^1,2Lucas T.McClure,²Sean S.Lindsay
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114907]
¹Department of Physics & Astronomy, The University of Tennessee, Knoxville, TN 37916, United States
²Northern Arizona University, Department of Astronomy and Planetary Science, Flagstaff, AZ 86011, United States
Copyright Elsevier

The visible and near-infrared spectra (0.5–2.5 μm) of ordinary chondrite (OC) meteorites are characterized by absorptions at 1 and 2 μm, typically denoted as Band I and Band II, respectively. Previous works have connected parameterization of Band I and Band II, a so-called band parameter analysis (BPA) of mineralogical abundances and chemistry of OC meteorites. In particular, parameters for these determinations include the center of the Band I feature (BIC) and band area ratio (BAR), the ratio of Band II’s area to that of Band I. Through treating BIC as a function of BAR, OCs plot within a region called the “OC-boot,” first shown in Gaffey et al. (1993). The boundaries for the OC-Boot have remained unchanged since their foundational work, and numerous investigations using various different methods have employed the same boundaries for the OC-Boot’s original zoning. By applying the Spectral Analysis Routine for Asteroids (SARA) to >150 spectra of OCs from Brown University’s NASA/Keck Reflectance Experiment Laboratory (RELAB) database, we highlight the issue of the OC-Boot’s dependency on BPAs. Namely, we vary how Band I and Band II are defined to highlight the BPA-dependency by producing band edge-specific OC-Boots that encompass the mineralogical diversity of OCs (H, L, and LL subtypes) with corresponding spectral ranges. We conclude that there is no single canonical OC-boot and suggest that researchers create their own OC-Boot using their specific BPA or select an OC-boot in the literature that most closely matches their methods of determining band parameters.

^1,2Lucas T.McClure,¹Sean S.Lindsay
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114944]
¹Department of Physics & Astronomy, The University of Tennessee, Knoxville, TN 37916, United States
²Northern Arizona University, Department of Astronomy and Planetary Science, Flagstaff, AZ 86011, United States
Copyright Elsevier

The ordinary chondrite boot (OC-Boot) is a diagnostic region generated from spectral analyses of the features caused by electron absorptions in the olivine and orthopyroxene of OCs. In our companion article to this one, McClure & Lindsay (2022a) demonstrated that the boundaries of the OC-Boot are band parameter analysis (BPA) dependent. Here, we highlight how using OC-Boot boundaries that are not derived from a self-consistent BPA analysis can lead to potential misidentification of ordinary chondrite-like asteroid analogs. We compare S-type asteroid spectral band parameters to the OC-Boot defined in McClure & Lindsay (2022a) and the OC-Boot defined in Gaffey et al. (1993). We choose the Gaffey et al. (1993) OC-Boot for this comparison since its use is frequently seen in the literature without updated boundaries. By applying the Spectral Analysis Routine for Asteroids (SARA) to spectra from the MIT-Hawaii Near-Earth Object Spectroscopic (MITHNEOS) Survey, we demonstrate an overlap between the contemporary view of the OC-Boot and OC analogs, showing that a self-consistent OC-Boot framework captures the variation of the Near-Earth asteroids (NEAs) more than the original OC-Boot. In particular, we show the OC-Boots from McClure & Lindsay (2022a) encompass relatively more NEAs. We also apply a set of calibration equations derived using SARA to determine the mineral abundances and compositions for the S-type asteroids. We find that 59.57% of NEAs exhibit LL-like mineralogies and that H-like and L-like mineralogies are exhibited 19.15% and 6.38% of cases, respectively. There are a couple of cases wherein the mineralogies could be in between subtypes and five cases where no subtype designation could be determined. The high-frequency of LL-like mineralogies is in agreement with previous studies on S-type NEAs.

¹Paul H. Warren,²Randy L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13780]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095 USA
²Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri, 63130 USA
Published by arrangement with John Wiley & Sons

We review constraints on the magnitude and possible causes of discrepancies, or at least major disparities, among global and near-global data sets for lunar highland surface composition. When compared with data from other sources, reported mafic mineral abundance results from the Kaguya Spectral Profiler (Kaguya SP) spectral reflectance method for four Apollo 16 soils appear systematically low by a factor of 0.6, or an even more extreme factor (~1/3) if viewed in relation to the soils’ nonglass or CIPW mineralogy. Also, whether evaluated on a global median basis or on the basis of site-by-site comparison (for Apollo 16, Luna 20, and Apollo 17), the compositions found by the Kaguya SP technique show discrepancy, or at least disparity, versus other mafic abundance observations by that same factor of ~1/3. Spectral reflectance does not supply a simple bulk analysis of the target soil. The reflectance mineralogical signal is preponderantly determined by the nonglass fraction, and especially the masswise subordinate 10–20 µm grain size fraction. Literature data show that in anorthositic lunar soil, chemical composition is fractionated, more extremely anorthositic, for the nonglass component compared to the glass component. Also, the grain size fraction (10–20 μm) that most closely matches bulk reflectance has a significantly higher abundance of impact/agglutinitic glass than does the coarser material that dominates the soil mass. The Kaguya SP mafic abundance calibration needs adjustment by a factor of nearly 3 if results are to be interpreted as indicative of the mineralogy of the underlying crust. A claimed detection of several hundred lunar 500 m scale purest anorthosite (PAN; ≥98 vol% plagioclase) locales among millions of spectral reflectance observations is dubious, in part because with large data sets, compositional extremes are inevitably exaggerated as a byproduct of analytical uncertainty. Preponderance of PAN composition is rare among terrestrial layered intrusive anorthosites and is neither required nor expected for the flotation crust of a global magma ocean. Buoyant flotation and compaction would not suffice to yield pure plagioclase unless adcumulus growth was negligible, and trace element contents of ferroan anorthosites show that their mafic silicate components are for the most part of adcumulus, not “trapped melt,” derivation. A PAN-dominated crust would imply a curiously fractionated (low) thorium/aluminum ratio for the crust, an implausibly high mantle/crust Th concentration ratio, and an oddly low Th/Al for the bulk Moon. Remote sensing techniques for planetary regolith composition are not easy to calibrate, particularly near the extremes of composition-space and sensitivity.

^1,2Takafumi Matsui,²Ryota Moriwaki,³Eissa Zidan,¹Tomoko Arai
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13787]
¹Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016 Japan
²Institute for Geo-Cosmology, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016 Japan
³Conservation Center, Grand Egyptian Museum, El Remayah Square, Cairo-Alex. Road, Pyramids, Giza Governorat, Egypt
Published by arrangement with John Wiley & Sons

The Iron Age was the time when people acquired iron processing technology and is generally thought to have begun after 1200 B.C. Some prehistoric iron artifacts made of iron meteorites are dated from the Bronze Age. A nicely preserved meteoritic iron dagger was found in the tomb of King Tutankhamen (1361–1352 B.C.) of ancient Egypt. Yet, its manufacturing method and origin remain unclear. Here, we report nondestructive two-dimensional chemical analyses of the Tutankhamen iron dagger, conducted at the Egyptian Museum of Cairo. Elemental mapping of Ni on the dagger blade surface shows discontinuous banded arrangements in places with “cubic” symmetry and a bandwidth of about 1 mm, suggesting a Widmanstätten pattern. The intermediate Ni content (11.8 ± 0.5 wt%) with the presence of the Widmanstätten pattern implies the source meteorite of the dagger blade to be octahedrite. The randomly distributed sulfur-rich black spots are likely remnants of troilite (FeS) inclusions in iron meteorite. The preserved Widmanstätten pattern and remnant troilite inclusion show that the iron dagger was manufactured by low-temperature (<950 °C) forging. The gold hilt with a few percent of calcium lacking sulfur suggests the use of lime plaster instead of gypsum plaster as an adhesive material for decorations on the hilt. Since the use of lime plaster in Egypt started during the Ptolemaic period (305–30 B.C.), the Ca-bearing gold hilt hints at its foreign origin, possibly from Mitanni, Anatolia, as suggested by one of the Amarna letters saying that an iron dagger with gold hilt was gifted from the king of Mitanni to Amenhotep III, the grandfather of Tutankhamen.

^1,2Andrei A. Shiryaev,³Anton D. Pavlushin,^4,5Alexei V. Pakhnevich,⁶Ekaterina S. Kovalenko,¹Alexei A. Averin,⁷Anna G. Ivanova
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13791]
¹A. N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Leninsky pr. 31 korp. 4, Moscow, 119071 Russia
²Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Moscow, 119017 Russia
³Diamond and Precious Metal Geology Institute, Siberian Branch of RAS, Lenin pr. 39, Yakutsk, 677000 Russia
⁴Paleontological Institute RAS, Profsoyuznaya str. 123, Moscow, 117997 Russia
⁵The Frank Laboratory of Neutron Physics, JINR, Dubna, 141980 Russia
⁶NRC “Kurchatov Institute,”, Kurchatov square 1, Moscow, 123182 Russia
⁷Shubnikov Institute of Crystallography FSRC “Crystallography and Photonics” RAS, Leninsky pr. 53, Moscow, 119333 Russia
Published by arrangement with John Wiley & Sons

An unusual variety of impact-related diamond from the Popigai impact structure—yakutites—is characterized by complementary methods including optical microscopy, X-ray diffraction, radiography and tomography, infrared, Raman, and luminescence spectroscopy providing structural information at widely different scales. It is shown that relatively large graphite aggregates may be transformed to diamond with preservation of many morphological features. Spectroscopic and X-ray diffraction data indicate that the yakutite matrix represents bulk nanocrystalline diamond. For the first time, features of two-phonon IR absorption spectra of bulk nanocrystalline diamond are interpreted in the framework of phonon dispersion curves. Luminescence spectra of yakutite are dominated by dislocation-related defects. Optical microscopy supported by X-ray diffraction reveals the presence of single crystal diamonds with sizes of up to several tens of microns embedded into nanodiamond matrix. The presence of single crystal grains in impact diamond may be explained by chemical vapor deposition–like growth in a transient cavity and/or a seconds-long compression stage of the impact process due to slow pressure release in a volatile-rich target. For the first time, protogenetic mineral inclusions in yakutites represented by mixed monoclinic and tetragonal ZrO2 are observed. This implies the presence of baddeleyite in target rocks responsible for yakutite formation.

¹Guillaume Siron,¹Kohei Fukuda,²Makoto Kimura,¹Noriko T.Kita
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.010]
¹WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
²National Institute of Polar Research, Meteorite Research Center, Midoricho 10-3, Tachikawa, Tokyo 190-8518, Japan
Copyright Elsevier

Chondrules in ordinary chondrites are considered to form in high density environments, likely related to the evolution of protoplanets and large planetesimals. In order to determine the timing of their formation at high time resolution (≤0.1 Ma), we conducted high precision Al-Mg chronology of 17 porphyritic chondrules from 6 different unequilibrated ordinary chondrites (UOCs) of low petrologic subtypes (3.00-3.05). Detailed petrology, mineralogy, and oxygen isotope ratios of individual chondrules were also obtained that include 10 additional chondrules without Al-Mg ages. Seventeen chondrules for Al-Mg chronology consist of 14 chondrules with plagioclase (An₁-An₈₇) and three chondrules with Na-rich glassy mesostasis, all of which have high ²⁷Al/²⁴Mg ratios (30-3,000). The inferred initial (²⁶Al/²⁷Al)₀ ratios range between (6.5 ± 0.6)×10^–6 to (9.5 ± 1.0)×10^–6, corresponding to chondrule formation ages of 1.74 ± ^0.12/_0.11 Ma to 2.13 ± 0.09 Ma after CAIs, which have a canonical (²⁶Al/²⁷Al)₀ ratio of 5.25×10^–5. Six albite-bearing chondrules (An_<30) show a much more restricted ages range, spanning between 2.00 ± ^0.11/_0.10 Ma and 2.07 ± ^0.11/_0.10 Ma. Including 14 anorthite-bearing chondrules studied previously, chondrules in ordinary chondrites have a restricted range of formation ages from 1.8 Ma to 2.2. Ma after CAIs.

Based on the newly acquired oxygen isotope data and previous high precision studies, chondrules in L and LL chondrites do not show systematic difference in their δ¹⁸O and δ¹⁷O signatures. Majority of plagioclase-bearing chondrules studied for Al-Mg chronology show similar oxygen isotope ratios to those of glass-bearing chondrules. There is no obvious difference in Al-Mg ages of chondrules between L and LL chondrites. Thus, chondrules in L and LL chondrites would have formed in common environments and processes, though they accreted to two separate parent bodies by 2.2 Ma after CAIs, which timing is consistent with the proposed thermal model for ordinary chondrite parent bodies. Onset of chondrule formation at 1.8 Ma after CAIs may be caused by the delay of Jupiter formation or the formation of protoplanets in ordinary chondrite chondrule forming regions if chondrules formed by large scale disk shock or impact jetting of protoplanets. Alternatively, early formed chondrules would not be preserved before 1.8 Ma if chondrules formed by the impacts of molten planetesimals.

^1,2,3Jangmi Han,⁴Changkun Park,¹Adrian J.Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.007]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
²Lunar and Planetary Institute, USRA, 3600 Bay Area Boulevard, Houston, TX 77058, USA
³Astromaterials Research and Exploration Science, NASA Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058, USA
⁴Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 21990, South Korea
Copyright Elsevier

Amoeboid olivine aggregates (AOAs) from the Kainsaz CO3.2 chondrite were analyzed using transmission electron microscopy in order to gain a more complete understanding of thermal metamorphism on the parent body and the role of fluids during metamorphic heating. The Kainsaz AOAs are dominated by strongly zoned, fine-grained, olivine grains (Fa2-31) with heterogeneous Fe enrichments along the grain boundaries, which are interpreted as the result of Fe2+-Mg2+ interdiffusion with the matrix during thermal metamorphism. However, our diffusion calculations show that such AOA olivine zoning and compositions cannot be produced by a simple diffusional exchange during metamorphic heating, unlike chondrule olivine zoning and compositions. In addition, fine-grained ferroan olivine overgrowths occur heterogeneously in crystallographic continuity with olivines on the AOA exteriors. The overgrowths (Fa33-36) are compositionally distinct from the underlying AOA olivines and are not fully equilibrated with the matrix olivines (Fa∼20-55). The ferroan olivine overgrowths likely formed by precipitation from fluids in an epitaxial relationship with forsteritic olivine on the edges of AOAs. Texturally and compositionally diverse chromite grains are also observed along olivine grain boundaries, in olivine grains, and in pore spaces between olivine grains. They share a similar crystallographic orientation relationships with adjacent olivine, suggestive of their formation by exsolution and/or epitaxial growth. Collectively, these observations provide evidence for the mobilization of Fe, Mg, Si, Cr, and Al in the presence of fluids along olivine grain boundaries and into olivine grains during thermal metamorphism. We conclude that in Kainsaz AOAs, the strong zonation development in individual olivine grains and the formation of ferroan olivine overgrowths and chromite grains were a fluid-driven process that occurred at relatively low temperatures (<500℃), during the cooling history of the CO3 chondrite parent body, following the peak of thermal metamorphism.

¹Cocean A.,¹Postolachi C.,^1,2Cocean G.,³Bulai G.,¹Munteanu B.,^1,4Cimpoesu N.,¹Cocean I.,¹Gurlui S.
Applied Sciences 12, 983 Link to Article [DOI 10.3390/app12030983]
¹Faculty of Physics, Alexandru Ioan Cuza University of Iasi, 11 Carol I Bld, Iasi, 700506, Romania
²Rehabilitation Hospital Borsa, 1 Floare de Colt Street, Borsa, 435200, Romania
³Integrated Center of Environmental Science Studies in the North-Eastern Development Region (CERNESIM), Department of Exact and Natural Sciences, Institute of Interdisciplinary Research, Alexandru Ioan Cuza University of Iasi, Iasi, 700506, Romania
⁴Faculty of Material Science and Engineering, Gheorghe Asachi Technical University of Iasi, 59A Mangeron Bld, Iasi, 700050, Romania

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¹Seppe Lampe et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.02.008]
¹Analytical-, Environmental-, and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
Copyright Elsevier

Micrometeorites experience varying degrees of evaporation and mixing with atmospheric oxygen during atmospheric entry. Evaporation due to gas drag heating alters the physicochemical properties of fully melted cosmic spherules (CSs), including the size, chemical and isotopic compositions and is thus expressed in its chemical and isotopic signatures. However, the extent of evaporation and atmospheric mixing in CSs often remains unclear, leading to uncertainties in precursor body identification and statistics. Several studies have previously estimated the extent of evaporation based on the contents of major refractory elements Ca and Al in combination with the determined Fe/Si atomic ratios. Similarly, attempts have been made to design classification schemes based on isotopic variations. However, a full integration of any previously defined chemical classification schemes with the observed isotopic variability has not yet been successful. As evaporation can lead to both chemical and isotope fractionation, it is important to verify whether the estimated degrees of evaporation based on chemical and isotopic proxies converge. Here, we have analysed the major and trace element compositions of 57 chondritic (mostly V-type) CSs, along with their Fe isotope ratios. The chemical (Zn, Na, K or CaO and Al2O3 concentrations) and δ56Fe isotope fractionation measured in these particles show no correlation. The interpretation of these results is twofold: (i) isotopic and chemical fractionation are governed by distinct processes or (ii) the proxies selected for chemical and isotope fractionation are inadequate. While the initial Fe isotopic ratios of chondrites are constrained within a relatively narrow range (0.005 ± 0.008‰ δ56Fe), the chemical compositions of CSs display larger variability. Cosmic spherules are thus often not chemically representative of their precursor bodies, due to their small size. As oxygen isotopes are commonly used to refine the precursor bodies of meteorites, triple oxygen isotope ratios were measured in thirty-seven of the characterized CSs. Based on the relationship between δ18O and δ57Fe, the evaporation effect on the O isotope system can be calculated, which allows for a more accurate parent body determination. Using this correction method, two ‘Group 4’ spherules with strongly variable degrees of isotope fractionation (δ56Fe of ∼1.0‰ and 29.1‰, respectively) could be distinguished. Furthermore, it was observed that all CSs that probably have a OC-like heritage underwent roughly the same degree of atmospheric mixing (∼8‰ δ18O). This highlights the potential of including Fe isotope measurements to the regular methodologies applied to CS studies.

^1,2Tim Cunningham,^1,2Peter J. Wheatley,^1,2Pier-Emmanuel Tremblay,^1,2Boris T. Gänsicke,³George W. King,^4,5Odette Toloza,^1,2Dimitri Veras
Nature 602, 219-222 Link to Areticle [DOI https://doi.org/10.1038/s41586-021-04300-w]
¹Department of Physics, The University of Warwick, Coventry, UK
²Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK
³Department of Astronomy, University of Michigan, Ann Arbor, MI, USA
⁴Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso, Chile
⁵Millennium Nucleus for Planet Formation (NPF), Valparaíso, Chile

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