¹M. V., ²G. Varga, Z. Dankházi,¹A. V. Chukin,³I. Felner,²E. Kuzmann,¹V. I. Grokhovsky,²Z. Homonnay,¹M. I. Oshtrakh
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14070]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russian Federation
²Department of Materials Physics, Eötvös Loránd University, Budapest, Hungary
³Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
⁴Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
Published by arrangement with John Wiley & Sons

A fragment of Mundrabilla IAB-ung iron meteorite was analyzed using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. The polished section of meteorite fragment characterization by optical microscopy and SEM shows the presence of the γ-Fe(Ni, Co) phase lamellae, plessite structures and schreibersite inclusions in the α-Fe(Ni, Co) phase. EDS indicates variations in the Ni concentrations in the following ranges: (i) ∼6.3–6.5 atom% in the α-Fe(Ni, Co) phase and (ii) ∼22 to ∼45 atom% in the γ-Fe(Ni, Co) phase lamellae including the range of ∼29–33 atom% of Ni leading to the paramagnetic state of the γ-Fe(Ni, Co) phase. Schreibersite inclusions contain ∼23 atom% of P, ∼33 atom% of Fe, ∼43 atom% of Ni, and ∼0.7 atom% of Co. Plessite structure contains the average Ni concentration of ∼17 atom% while detailed EDS analysis shows: (i) the lowest Ni concentrations of ∼5 to ∼8 atom%, (ii) the intermediate Ni concentrations of ∼9 to ∼19 atom%, and (iii) the highest Ni concentration up ∼38 atom% (some individual micro-grains demonstrate up to ∼47 and ∼59 atom% of Ni) that may indicate the presence of the (i) α-Fe(Ni, Co), (ii) α₂-Fe(Ni, Co), and (iii) γ-Fe(Ni, Co) phases. These may be a result of the γ-phase decomposition with mechanism γ → α + α₂ + γ that indicates a slow cooling rate for Mundrabilla IAB-ung iron meteorite. The presence of ∼98.6 wt% of the α-Fe(Ni, Co) phase and ∼1.4 wt% of the γ-Fe(Ni, Co) phase is found by XRD while schreibersite is not detected. Magnetization measurements show the saturation magnetization moment of Mundrabilla IAB-ung of 188(2) emu g⁻¹ indicating a low average Ni concentration in Fe-Ni-Co alloy. Mössbauer spectrum of the bulk Mundrabilla powder demonstrates five magnetic sextets related to the ferromagnetic α₂-Fe(Ni, Co), α-Fe(Ni, Co), and γ-Fe(Ni, Co) phases and one singlet associated with the paramagnetic γ-Fe(Ni, Co) phase, however, there are no spectral components corresponding to schreibersite. Basing on relatively larger and smaller values of the magnetic hyperfine field, two magnetic sextets associated with γ-Fe(Ni, Co) phase can be related to the disordered and more ordered γ-phases. The iron fractions in the detected phases can be roughly estimated as follows: (i) ∼17.6% in the α₂-Fe(Ni, Co) phase, (ii) ∼68.5% in the α-Fe(Ni, Co) phase, (iii) ∼11.5% in the disordered γ-Fe(Ni, Co) phase, (iv) ∼2.0% in the more ordered γ-Fe(Ni, Co) phase, and (v) ∼0.4% in the paramagnetic γ-Fe(Ni, Co) phase.

^1,2PengYue Wang,³Edward Cloutis,¹XiaoPing Zhang,^1,4Ye Su,^1,5YunZhao Wu
Meteoritics & Planetary Science(in Press) Link to Article [https://doi.org/10.1111/maps.14077]
¹State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
²Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, China
³Department of Geography, University of Winnipeg, Winnipeg, Canada
⁴Center for Excellence in Comparative Planetology, Chinese Academy of Science, Hefei, China
⁵Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, Chi
Published by arrangement with John Wiley & Sons

The impact threat of some near-Earth Asteroids (NEAs) drives our need to understand their mineral compositions. Quantitative mineral abundances based on reflectance spectroscopy are of great significance for studying the compositions of NEAs. In this study, we constrained the surface mineralogy of (99942) Apophis based on multiple diagnostic spectral parameters. The influence of non-mineral component factors (e.g., space weathering, phase angle, and surface temperature) on diagnostic spectral parameters was evaluated. We established the connection between Apophis and corresponding meteorite analog. Our results show that the abundances of olivine and pyroxene on the surface of Apophis are 53.4 ± 6 wt% and 35.6 ± 2 wt%, respectively. The 1 μm band width is basically unaffected by phase-angle changes and is less affected by temperature variations. Low temperature has more obvious effects on the 1.25/1 μm band depth ratio (BDR 1.25) based on the present data. When the phase angle ranges from 60° to 120°, the BDR 1.25 changes significantly with the increase or decrease of phase angle. In terms of spectral characteristics, the best meteorite analog of Apophis is LL chondrite, confirming earlier interpretations. Mineral analyses based on multiple diagnostic spectral parameters provide more consistent results. Knowledge of the surface compositions of Apophis can also inform optimum or possible defense strategies for it and other NEAs.

¹Juraj Tóth et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115791]
¹Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava, Mlynska dolina, Bratislava, 84248, Slovakia
Copyright : Elsevier

We provide an overview of the MetSpec project, which aims to connect meteorite ablation laboratory experiments with meteor spectral observations in the atmosphere aiming at the development of a methodology to identify incoming planetary material distribution into the Earth’s atmosphere. We have selected 28 meteorites of different types to represent known planetary material compositions coming from asteroids, Vesta, Mars and the Moon. Some samples have been tested twice which resulted in overall 31 experiments. Three distinct test campaigns were realized in 2020, 2021 and 2022 with the High Enthalpy Flow Diagnostics Group in the Plasma Wind Tunnel PWK1 where they have developed a unique testing scenario. During the last and most elaborated campaign, 16 cameras observed the artificial meteors in the laboratory. Besides videos and online live streaming, instruments included several spectrometers, and optical and imaging instruments covering UV, visible and IR spectral range. This special collection in Icarus collects the resulting output from the different instruments and results. This overview article provides an introduction and summarizes the main findings of the experimental campaigns.

¹Edward R. D. Scott,²Ian S. Sanders,³Erik Asphaug,²Emma L. Tomlinson
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14069]
¹Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, Honolulu, Hawai’i, USA
²Department of Geology, Trinity College Dublin, Dublin 2, Ireland
³Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

A unique 2 mm-wide clast of fine-grained garnet–omphacite peridotite with chondritic chemistry was reported from the CR2 chondrite Northwest Africa 801 by Hiyagon et al. (2016, Geochimica et Cosmochimica Acta, 186, 32–48). Those authors described the clast as eclogitic and inferred from its mineral compositions that the rock formed quickly, during perhaps 100–1000 years of burial, deep within a Moon-sized body at about 3 GPa (30 kbar) pressure and 1000°C. Such conditions are unprecedented among meteorites and invite scrutiny. Here, we discuss the clast and its origin. The inferred conditions appear justified, but the published idea of burial during a protoplanetary merger and, soon after, exhumation in a violent collision seems improbable and contrary to the clast’s low shock levels. We find that exhumation is better explained by pull-apart of a projectile in a low velocity hit-and-run collision. We try inconclusively to explain near-simultaneous burial and exhumation in a hit-and-run return scenario. Taking a different approach, and to conclude, we speculate that an approximately lunar-mass body was molten beneath a thin dense chondritic crust, of which fragments foundered and sank deep into the magma ocean as an ongoing process. Fragments that were changing to garnet–omphacite peridotite were exhumed when the molten body was pulled apart in a hit-and-run collision with a larger body.

¹Atsushi Takenouchi,²Akira Yamaguchi,³Takashi Mikouchi,⁴Richard Greenwood,⁵Sojiro Yamazaki
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14073]
¹The Kyoto University Museum, Kyoto University, Kyoto, Japan
²National Institute of Polar Research, Tokyo, Japan
³The University Museum, The University of Tokyo, Tokyo, Japan
⁴Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes, UK
⁵Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Asuka (A) 12325 is the first poikilitic shergottite having a depleted pattern in light rare earth elements (REE). Compared with known poikilitic shergottites, A 12325 has smaller but more abundant pyroxene oikocrysts with remarkable Fe-rich pigeonite rims, indicating that A 12325 cooled relatively faster at a shallower part of the crust. The redox condition (logfO2 = IW + 0.6-IW + 1.7) and Fe-rich chemical compositions of each mineral in A 12325 are close to enriched shergottites. The intermediate shergottites could not form by a simple mixing between parent magmas of A 12325 and enriched shergottites. Although A 12325 contains various high-pressure minerals such as majorite and ringwoodite, plagioclase is only partly maskelynitized. Therefore, the maximum shock pressure may be within 17–22 GPa. Thermal conduction and ringwoodite growth calculation around a shock vein revealed that the shock dwell time of A 12325 is at least 40 ms. The weaker shock pressure and longer shock dwell time in A 12325 may be attained by an impact event similar to those of nakhlites and Northwest Africa (NWA) 8159. Such a weak shock ejection event may be as common on Mars as a severe shock event recorded in shergottites. Alteration of sulfide observed in A 12325 may imply the presence of magmatic fluid in its reservoir on Mars. A 12325 expands a chemical variety of Martian rocks and has a unique shock history among poikilitic shergottites while A 12325 also implies that poikilitic shergottites are common rocks on Mars regardless of their sources.

¹Heng-Ci Tian,¹Wei Yang,¹Di Zhang,^1,3Huijuan Zhang,²Lihui Jia,²Shitou Wu,¹Yangting Lin,²Xianhua Li,²Fuyuan Wu
American Mineralogist 108, 1669-1677 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1669.pdf]
¹Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
³School of Earth Sciences, East China University of Technology, Nanchang 330013, Jiangxi, China
Copyright: The Mineralogical Society of America

This study focuses on using the chemical compositions of plagioclase to further investigate the
petrogenesis of Chang’E-5 young mare basalts and constrain its parental melt composition. Together
with previously published data, our results show that the plagioclase in mare basalts overall displays
large variations in major and trace element concentrations. Inversion of the plagioclase data indicates
that the melt compositions parental to Chang’E-5 basalts have high rare earth elements (REE) concentrations similar to the high-K KREEP rocks (potassium, rare earth elements, and phosphorus). Such a signature is unlikely to result from the assimilation of KREEP components, because the estimated
melt Sr shows positive correlations with other trace elements (e.g., Ba, La), which are far from the
KREEP end-member. Instead, the nearly parallel REE distributions and a high degree of trace element
enrichment in plagioclase indicate an extensive fractional crystallization process. Furthermore, the
estimated melt REE concentrations from plagioclase are slightly higher than those from clinopyroxene,
consistent with its relatively later crystallization. Using the Ti partition coefficient between plagioclase
and melt, we estimated the parental melt TiO2 content from the earliest crystallized plagioclase to be
~3.3 ± 0.4 wt%, thus providing robust evidence for a low-Ti and non-KREEP origin for the Chang’E-5
young basalts in the Procellarum KREEP terrane.

^1,2Xiaojing Lai,³Feng Zhu,²Dongzhou Zhang,⁴Sergey Tkachev,⁴Vitali B. Prakapenka,²Keng-Hsien Chao,²Bin Chen
American Mineralogist 108, 1530-1537 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1530.pdf]
¹Gemmological Institute, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei, 430074, China 
²Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawaii 96822, U.S.A. 
³School of Earth Sciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, Hubei, 430074, China 
⁴Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, U.S.A.
Copyright: The Mineralogical Society of America

Ice-VII is a high-pressure polymorph of H2O ice and an important mineral widely present in many
planetary environments, such as in the interiors of large icy planetary bodies, within some cold subducted
slabs, and in diamonds of deep origin as mineral inclusions. However, its stability at high pressures
and high temperatures and thermoelastic properties are still under debate. In this study, we synthesized
ice-VII single crystals in externally heated diamond-anvil cells and conducted single-crystal X-ray
diffraction experiments up to 78 GPa and 1000 K to revisit the high-pressure and high-temperature
phase stability and thermoelastic properties of ice-VII. No obvious unit-cell volume discontinuity or
strain anomaly of the high-pressure ice was observed up to the highest achieved pressures and temperatures. The volume-pressure-temperature data were fitted to a high-temperature Birch-Murnaghan
equation of state formalism, yielding bulk modulus KT0 = 21.0(4) GPa, its first pressure derivative KT′0
= 4.45(6), dK/dT = –0.009(4) GPa/K, and thermal expansion relation αT = 15(5) × 10–5 + 15(8) × 10–8
× (T – 300) K–1. The determined phase stability and thermoelastic properties of ice-VII can be used to
model the inner structure of icy cosmic bodies. Combined with the thermoelastic properties of diamonds,
we can reconstruct the isomeke P-T paths of ice-VII inclusions in diamond from depth, offering clues
on the water-rich regions in Earth’s deep mantle and the formation environments of those diamonds.

¹Lang Zhang,^1,2Ai-Cheng Zhang,¹Shu-Zhou Wang
American Mineralogist 108, 1597-1611 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1597.pdf]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China 2
²CAS Center for Excellence in Comparative Planetology, China
Copyright: The Mineralogical Society of America

Apatite is an important petrogenetic indicator in extraterrestrial materials. Here, we report the
mineralogical features of apatite and associated phases in three brachinites Northwest Africa (NWA)
4969, NWA 10637, and NWA 11756. Two types of apatite are observed: intergranular apatite and apatite
inclusion within chromite and silicate minerals. The intergranular chlorapatite is enclosed by or penetrated by irregular porous merrillite, indicating chlorapatite replacement by merrillite. The intergranular
chlorapatite is closely associated with a fine-grained pyroxene-troilite intergrowth along olivine grain
boundaries, which is a sulfidization product of olivine. High-Ca pyroxene is observed as a constituent
phase in the intergrowth for the first time. The apatite inclusions are either monomineralic or closely
associated with subhedral-euhedral pore-free merrillite. In NWA 4969, the apatite inclusions show a
large compositional variation from chlorapatite to fluorapatite and are systematically more F-rich than
intergranular apatite; while the apatite inclusions in NWA 10637 and NWA 11756 are chlorapatite. Most
of the two apatite types in brachinites contain oriented tiny or acicular chromite grains, suggesting the
exsolution of chromite from apatite. We propose that apatite replacement by merrillite, formation of
pyroxene-troilite intergrowth, and exsolution of chromite in apatite were caused by a shock-induced,
transient heating event (~930–1000 °C) on the brachinite parent body. This heating event resulted in
halogen devolatilization during replacement of the intergranular apatite by merrillite, which probably
disturbed the Mn-Cr isotopic system in brachinites as well. We also propose that the apatite inclusions
could be a residual precursor material of the brachinites.

¹Ian Szumila,¹Dustin Trail,²Timmons Erickson,³Justin I. Simon,⁴Matthew M. Wielicki,⁵Tom Lapen,¹Miki Nakajima,³Marc Fries,⁶Elizabeth A. Bell
American Mineralogist 108, 1516-1529 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1516.pdf]
¹Univesity of Rochester, Earth and Environmental Science, Rochester, New York 14611, U.S.A.
²Jacobs – JETS, NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
³Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
⁴University of Alabama, Department of Geological Sciences, Tuscaloosa, Alabama 35487, U.S.A.
⁵University of Houston, Department of Earth and Atmospheric Sciences, Houston, Texas 77004, U.S.A.
⁶University of California Los Angeles, Department of Earth, Planetary and Space Sciences, Los Angeles, California 90095, U.S.A.
Copyright: The Mineralogical Society of America

Impact events modify and leave behind a complex history of rock metamorphism on terrestrial
planets. Evidence for an impact event may be recorded in physical changes to minerals, such as mineral
deformation and formation of high P-T polymorphs, but also in the form of chemical fingerprints,
such as enhanced elemental diffusion and isotopic mixing. Here we explore laboratory shock-induced
physical and chemical changes to zircon and feldspar, the former of which is of interest because its trace
elements abundances and isotope ratios are used extensively in geochemistry and geochronology. To
this end, a granular mixture of Bishop Tuff sanidine and Kuehl Lake zircon, both with well characterized Pb isotope compositions, was prepared and then shocked via a flat plate accelerator. The peak
pressure of the experiment, as calculated by the impedance matching method, was ~24 GPa although a
broader range of P-T conditions is anticipated due to starting sample porosity. Unshocked and shocked
materials were characterized via scanning electron microscopy (SEM), electron backscatter diffraction
(EBSD), and Raman spectroscopy. These methods show that the starting zircon material had abundant
metamict regions, and the conversion of the feldspar to glass in the post-shock material. Analyses of
the shocked product also yielded multiple occurrences of the high-pressure ZrSiO4 polymorph reidite,
with some domains up to 300 μm across. The possibility of U-Pb system disturbance was evaluated
via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ion
mass spectrometry (SIMS). The isotopic data reveal that disturbance of the U-Pb geochronometer
in the reidite was minimal (<2% for the main U-Pb geochronometers). To better constrain the P-T conditions during the shock experiment, we complement impedance matching pressure calculations with iSALE2D impact simulations. The simulated results yield a range of P-T conditions experienced during the experiment and show that much of the sample may have reached >30 GPa, which
is consistent with formation of reidite. In the recovered shocked material, we identified lamellae of
reidite, some of which interlock with zircon lamellae. Reidite {112} twins were identified, which we
interpret to have formed to reduce stress between the crystal structure of the host zircon and reidite.
These two findings support the interpretation that shear transformation enabled the transition of zircon
to reidite. The size and presence of reidite found here indicate that this phase is probably common in
impact-shocked crustal rocks that experienced ~25 to ~35 GPa, especially when the target material
has porosity. Additionally, shock loading of the zircon and transformation to reidite at these pressures
in porous materials is unlikely to significantly disturb the U-Pb system in zircon and that the reidite
inherits the primary U and Pb elemental and isotopic ratios from the zircon.

¹Mark R. Boyd,¹Julia A. Cartwright,²Jaspreet Singh,²Paul A.J. Bagot,^3,4Charlotte L. Bays,³Queenie H.S. Chan,^3,5Matthew J. Genge,²Michael P. Moody
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.08.023]
¹Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
²Department of Materials, University of Oxford, Oxford, OX1 3PH, UK
³Planetary Materials Group, Natural History Museum London, SW7 5BD, UK
⁴Department of Earth Sciences, Royal Holloway, University of London, Egham, TW20 0EX, UK
⁵Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, UK
Copyright Elsevier

Micrometeorites (MMs) recovered from the Earth’s surface may have undergone significant changes prior to their collection, including weathering while residing in the terrestrial environment. These alteration processes, such as the precipitation of hydrous phases, may overprint both primary and atmospheric entry features, obscuring pre-existing material properties. In addition, weathering exerts a prominent control on the geochemical interactions, such as species mobility, between extraterrestrial material and the terrestrial environment, particularly in Antarctica. In this study, we have characterised the textural and compositional consequences of weathering on an unmelted, fine-grained, Antarctic MM, which includes the mapping of nanometre-scale features using atom probe tomography. In particular, we investigate geochemical behaviour across textural boundaries in the MM and observe nanoscale elemental heterogeneity within complex alteration assemblages. In one sample region, a compositional boundary is highlighted by distinct elemental differences, consistent with a weathering encrustation of mixed mineralogies, while analyses in other targeted regions show evidence for nanoscale elemental networks, as well as a grain boundary adjacent to a carbon-rich region. We discuss our findings in the context of terrestrial weathering as a dominant cause for the nanoscale features observed. Weathering processes responsible for these features include the leaching of extraterrestrial material, precipitation of secondary alteration products with associated layering, and the influence of mechanical stress on pre-existing weaknesses. From these results, we derive a weathering sequence to explain the formation of the alteration product assemblage and highlight the controls on MM geochemistry in the terrestrial environment. Our observations show that nanoscale carbonaceous material may be preserved in oxy-hydroxides under icy conditions, which can also act as tracers for local environmental changes.