Hiesinger,⁴Joern Helbert
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13568]
¹Institut für Planetologie, Westfälische Wilhelms Universität, Münster, Wilhelm‐Klemm‐Str. 10, Münster, 48149 Germany
²Hochschule Emden/Leer, Constantiaplatz 4, Emden, 26723 Germany
³European Space Agency, Fermi Avenue, Harwell Campus, Didcot, Oxfordshire, OX11 0FD UK
⁴Institute for Planetary Research, DLR, Rutherfordstrasse 2, Berlin, 12489 Germany
Published by arrangement with John Wiley & Sons

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).

¹Tatiana Mijajlovic,¹Xi Xue,¹Erin Walton
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13569]
¹Department of Physical Sciences, MacEwan University, 10700 104 Ave, Edmonton, Alberta, T5J 2S2 Canada
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 032 is an unbrecciated porphyritic basalt found in the Moroccan desert in 1999. Constituent igneous minerals—olivine, pyroxene, and plagioclase—exhibit shock deformation and transformation effects. NWA 032 is among the youngest radiometrically dated sample from the Moon, with concordant Sm‐Nd and Rb‐Sr ages of 2.947 ± 0.016 Ga and 2.931 ± 0.092, respectively, representing the timing of igneous crystallization. We present the first comprehensive study of shock metamorphism in NWA 032, with a focus on the structural state of fine‐grained plagioclase feldspar, shock deformation in olivine and pyroxene, and the microtexture and mineralogy of shock melts. Micro‐Raman spectroscopy, optical properties, and electron imaging confirm that plagioclase in this meteorite has been shock amorphized, which, for calcic plagioclase (An80‐90), requires shock pressures on the order of ~25–27 GPa. Shock pressures in this range are accompanied by a postshock temperature increase <200 °C. Shock deformation in olivine and pyroxene phenocrysts comprises undulose extinction to weak mosaicism, irregular fractures, polysynthetic mechanical twinning in pyroxene, and development of planar fractures in olivine. The shock effects in mafic minerals constrain the upper limit of shock in NWA 032 to have been <30 GPa. Shock melt in NWA 032 has quenched to glass of basaltic composition, representing localized in situ melting of igneous minerals by shearing along lithological boundaries to form shock veins and shock impedance contrasts to form isolated pockets of shock melt. These melts quench‐crystallized olivine and pyroxene during the pressure release (<14 GPa). Using recent experimental data on shock amorphization of feldspars, coupled with constraints on the formation of metastable minerals associated with shock melt, we have revised the shock pressure experienced by paired meteorites NWA 10597, NWA 4734, and LaPaz Icefield 02205/02224/0226/02436/03632/04841. These largely unbrecciated, basaltic meteorites experienced an equilibration shock pressure on the order of ~22–25 GPa, constrained by partial amorphization of precursor igneous bytownite. Our results are consistent with crater pairing and ejection in a single impact cratering event.

^1,2Alexandra N. Rupert,^1,2Phil J.A. McCausland,^1,2Roberta L. Flemming
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13572]
¹Department of Earth Sciences, Western University, London, Ontario, N6A 5B7 Canada
²Institute for Earth and Space Exploration, Western University, London, Ontario, N6A 5B7 Canada
Published by arrangement with John Wiley & Sons

Ordinary chondrites record shock metamorphism resulting from hypervelocity collisions on small bodies, and underpin the petrographic assessment of shock stage, a scale of progressive stages of shock metamorphism from S1 (unshocked) to S7 (shock melted). In this work, olivine grains in 11 L and LL chondrites (S1–S5) were investigated in thin section and hand sample using in situ two‐dimensional X‐ray diffraction (2‐D XRD). Olivine grains were measured under a 300 µm X‐ray beam for multiple lattice reflections, by measuring diffracted streak length along the chi (χ) dimension (Debye ring dimension), to examine their strain‐related mosaicity. Olivine strain‐related mosaicity was observed to increase with greater shock deformation, with more complex multi‐peak streaks apparent at higher shock levels. The full width at half maximum (FWHMχ) of the simple peak shapes along χ was measured to quantify petrographic shock stage for comparison with that described optically. The average FWHMχ values for simple peaks in olivine show an increase with increasing shock stage: S1 (0.44°± 0.06°), S2 (0.58°± 0.11°), S3 (0.67°± 0.15°), S4 (0.76°± 0.13°), and S5 (0.86°± 0.12°). This method complements optical petrographic methods and offers a ±1 shock stage accuracy in determining shock stage. In particular, 2‐D XRD analysis of strain‐related mosaicity allows quantitative analysis of shock stage in shock‐darkened samples that are difficult to work with petrographically, and for hand samples without need for thin section preparation.

^1,2,3,4Gerasimov, S.I.,¹Malyarov, D.V.,²Sirotkina, A.G.,¹Kapinos, S.A.,^1,4Kalmykov, A.P.,¹Knyazev, A.S.
Combustion, Explosion and Shock Waves 56, 486-493 Link to Article [DOI: 10.1134/S0010508220040139]
¹All-Russian Research Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center, Sarov, 607188, Russian Federation
²Sarov State Physics and Technical Institute, Department of the National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Sarov, 607186, Russian Federation
³Alekseev Nizhny Novgorod State Technical University (NNSTU), Nizhny Novgorod, 603950, Russian Federation
⁴Institute for Problems in Mechanical Engineering, Russian Academy of Sciences, Nizhny Novgorod, 603024, Russian Federation

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¹Zhou, Y.,^1,2Irifune, T.
Physics Chemistry of Minerals 47, 37 Link to Article [DOI: 10.1007/s00269-020-01106-6]
¹Geodynamics Research Center, Ehime University, Matsuyama, 790-8577, Japan
²Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550, Japan

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^1,2Li, Y.,^1,2McCausland, P.J.A.,^1,2Flemming, R.L.
Computers and Geoscience 144, 104572 Link to Article [DOI: 10.1016/j.cageo.2020.104572]
¹Department of Earth Sciences, Western University, London, ON N6A 5B7, Canada
²Institute for Earth and Space Exploration, Western University, London, ON N6A 5B7, Canada

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¹Michael P.Lucas,¹Nick Dygert,²Jialong Ren,^2,3Marc A.Hesse,²Nathaniel R.Miller,¹Harry Y.McSween
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.09.010]
¹Department of Earth & Planetary Sciences, University of Tennessee, 1621 Cumberland Ave., 602 Strong Hall, Knoxville, TN 37996
²Department of Geological Sciences, University of Texas at Austin, 2275 Speedway Stop C9000, Austin, TX 78712
³Oden Institute of Computational Sciences and Engineering, University of Texas at Austin, 201 E 24th St., Austin, TX 78712
Copyright Elsevier

Ordinary chondrites (OCs) are variably thermally metamorphosed meteorites thought to originate from at least three different parent bodies (H, L, and LL) in the Main Belt of asteroids. The thermal evolutions of OC parent bodies are frequently explained by the onion shell model; however, a competing hypothesis is the fragmentation-reassembly model. The onion shell model proposes undisrupted, internally heated parent bodies with concentrically stratified thermal structure, and posits that OC petrologic types (i.e., 3 to 6) develop with increasing temperature and burial depth. In this model, petrologic types are inversely correlated with depth in the parent body, and cooling rate. The alternative fragmentation-reassembly model invokes catastrophic collisional disruption of parent bodies that initially possessed onion shell structures, followed by rapid reaccretion of hot fragments, forming rubble pile bodies. Fragmentation would result in fast cooling (quenching) of collisional fragments from the temperature experienced by the parent body at the time of collision. Discrimination between these two models may be possible via investigation of the thermal histories of OCs by application of geothermometry and geospeedometry, which are used to constrain the temperatures and rates through which igneous and metamorphic rock samples cool. Most published cooling rate data for OC parent bodies are based on methods that record rates through low closure temperatures (∼500-200 °C) rather than from peak metamorphic temperatures. Recently, a rare earth element (REE)-in-two-pyroxene thermometer has been shown to establish peak or magmatic temperatures (TREE; Liang et al. [2013]. GCA 102, 246-260) for rocks that cooled at moderate to fast geologic rates. We applied the REE-in-two-pyroxene method to determine peak temperatures for 18 OC samples (mostly type 6), in conjunction with conventional two-pyroxene thermometry (TBKN; Brey and Köhler [1990]. J. Pet. 31, 1353-1378) and Ca-in-olivine thermometry (TCa-Ol; Köhler and Brey [1990]. GCA 54, 2375-2388), to determine closure temperatures and estimate cooling rates for OC parent bodies. Inconsistent with slow cooling rates expected in an onion shell scenario, we obtain fast cooling at rates ≳0.5 °C/y from peak temperatures of ∼900 °C. Corroborating the TREE and TBKN measurements, TCa-Ol suggests that the OCs cooled through TCa-Ol closure temperatures (∼700 to 800 °C) at ∼10-2 to 10-1 °C/y. These cooling rates are three to six orders of magnitude faster than rates determined using methods sensitive to low temperature (≤500 °C) cooling (e.g., metallography, 40Ar–39Ar ages, 244Pu fission track). We developed a novel numerical thermal model that incorporates fragmentation of an initial onion shell body and reassembly into a rubble pile body that reproduces both the fast cooling from high temperatures and the slow cooling through low temperatures observed in chondritic meteorites. We hypothesize that OC parent bodies initially possessed onion shell thermal structures, but later experienced collisional breakup, then reaccreted rapidly to form thermally stable rubble-pile asteroids.