¹L.Mandon,^2,3P.Beck,¹C.Quantin-Nataf,¹E.Dehouck,⁴A.Pommerol,⁴Z.Yoldi,⁴R.Cerubini,¹L.Pan,¹M.Martinot,⁵V.Sautter
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114517]
¹Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, F-69622 Villeurbanne, France
²Université Grenoble-Alpes, CNRS, IPAG, UMR, 5274 Grenoble, France
³Institut Universitaire de France, France
⁴Space Research & Planetary Sciences Division, Physikalisches Institut, Universität Bern, Bern, Switzerland
⁵Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, 75005 Paris, France
Copyright Elsevier

In the next decade, two rovers will characterize in situ the mineralogy of rocks on Mars, using for the first time near-infrared reflectance spectrometers: SuperCam onboard the Mars 2020 rover and MicrOmega onboard the ExoMars rover, although this technique is predominantly used in orbit for mineralogical investigations. Until successful completion of sample-return missions from Mars, Martian meteorites are currently the only samples of the red planet available for study in terrestrial laboratories and comparison with in situ data. However, the current spectral database available for these samples does not represent their diversity and consists primarily of spectra acquired on finely crushed samples, albeit grain size is known to greatly affect spectral features. Here, we measured the reflected light of a broad Martian meteorite suite as a means to catalogue and characterize their spectra between 0.4 and 3 μm. These measurements are achieved using a point spectrometer acquiring data comparable to SuperCam, and an imaging spectrometer producing hyperspectral cubes similarly to MicrOmega. Our results indicate that point spectrometry is sufficient to discriminate the different Martian meteorites families, to identify their primary petrology based on band parameters, and to detect their low content in alteration minerals. However, significant spectral mixing occurs in the point measurements, even at spot sizes down to a few millimeters, and imaging spectroscopy is needed to correctly identify the various mineral phases in the meteorites. Additional bidirectional spectral measurements on a consolidated and powdered shergottite confirm their non-Lambertian behavior, with backward and suspected forward scattering peaks. With changing observation geometry, the main absorption strengths show variations up to ~10–15%. The variation of reflectance levels is reduced for the rock surface compared to the powder. All the spectra presented are provided in the supplementary data for further comparison with in situ and orbital measurements.

¹Lingzhi Sun,¹Paul G. Lucey,¹G. Jeff Taylor
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2020JE006445]
¹Hawai‘i Institute of Geophysics and Planetology, Dept. of Earth Sciences, University of Hawai‘i at Manoa, 1680 East‐West Rd., Honolulu, Hi, 96822 USA
Published by arrangement with >John Wiley & Sons

Although lunar soils contain rock and mineral components from the breakdown of a mixture of rock types, a classification based on the abundances of the major silicate minerals plagioclase, olivine, low‐Ca pyroxene (LCP) and high‐Ca pyroxene can be used to evaluate the major compositional classes that are represented within a given soil. We studied the compositional classes for Apollo 15, 16 and 17 soil samples based on the mineral modal abundances derived by X‐ray diffraction (XRD). Using the XRD results as a ground truth, we determined the compositional classes of the Apollo 15, 16 and 17 sampling stations using mineral maps from the Kaguya Multiband Imager (MI), then mapped areas having compositional classes similar to the sampling stations on regional and global scales. Global distribution of compositional classes was also mapped using MI mineral maps, and the major compositional classes of lunar nonmare surfaces are noritic anorthosite (40 %), anorthositic norite (24 %), and anorthosite (23 %). Our maps show that the lunar highlands and the South Pole‐Aitken (SPA) basin are enriched with noritic materials, indicating the widespread occurrence of LCP‐rich and olivine‐poor assemblages. In contrast to the SPA basin and the highlands, the basin rings of Serenitatis, Crisium, Humorum, Nectaris, Orientale and Hertzsprung exhibit higher olivine/pyroxene ratios (>2), and we interpret this signature as reflecting a contribution from olivine‐rich upper mantle components.

¹Paul Frossard,²Zhiguo Guo,²Mary Spencer,¹Maud Boyet,^2,3Audrey Bouvier
Earth and Planetary Science Letters 566, 116968 Link to Article [https://doi.org/10.1016/j.epsl.2021.116968]
¹Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France
²Department of Earth Sciences, University of Western Ontario, N6A 5B7 London, Ontario, Canada
³Bayerisches Geoinstitut, Universität Bayreuth, 95447 Bayreuth, Germany
Copyright Elsevier

Heterogeneity in isotopic compositions within the protoplanetary disc has been demonstrated for a number of elements measured in extra-terrestrial materials, mostly based on chondrite meteorite analyses. However, precise 182Hf-182W and 26Al-26Mg ages of iron meteorites, achondrites, and chondrules show that chondrites accreted later than achondrites and therefore do not strictly represent the early (<2 Ma) solar system composition. Here we present the Nd mass-independent stable isotopic compositions of a suite of diverse achondrites to better constrain the Nd isotope evolution of the early solar system. Carbonaceous (C) achondrites are indistinguishable from their chondritic counterpart. However, early formed planetesimals as sampled by silicate-rich non-carbonaceous (NC) achondrite meteorites have higher 145Nd/144Nd and 148Nd/144Nd ratios (3.9 < Nd < 11.0 and 9.1 < Nd < 17.9 in part per million deviation, or Nd) compared to NC chondrites (2.7 < Nd < 3.3 and 2.2 < Nd < 8.1). Moreover, the three terrestrial planets for which we have samples available (Earth, Mars, and the Moon) as well as the silicate inclusions from the non-magmatic IIE iron meteorite Miles present a systematic deficit in Nd and Nd compared to early-formed NC achondrites. Unlike chondrites, the Nd anomalies in achondrites are not correlated to the heliocentric distance of accretion of their respective parent bodies as inferred from redox conditions. Chronological constraints on planetesimal accretion suggest that Nd (and other elements such as Mo and Zr) nucleosynthetic compositions of the inner part of the protoplanetary disc significantly changed around 1.5 Ma after Solar System formation due to thermal processing of dust in the protoplanetary disc. This relatively late event coincides with the beginning of chondrule formation or at least their preservation. Terrestrial planets formed subsequently by a complex accretion regime during several million years. Therefore, two scenarios are envisioned considering the reported Nd isotope composition of early planetesimals: 1) Terrestrial planets accreted mostly chondritic material similar in composition to enstatite chondrites, or 2) early planetesimals constitute substantial parts of terrestrial planets building blocks mixed with highly thermally processed material enriched in s-process, still unsampled by meteorites.

¹Hisayoshi Yurimoto,²Alan E. Rubin,³Shoichi Itoh,⁴John T. Wasson
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13652]
¹Isotope Imaging Laboratory (IIL), Natural History Sciences, Hokkaido University, Sapporo, 001–0021 Japan
²Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095–1567 USA
³Department of Earth and Planetary Sciences, Kyoto University, Kyoto, 606–8502 Japan
⁴Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095–1567 USA
Published by arrangement with John Wiley & Sons

We studied a unique super‐refractory inclusion with a core‐mantle structure from CO3.0 Yamato 81020 by secondary ion mass spectrometry, electron microprobe, and scanning electron microscope techniques. The core consists largely of hibonite and nonstoichiometric Al‐rich spinel indicating formation as a liquid at an exceptionally high temperature (>1900 °C). The mantle consists almost entirely of melilite with gehlenitic compositions (ranging from Åk2 to Åk25). The oxygen‐ and magnesium‐isotopic compositions of the core and mantle are very different; typically, Δ17O (≡δ17O − 0.52 δ18O) ~–26‰ and ƒMg (mass fractionation of Mg isotopes) ~10‰/amu in the core and Δ17O ~–7‰ and ƒMg ~1‰/amu in most of the mantle. The chemical and O, Mg‐isotopic data indicate that the core and mantle formed in separate events, and that the melilite now in the core was formed during the mantle‐melting event, probably filling preexisting voids and surficial cavities. Analyses of core and mantle phases plot along a single 26Al‐26Mg isochron with initial (26Al/27Al)0 corresponding to 4.8 ± 1.0 (±2σ) × 10–5, suggesting a similar formation age to normal CAIs in chondrites.

¹Stella Rombeck,¹Christian Vollmer,²Julia Roszjar,³Adam R. Sarafian,¹Stephan Klemme
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13651]
¹Institut für Mineralogie, Westfälische Wilhelms‐Universität Münster, Corrensstrasse 24, 48149 Münster, Germany
²Department of Mineralogy and Petrography, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria
³Corning Incorporated, Science and Technology Division, 21 Lynn Morse Rd., Painted Post, New York, 14870 USA
Published by arrangement with John Wiley & Sons

Some basaltic eucrites and basaltic lithologies in howardites derived from the asteroid 4 Vesta exhibit unusual secondary veinlet textures consisting mostly of fayalitic olivine and Fe‐enrichments within pyroxenes. Recent studies discussed the formation of these Fe‐rich phases either by interaction with a vapor and/or liquid phase (metasomatism), or by a high‐temperature melting process. We therefore performed a series of heating and hydrothermal experiments with liquids of different compositions on natural pyroxene crystals (augite and orthopyroxene) to evaluate these contrasting hypotheses. The results of the heating experiments show that incongruent melting of pyroxenes at about 1070 °C causes textures that are very similar to those observed in the meteorites. We conclude that a part of the natural secondary veins might be explained by heating processes at similar temperatures. The hydrothermal experiments with aqueous liquids of different Fe‐enriched compositions clearly indicate ion exchange reactions resulting in partial Fe‐enrichments of the pyroxene. Interestingly, these Fe‐enrichments occurred independent of the Fe content of the liquid, which can be explained by an internal origin of Fe from the pyroxenes. In one hydrothermal experiment of augite with Fe‐oxalate solution, deposition of fayalitic olivine was observed. From our experimental observations, we conclude that aqueous liquids are plausible candidates for explaining the deposition of Fe‐enrichments and fayalitic olivine inside the fractures of pyroxene. However, we cannot rule out a high‐temperature melting process slightly above the peritectic point of pyroxene to explain a fraction of observed secondary Fe‐enrichments.

¹Stefan Farsang,²Ian A. Franchi,^,Xuchao Zhao,³Timothy D. Raub,⁴Simon A.T. Redfern,^2,5Monica M. Grady
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13647]
¹Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ UK
²School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
³School of Earth & Environmental Sciences, University of St Andrews, Irvine Building, St Andrews, KY16 9AL UK
⁴Asian School of the Environment, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798 Singapore
⁵Department of Earth Sciences, Natural History Museum, Cromwell Rd, London, SW7 5BD UK
Published by arrangement with John Wiley & Sons

The paragenesis of carbonates in the Cold Bokkeveld CM chondrite is determined from a detailed petrographic, chemical, spectroscopic, and isotopic study of nine associations of carbonates (aragonite, calcite, and dolomite) with other secondary minerals that occur within the meteorite. Our study reveals the existence of carbonates displaying petrographic features that are distinct from those of type 1 and type 2 carbonates commonly observed in CM2 meteorites. These include carbonates interstitial to octahedral magnetite crystals, for which a new designation of “type 1c” is suggested. The O isotopic values of dolomite (δ¹⁸O ranging from +21.1 to +25.8‰ and Δ¹⁷O from −4.9 to −4.0‰) are similar to those measured in dolomites from other CM chondrites. The presence of complex carbonates with a CaCO₃ core and Mg‐enriched rim implies several generations of fluids and/or their evolving composition on the CM parent body(ies). Petrographic characteristics indicate at least six stages of potentially overlapping carbonate and phyllosilicate formation events. We show that type 1 and type 2 calcite have distinct Raman spectral characteristics. Type 1 calcite is characterized by very broad peaks, whereas type 2 calcite displays narrow peaks similar to those of typical abiotic terrestrial calcite, suggesting high crystallinity. A carbonate Raman spectrum showing features characteristic of both aragonite and calcite likely documents an aragonite‐calcite phase transition. Raman spectroscopy also reveals the presence of organic matter in the majority of carbonates. This indicates that organic carbon was mobilized by aqueous fluids for extended periods.

¹Annarita Franza,²Marco Morelli,²Daniela Faggi,^1,3Giovanni Pratesi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13654]
¹Department of Earth Sciences, University of Firenze, via G. La Pira 4, 50122 Florence, Italy
²Fondazione PARSEC, Via Galcianese 20/h, 59100 Prato, Italy
³INAF‐IAPS, Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133 Rome, Italy
Published by arrangement with John Wiley & Sons

This work focuses on the historical and scientific investigation of a presumed meteorite fall that occurred in the Sicilian township of Marsala in 1834. Preliminary studies have classified this phenomenon as a “doubtful meteorite.” This term describes, according to the Nomenclature Committee of the Meteoritical Society, an object for which there was significant uncertainty over whether it was a real meteorite or, in some cases, whether it ever existed. Thanks to the analysis of untapped sources, the first objective of this work is to clarify the nature of the event. Subsequently, the results of the minero‐chemical analyses that were performed, in 1835, on two fragments recovered after the event are discussed for the first time. This work then shows the collecting history of one of the presumed meteorite specimens. Based on the results presented here, this work highlights the role of doubtful meteorites as a fundamental resource for the history of meteoritics and meteorite collecting as well as for studying the processes that have led to the scientific study of meteorites.

¹Aryavart Anand,^1,2Jonas Pape,¹Martin Wille,¹Klaus Mezger
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.04.029]
¹Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland
²Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
Copyright Elsevier

The 53Mn-53Cr isotope systematics in ordinary chondrites constrains the accretion and thermal history of their parent bodies. Mineralogical observations and olivine-spinel geothermometry suggest that chromite in ordinary chondrites formed during prograde thermal metamorphism with the amount of chromite increasing with petrologic grades in type 3 to type 6 ordinary chondrites. Assuming a chondritic evolution of the respective parent bodies, 53Cr/52Cr model ages for chromite range from to Ma after the formation of calcium-aluminium-rich inclusions (CAIs). Chromite and silicate-metal-sulphide isochrons define an age range from to Ma. Both chromite model ages and isochron ages correlate with the petrological grade of the samples, which is consistent with an onion-shell structure of the chondrite parent bodies. The study shows that unlike the isochron ages, which are prone to impact-related disturbances or partial re-equilibration during cooling from high temperatures, the chromite model ages are not easily affected by thermal metamorphism or later events and yield robust mineral growth ages. The results are consistent with a homogenous distribution of 53Mn and an initial canonical 53Mn/55Mn = 6.28 x 10-6. The estimated closure temperatures for the Mn-Cr system in chromites range from ∼760 °C for type 6 to ∼540-620 °C for type 3 ordinary chondrites. The high closure temperatures estimated for type 3 and type 6 ordinary chondrites imply that the chromite ages correspond to the peak metamorphic temperature reached during the thermal history of the chondrite parent bodies. The oldest chromite model age obtained for type 3 samples along with the established Al-Mg chondrule formation ages constrain the accretion of the parent bodies to > 2.1 Ma after CAI formation, implying that planetesimal accretion immediately followed chondrule formation.