¹Sheng Shang,^1,2Hejiu Hui,²Yueheng Yang,¹Tianyu Chen
Earth and Planetary Science Letters 581, 117413 Link to Article [https://doi.org/10.1016/j.epsl.2022.117413]
¹State Key Laboratory for Mineral Deposits Research & Lunar and Planetary Science Institute, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
²CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
³State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Copyright Elsevier

The observations of Martian orbiters and rovers have suggested that there were fluids on the surface of early Mars. However, the geochemical properties of those fluids are unclear. The Martian regolith breccia meteorites (MRB), the source materials of which are thought to have formed at 4.4 Ga, may have recorded interactions with fluids on Mars. Here, we have analyzed the in situ Sm-Nd isotopic compositions and trace element contents of apatite in MRB and have obtained a Sm-Nd isochron age of 1490±480 Ma. This young age indicates that the MRB apatites were altered by fluids and have exchanged trace elements with fluids. The very negative initial Nd, combined with the previously reported positive δD and Cl in the MRB apatites, indicate that Martian fluids originated from a geochemically enriched reservoir in the crust. The large ranges of rare earth element abundance (ΣREE) and of the chondrite normalized ratio of La and Yb [(La/Yb)N] indicate the chemical complexity of the fluids that interacted with the apatites in the MRB. The apatite REE compositions were used to further determine the pH values of Martian fluids equilibrated with the MRB apatites, which varied from ∼3 to ∼8. The apatite X-site Cl contents indicate that the Cl contents in Martian fluids in equilibrium with the MRB apatites at 400 °C and 1 bar could be up to 1857 ppm, within the range of terrestrial hydrothermal fluids. Combined with previously reported geochemical data from Martian meteorites, our study suggests that fluids may have been present throughout the early geological history of Mars.

¹Lars E. Borg,¹Gregory A. Brennecka,^1,2Thomas S. Kruijer
Proceedings of the National Academy of Sciences of the United States of America (PNAS) (In Press) Link to Article [https://doi.org/10.1073/pnas.2115726119]
¹Nuclear and Chemical Science Division, Lawrence Livermore National Laboratory, Livermore, CA 94550;
²Department of Solar System, Impacts & Meteorites, Museum fur Naturkunde, Berlin 10115, Germany

The origin of volatile species such as water in the Earth–Moon system is a subject of intense debate but is obfuscated by the potential for volatile loss during the Giant Impact that resulted in the formation of these bodies. One way to address these topics and place constraints on the temporal evolution of volatile components in planetary bodies is by using the observed decay of ⁸⁷Rb to ⁸⁷Sr because Rb is a moderately volatile element, whereas Sr is much more refractory. Here, we show that lunar highland rocks that crystallized ∼4.35 billion years ago exhibit very limited ingrowth of ⁸⁷Sr, indicating that prior to the Moon-forming impact, the impactor commonly referred to as “Theia” and the proto-Earth both must have already been strongly depleted in volatile elements relative to primitive meteorites. These results imply that 1) the volatile element depletion of the Moon did not arise from the Giant Impact, 2) volatile element distributions on the Moon and Earth were principally inherited from their precursors, 3) both Theia and the proto-Earth probably formed in the inner solar system, and 4) the Giant Impact occurred relatively late in solar system history.

¹Rajkrishna Dutta et al. (>10)
Proceedings of the National Academy of Sciences of the United States of America (PNAS) (in Press) Link to Article [https://doi.org/10.1073/pnas.2114424119]
¹Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015
²Department of Geosciences, Princeton University, Princeton, NJ 08544

Mg₂GeO₄ is important as an analog for the ultrahigh-pressure behavior of Mg₂SiO₄, a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computations. The experimental results are consistent with the formation of a phase with disordered Mg and Ge, in which germanium adopts eightfold coordination with oxygen: the cubic, Th₃P₄-type structure. DFT computations suggest partial Mg-Ge order, resulting in a tetragonal I4¯2d structure indistinguishable from I4¯3d Th₃P₄ in our experiments. If applicable to silicates, the formation of this highly coordinated and intrinsically disordered phase may have important implications for the interior mineralogy of large, rocky extrasolar planets.

¹Arianna E. Gleason et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13785]
¹SLAC National Accelerator Laboratory, Menlo Park, California, 94025 USA
Published by arrangement with John Wiley & Sons

Meteor impacts can induce unique pressure-dependent structural changes in minerals due to the propagation of shock waves. Plagioclase—ubiquitous throughout the Earth’s crust, extraterrestrial bodies, and meteorites—is commonly used for reconstructing the impact history and conditions of the parent bodies. However, there have been unresolved inconsistencies in the interpretation of shock transformations across previous studies: The pressure at which amorphization begins and the process by which it occurs is the subject of ongoing debate. Here, we utilize time-resolved in situ X-ray diffraction (XRD) to probe the phase transformation pathway of plagioclase during shock compression at a sub-nanosecond timescale. Direct amorphization begins at pressures much lower than what was previously assumed, just above the Hugoniot elastic limit of 5 GPa, with full amorphization to a high-density amorphous phase, observed at 32(10) GPa and 20 ns. Upon release, the material partially recrystallizes back into the original structure, demonstrating a memory effect.

¹Zhongwu Lan,¹Ross N.Mitchell,²Thomas M.Gernon,³Adam R.Nordsvan
Earth and Planetary Science Letters 581, 117407 Link to Article [https://doi.org/10.1016/j.epsl.2022.117407]
¹State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²School of Ocean and Earth Science, University of Southampton, Southampton SO22 4JR, UK
³Department of Earth Sciences, University of Hong Kong, Pokfulam, Hong Kong
Copyright Elsevier

The ca. 717 Ma low-latitude Sturtian “snowball Earth” glaciation lasted ∼56 Myr. However, sedimentological evidence for transient, open ocean conditions during the glaciation appears to contradict the concept of a global deep freeze. We demonstrate multiple lines of geologic evidence from five continents for a temporary, localized sea-ice retreat during the middle of the Sturtian glaciation, which coincides with one, perhaps two, asteroid impacts, and arguably more terrestrial impacts as inferred from the lunar impact record. The well-dated Jänisjärvi impact (ca. 687 Ma) is synchronous with repeated volcanic ash falls whose deposition is most parsimoniously interpreted to indicate a partially ice-free ocean. Temporary greenhouse warming caused by the vaporization of sea ice can explain localized glacial retreat within restricted seaways between these continents, where ice flow would have been constricted and sea ice thinnest before impact.

^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.