¹Konstantin M. Ryazantsev,²Alexander N. Krot,³Chi Ma,¹Marina A. Ivanova,¹Cyril A. Lorenz,⁴Vasiliy D. Shcherbakov
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14238]
¹Vernadsky Institute of Geochemistry of the Russian Academy of Sciences, Moscow, Russia
²Hawai’i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai’i at Mānoa, Honolulu, Hawai’i, USA
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁴Lomonosov Moscow State University, Moscow, Russia
Published by arrangement with John Wiley & Sons

Isolated corundum grains and corundum ± Mg-deltalumite [(Al,Mg)(Al,◻)2O4] ± hibonite assemblages were investigated in the CH3.0 metal-rich carbonaceous chondrite Sayh al Uhaymir (SaU) 290. Although very refractory inclusions containing abundant Zr- and Sc-rich oxides and silicates, hibonite, grossite, or perovskite have been previously described in CH chondrites, this is the first discovery of corundum and Mg-deltalumite in CHs and the first discovery of Mg-deltalumite in nature. Magnesium-deltalumite can be indexed by the Fd3m spinel-type structure and gives a perfect fit to the synthetic Al-rich spinel cells. Corundum-Mg-deltalumite grains, 5–20 μm in size, are occasionally rimmed by a thin layer of hibonite replacing corundum. Some corundum grains contain tiny inclusions of ultrarefractory Zr,Sc-rich minerals and platinum-group element (PGE) nuggets. All corundum, hibonite, and Mg-deltalumite grains studied have 16O-rich compositions (average Δ17O ± 2SD = −22 ± 3‰). Two corundum grains show evidence for significant mass-dependent fractionation of oxygen isotopes: Δ18O ~ +34‰ and ~ +19‰. We suggest that the SaU 290 corundum-rich objects were formed by evaporation and/or condensation in a hot nebular region close to the proto-sun where the ambient temperature was close to the condensation temperature of corundum. A corundum grain with tiny inclusions of Zr- and Sc-rich phases and PGE metal nuggets recorded formation temperatures higher than the condensation temperature of corundum. Two corundum-rich objects with highly fractionated oxygen isotopes must have crystallized from a melt that experienced evaporation. Corundum grains corroded by hibonite recorded gas–solid interaction in this region during its cooling. The Mg-deltalumite ± corundum ± hibonite objects were formed by rapid crystallization of high-temperature (>2000°C) refractory melts. The lack of minerals with condensation temperatures below those of corundum and hibonite in the SaU 290 corundum-rich objects suggests that after formation, these objects were rapidly removed from the hot nebular region by disk wind and/or by turbulent diffusion and disk spreading.

¹Haiyang Luo,¹Lidunka Vočadlo,^1,2John Brodholt
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.07.002]
¹Department of Earth Sciences, University College London, London, UK
²Center for Planetary Habitability, University of Oslo, Oslo, Norway
Copyright Elsevier

Fe isotope variations in rocky bodies reveal fundamental information about planetary evolution. However, experimental results have come to contradictory conclusions on the equilibrium Fe isotope fractionation between metal and silicate during core-mantle differentiation. Many different processes, including evaporation, core formation, partial melting and disproportion of mantle silicate, have been consequently proposed to explain the observed Fe isotope variations in rocky solar system bodies. Here we perform ab initio molecular dynamics simulations and find that the anharmonicity in iron strongly decreases the force constant of Fe at low pressures (<∼50 GPa), which even reverses the equilibrium Fe isotope fractionation between metal and silicate. We conclude that pyrolitic melt is always enriched in heavy Fe isotopes relative to liquid Fe-alloys, no matter what pressure. Therefore core-mantle differentiation will play a significant role in explaining the heavy Fe isotope compositions of the mantles of some rocky bodies (e.g., Earth, the ureilite parent body, and possibly the asteroid Vesta). As all previously proposed processes for Fe isotope fractionation can only enrich the mantle-derived rocks in heavy Fe isotopes, the near/sub-chondritic Fe isotope signatures of Mars and the aubrite parent body thus imply that iron sulfide enriched in light Fe isotopes may significantly contribute to the iron components of those meteoritic samples.

¹Brendan J. Orenstein,^2,3,4Michael W.M. Jones,¹David T. Flannery,⁵Austin P. Wright,⁶Scott Davidoff,⁷Michael M. Tice,¹Luke Nothdurft,¹Abigail C. Allwood
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116202]
¹School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, QLD 4000, Australia
²Central Analytical Research Facility, Queensland University of Technology, Brisbane, QLD 4000, Australia
³School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4000, Australia
⁴Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4000, Australia
⁵School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
⁶Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
⁷Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA
Coypright Elsevier

Elemental quantification instruments for planetary missions provide a capability for in-situ identification of mineral phases via stoichiometry, an essential step in petrological investigations. X-ray fluorescence (XRF) has been employed for this purpose by multiple generations of Mars rovers (i.e., Pathfinder, Spirit and Opportunity, Curiosity and Perseverance). The Planetary Instrument for X-ray Lithochemistry (PIXL) aboard Perseverance rasters a micro-focused X-ray beam to generate micron-mm-sized maps illustrating variations in elemental composition and allowing mission scientists to identify rock components (i.e., sedimentary grains, veins and igneous crystals). Energy-dispersive X-ray diffraction can also be detected with PIXL and can be used as an additional constraint on component boundaries, providing PIXL with the capability to map monocrystalline regions in-situ. Here we introduce and apply a new method where each diffraction peak is partitioned independently according to its energy, using the instrument geometry to inform consistent partitioning. Applying this method to datasets acquired from the Dourbes abrasion patch in the Séítah formation of Jezero crater, Mars, reveals monocrystalline regions that were hidden using previous methods. This application of the technique allows faster and more accurate visualization of petrographic textures in future PIXL datasets, in particular those with rock components that are not easily separable using stoichiometry alone.

¹Jean-Pierre Lorand,¹Sylvain Pont,¹Roger H. Hewins,¹Brigitte Zanda
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14233]
¹Institut de Minéralogie, Physique de la matière et Cosmochimie, et Muséum National d’Histoire Naturelle, UMR CNRS 7590, Sorbonne Université, Paris, France
Copyright Elsevier

Northwest Africa (NWA) 14672, the most highly shocked Martian meteorite so far, has experienced >50% melting, compatible with peak pressure >~65 Gpa, at a transition stage 6/7. Despite these extreme shock conditions, the meteorite still preserves a population of “large” Fe sulfide blebs from the pre-shock igneous assemblage. These primary blebs preserve characteristics of basaltic shergottites in term of modal abundance, preferential occurrence in interstitial pores along with late-crystallized phases (ilmenite, merrillite), and Ni-free pyrrhotite compositions. Primary sulfides underwent widespread shock-induced remelting, as indicated by perfect spherical morphologies when embedded in fine-grained silicate melt zones and a wealth of mineral/glass/vesicle inclusions. Extensive melting of Fe-sulfides is consistent with the decompression path experienced by NWA 14672 after the peak shock pressure at ~70 GPa. Primary sulfides acted as preferential sites for nucleation of vesicles of all sizes which helped sulfur degassing during decompression, leading to partial resorption of Fe-sulfide blebs and reequilibration of pyrrhotite metal/sulfur ratios (0.96–0.98) toward the low oxygen fugacity conditions indicated by Fe-Ti oxides hosted in fine-grained materials. The extreme shock intensity also provided suitable conditions for widespread in situ redistribution of igneous sulfur as micrometric globules concentrated in glassy portions of fine-grained lithologies. These globules exsolved early on quenching, allowing dendritic skeletal Fe-Ti oxide overgrowths to nucleate on sulfides.

^1,2,3Zhan Zhou,¹Jiawei Zhao,^1,4Long Xiao,^1,5Jiahuai Sun
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116205]
¹State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
²Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
³University of Chinese Academy of Sciences, Beijing 100049, China
⁴State Key Laboratory of Lunar and Planetary Sciences, Space Science Institute, Macau University of Science and Technology, Macau, China
⁵CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
Copyright Elsevier

High-pressure minerals formed during asteroid impact events are critical for unraveling the details of impact processes. Reidite, a high-pressure polymorph of zircon (ZiSiO₄), forms at ~20–50 GPa in shock-recovery experiments. However, high-contents of reidite in natural zircon (30–100%), which indicate a exceeding 40 GPa formation pressure, are rare in terrestrial and extraterrestrial materials. It is potentially associated with the extreme formation conditions, limiting the potential to use a shock thermobarometer in zircon. Here we report one outcrop of typical microstructures (reidite, granular zircon, and zirconia) in shocked zircon extracted from the outer suevite at the Ries impact crater, Germany. We describe a variety of complex habits of reidite with different proportions (0 − ~90%) of shocked zircon. As supported by previous shock-recovery experiments, these habits of reidite indicate a formation pressure of ~20–50 GPa, further constraining the application range of shock thermobarometer in natural zircon. The presence of diverse ZrSiO₄ phases at the centimeter or micrometer scale, as well as the co-occurrence of reidite, granular zircon, and zirconia at the grain scale reveal highly heterogeneous P-T conditions in outer suevite. We suggest that these thoroughly mixed materials have two types of origins: (1) The excavation flow (or cross-flow) fields mix materials with different shock levels from various positions within the crater. (2) The heterogeneous heating of impact melt result in the diversification of high-temperature phases in zircon. Furthermore, the extensive preservation of shock features of zircon such as reidite reveals that the outer suevite experienced rapid cooling during emplacement and was not exposed to a long-term overheated environment. This supports the radial flow hypothesis of emplacement rather than the FCI (fuel-coolant interaction) model. In general, this study indicates that zircon is a robust shock thermobarometer (0 − ~50 GPa) to help in understanding the formation history of parent rocks and unraveling the P-T conditions of the impact events.

^1,2Mutsumi Komatsu et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14234]
¹Division of Liberal Arts and Sciences, Saitama Prefectural University, Koshigaya, Saitama, Japan
²Department of Earth Sciences, Waseda University, Shinjuku, Tokyo, Japan
Published by arrangement with John Wiley & Sons

We present here an investigation of Ryugu particles recovered by the Hayabusa2 space mission and their extracted carbonaceous acid residues using Raman spectroscopy. Raman parameters of Ryugu intact grains and their acid residues are characterized by broad D (defect induced) and G (graphite) band widths, indicating the presence of polyaromatic carbonaceous matter with low thermal maturity. Raman spectra of Ryugu particles and CI (type 1) chondrites exhibit stronger laser-induced fluorescence backgrounds compared to Type 2 and Type 3 carbonaceous chondrites. The high fluorescence signatures and wide bandwidths of the D and G bands of Ryugu intact grains are similar to the Raman spectra observed in CI chondrites, reflecting the low structural order of their aromatic carbonaceous matter, and strengthening the link between Ryugu particles and CI chondrites. The high fluorescence background intensity of the Ryugu particles is due to multiple causes, but it is likely that the relative abundance of geometry-bearing macromolecular organic matter in total organic carbon contents makes a large contribution to the fluorescence intensities. Locally observed high fluorescence in the acid-extracted residues of Ryugu is due to nitrogen-bearing outlier phase. The high fluorescence signature is one consequence of the low degree of thermal maturity of the organic matter and supports evidence that the Ryugu particles have escaped significant parent body thermal metamorphism.

^1,2Thomas Kohout et al. (>10)
The Planetary Science Journal 5, 128 Open Access Link to Article [DOI 10.3847/PSJ/ad4266]
¹Department of Geosciences and Geography, University of Helsinki, Finland; tomas.kohout@helsinki.fi
²Institute of Geology of the Czech Academy of Sciences, Czech Republic

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Andy J. López-Oquendo,^1,2Mark J. Loeffler,¹David E. Trilling
Planetary Science Journal 5, 117 Open Access Link to Article [DOI 10.3847/PSJ/ad4028]
¹Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ 86011, USA; al2987@nau.edu
²Center for Material Interfaces in Research and Applications, Northern Arizona University, Flagstaff, AZ 86011, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹K.Yumoto et al. (>10)
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116204]
¹Department of Earth and Planetary Science, The University of Tokyo, Bunkyo, Tokyo, Japan
Copyright Elsevier

Various natural effects gradually alter the surfaces of asteroids exposed to the space environment. These processes are collectively known as space weathering. The influence of space weathering on the observed spectra of C-complex asteroids remains uncertain. This has long hindered our understanding of their composition and evolution through ground-based telescope observations. Proximity observations of (162173) Ryugu by the telescopic Optical Navigation Camera (ONC-T) onboard Hayabusa2 and that of (101955) Bennu by MapCam onboard Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) found opposite spectral trends of space weathering; Ryugu darkened and reddened while Bennu brightened and blued. How the space weathering trends on Ryugu and Bennu evolved relative to each other would place an important constraint for understanding their mutual relationship and differences in their origins and evolutions. In this study, we compared the space weathering trends on Ryugu and Bennu by applying the results of cross calibration between ONC-T and MapCam obtained in our companion paper. We show that the average Bennu surface is brighter by 18.0 ± 1.5% at v band (550 nm) and bluer by 0.18 ± 0.03 (μm−1; in the 480–850 nm spectral slope) than Ryugu. The spectral slopes of surface materials are more uniform on Bennu than on Ryugu at spatial scales larger than ~1 m, but Bennu is more heterogeneous at scales below ~1 m. This suggests that lateral mixing due to global-scale resurfacing processes may have been more efficient on Bennu. The reflectance−spectral slope distributions of craters on Ryugu and Bennu appeared to follow two parallel trend lines with an offset before cross calibration, but they converged to a single straight trend without a bend after cross calibration. We show that the spectra of the freshest craters on Ryugu and Bennu are indistinguishable within the uncertainty of cross calibration. These results suggest that Ryugu and Bennu initially had similar spectra before space weathering and that they evolved in completely opposite directions along the same trend line, subsequently evolving into asteroids with different disk-averaged spectra. These findings further suggest that space weathering likely expanded the spectral slope variation of C-complex asteroids, implying that they may have formed from materials with more uniform spectral slopes.

¹B.G. Rider-Stokes,^1,2A. Stephant,^1,3M. Anand,¹I.A. Franchi,¹X. Zhao,¹L.F. White⁴A. Yamaguchi,¹R.C. Greenwood,¹S.L. Jackson
Earth and Planetary Science Letters 642, 118860 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2024.118860]
¹School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
²Istituto di Astrofisica e Planetologia Spaziali – INAF 00111 Rome, Italy
³Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK
⁴National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
Copyright Elsevier

The quenched (rapidly-cooled) angrite meteorites, which formed in the inner Solar System, record large-scale planetary mixing in the first few Ma of Solar System history, and therefore, provide a unique opportunity to investigate the role of impacts in terms of water addition to the growing planetesimals. Here we investigate the H isotopic composition and H2O abundance of relict olivine grains that survived impact melting within Asuka (A) 12,209 and compare them with impact melt-produced groundmass fractions using in-situ nanoscale secondary ion mass spectrometry (NanoSIMS). These analyses test if the angrite parent body (APB) acquired a CC-like H isotopic composition before early large-scale impact mixing and/or acquired volatiles by subsequent impact(s). Furthermore, we analyse the H isotopic composition and H2O abundance of later-forming plutonic (NWA 4801), intermediate (NWA 10,463) and dunitic (NWA 8535) angrite meteorites to assess the role of impacts, in terms of volatile delivery, during the first 50 Ma of the inner Solar System history. The H isotopic composition of most quenched angrites appears to be affected by degassing. Consequently, we opt to use the weighted average δD of pyroxenes and olivines in the plutonic angrite, NWA 4801, to estimate the original composition of the APB (-235 ± 113 ‰ 1σ, n = 18), in agreement with recent studies on the hydrogen isotopic signatures of mineral-hosted melt inclusions in D’Orbigny and Sahara 99,555. Additionally, we use the H2O abundances of NWA 4801 pyroxene (7.9 ± 1 µg/g 2σ) and olivine (6.1 ± 0.6 µg/g 2σ) to estimate the lower (85 to 110 µg/g) and upper (519 to 1089 µg/g) limits of the primitive APB mantle H2O content, implying that the APB was one of the most hydrated bodies in the early inner Solar System. The similarity of δD/H2O systematics in the relict olivine grains and groundmass olivine within A 12,209 argues against water delivery through impacts in the early inner Solar System. Overall, the non-carbonaceous reservoir in the inner Solar System appears to retain a single source of water, which isotopically resembles either water ice in carbonaceous chondrite parent bodies or fractionated nebula water.