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.

^1,2Lisa Maria Eckart,¹Jon K. Hillier,¹Frank Postberg,³Simone Marchi,⁴Zoltan Sternovsky
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14060]
¹Freie Universität Berlin, Berlin, Germany
²ETH Zürich, Zürich, Switzerland
³Southwest Research Institute, Boulder, Colorado, USA
⁴University of Colorado Boulder, Boulder, Colorado, USA
Published by arrangement with John Wiley & Sons

Linking meteorites to their asteroid parent bodies remains an outstanding issue. Space-based dust characterization using impact ionization mass spectrometry is a proven technique for the compositional analysis of individual cosmic dust grains. Here we investigate the feasibility of determining asteroid compositions via cation mass spectrometric analyses of their dust ejecta clouds during low (7–9 km s−1) velocity spacecraft flybys. At these speeds, the dust grain mass spectra are dominated by easily ionized elements and molecular species. Using known bulk mineral volume abundances, we show that it is feasible to discriminate the common meteorite classes of carbonaceous chondrites, ordinary chondrites, and howardite–eucrite–diogenite achondrites, as well as their subtypes, relying solely on the detection of elements with ionization efficiencies of ≤700 or ≤800 kJ mol−1, applicable to low (~7 km s−1) and intermediate (~9 km s−1) flyby speed scenarios, respectively. Including the detection of water ion groups enables greater discrimination between certain meteorite types, and flyby speeds ≥10 km s−1 enhance the diagnostic capabilities of this technique still further. Although additional terrestrial calibration is required, this technique may allow more unequivocal asteroid-meteorite connections to be determined by spacecraft flybys, emphasizing the utility of dust instruments on future asteroid missions.

¹A.L. Mattioda,^1,2L. Gavilan,^1,2C.L. Ricketts,^1,3P.K. Najeeb,^1,4A. Ricca,^1,5C. Boersma
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115769]
¹NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA
²Bay Area Environmental Research Institute (BAERI), Sonoma, CA 95476, USA
³Oak Ridge Associated Universities (ORAU), Oak Ridge, TN 37830, USA
⁴SETI Institute, Carl Sagan Center, Mountain View, CA 94043, USA
⁵San Jose State University Research Foundation, San Jose, CA 95112, USA
Copyright Elsevier

The NASA Raman Spectroscopic Database (Ramdb) was developed to provide a publicly accessible, user-friendly database for spectra relevant to the planetary science community. This paper describes the first set of spectra made available in version 1.00 of Ramdb, the methods used to obtain and process the Raman spectra, and provides a walkthrough of the database website that is located at http://www.astrochemistry.org/ramdb. Ramdb presently offers 112 laboratory and theoretical Raman spectra of samples relevant to planetary exploration and space science. Laboratory spectra were measured at multiple laser excitation wavelengths, namely: 405, 532, and 785 nm. Spectral data for six projects (amino acids, polycyclic aromatic hydrocarbons, carbon allotropes, minerals, analogs, and planetary studies) are provided as both raw and processed, tagged with key spectroscopic parameters, and, where applicable, accompanied by microscope images of the samples. The contents of Ramdb will be continuously expanded with a wide range of samples relevant to Astrophysics, Planetary Science, Exobiology, and Earth Science, guided by ongoing and future space exploration missions.

¹Cyrena Anne Goodrich et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14066]
¹Lunar and Planetary Institute, USRA, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

The anomalous polymict ureilite Almahata Sitta (AhS) fell in 2008 when asteroid 2008 TC3 disintegrated over Sudan and formed a strewn field of disaggregated clasts of various ureilitic and chondritic types. We studied the petrology and oxygen isotope compositions of enstatite meteorite samples from the University of Khartoum (UoK) collection of AhS. In addition, we describe the first bona fide (3.5 mm-sized) clast of an enstatite chondrite (EC) in a typical polymict ureilite, Northwest Africa (NWA) 10657. We evaluate whether 2008 TC3 and typical polymict ureilites have a common origin, and examine implications for the history of enstatite meteorite asteroids in the solar system. Based on mineralogy, mineral compositions, and textures, the seven AhS EC clasts studied comprise one EHa3 (S151), one ELb3 (AhS 1002), two EHb4-5 (AhS 2012, AhS 26), two EHb5-6 or possibly impact melt rocks (AhS 609, AhS 41), and one ELb6-7 (AhS 17), while the EC clast in NWA 10657 is EHa3. Oxygen isotope compositions analyzed for five of these are similar to those of EC from non-UoK collections of AhS, and within the range of individual EC meteorites. There are no correlations of oxygen isotope composition with chemical group or subgroup. The EC clasts from the UoK collection show the same large range of types as those from non-UoK collections of AhS. The enstatite achondrite, AhS 60, is a unique type (not known as an individual meteorite) that has also been found among non-UoK AhS samples. EC are the most abundant non-ureilitic clasts in AhS but previously were thought to be absent in typical polymict ureilites, necessitating a distinct origin for AhS. The discovery of an EC in NWA 10657 changes this. We argue that the types of materials in AhS and typical polymict ureilites are essentially similar, indicating a common origin. We elaborate on a model in which AhS and typical polymict ureilites formed in the same regolith on a ureilitic daughter body. Most non-ureilitic clasts are remnants of impactors implanted at ~50–60 Myr after CAI. Differences in abundances can be explained by the stochastic nature of impactor addition. There is no significant difference between the chemical/petrologic types of EC in polymict ureilites and individual EC meteorites. This implies that fragments of the same populations of EC parent bodies were available as impactors at ~50–60 Myr after CAI and recently. This can be explained if materials excavated from various depths on EC bodies at ~50–60 Myr after CAI were reassembled into mixed layers, leaving relatively large bodies intact to survive 4 billion years. Polymict ureilites record a critical timestep in the collisional and dynamical evolution of the solar system, showing that asteroids that may have accreted at distant locations had migrated to within proximity of one another by 50–60 Myr after CAI, and providing constraints on the dynamical processes that could have caused such migrations.

¹Sebastián Tomás Sánchez Gómez,²Jens Ormö,³Carl Alwmark,³Sanna Holm-Alwmark,³Gabriel Zachén,⁴Robert Lilljequist,¹Juan Antonio Sánchez Garrido
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14063]
¹Departamento de Agronomía, Universidad de Almería, Almería, Spain
²Centro de Astrobiología (CAB), INTA-CSIC, Instituto Nacional de Técnica Aeroespacial-Consejo Superior de
³Investigaciones Científicas, Carretera de Ajalvir km 4, Torrejón de Ardoz, Madrid, Spain
⁴Department of Geology, Lund University, Lund, Sweden
⁵Eurogeologist, Estepona, Málaga, Spain
Published by arrangement with John Wiley & Sons

The Tabernas–Alhabia Basin is a structural depression situated in the province of Almería, southeastern Spain. The basin is filled with Neogene, Pliocene, and Pleistocene sediments resting discordantly on a Paleozoic metamorphic basement. During the marine Tortonian sedimentation, a bed of breccia (Gordo megabed) was formed. It consists of rotated sedimentary megablocks commonly capped and/or surrounded by a polymict breccia composed mainly of up to dm-sized clasts of the crystalline (schist) basement. Previous work has suggested the bed to be a seismite corresponding to events induced by earthquakes. Here, we link the formation of the Gordo megabed with an ∼5 km wide, rimmed depression with exposed breccias on the northern flank of the Sierra de Gádor mountain. This semicircular structure, developed in mainly schists and dolostone of the basement, is delimited to the W, S, and E by an up to 350 m high escarpment with overturned stratigraphy. Toward the north, this crater-like structure opens toward the Gordo megabed of the Tabernas Basin. In the southern sector, the overturned strata transform outward for into a blocky allochthonous breccia with decreasing thickness and clast size. In the interior of the structure, there are occurrences of graded breccia and arenite superposed on a blocky, autochthonous breccia. Based on the presence of mineralogical shock metamorphic evidence, potential shatter cones, and a high Ir anomaly (∼500 ppb) as well as the position of the structure near the town of Alhama de Almería, we propose to call it the Alhama de Almería impact structure.

¹Zelia Dionnet et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14068]
¹CNRS, Institut d’Astrophysique Spatiale, Université Paris-Saclay, Orsay, France
Published by arrangement with John Wiley & Sons

We report μm-scale nondestructive infrared (IR) hyperspectral results (IR computed tomography, IR-CT) in 3-D and IR surface imaging, IR-S) in 2-D, at SOLEIL) combined with X-ray nano-computed tomography analyses (at SPring-8) performed on eight small Ryugu fragments extracted from mm-sized grains coming both from touchdown first and second sites. We describe the multiscale assembly of phyllosilicates, carbonates, sulfides, oxides, and organics. Two types of silicates, as well as diverse kinds of organic matter, were detected inside Ryugu material. Their spatial correlations are described to discuss the role of the mineralogical microenvironments in the formation/evolution of organic matter. In particular, we have shown that there is a redistribution of the organic matter diffuse component during aqueous alteration on the parent body, with a preferential circulation among fine-grained phyllosilicates.

^1,2Iori Kajitani,³Mizuho Koike,⁴Ryoichi Nakada,⁵Gaku Tanabe,^2,6Tomohiro Usui,⁷Fumihiro Matsu’ura,⁸Keisuke Fukushi,⁵Tetsuya Yokoyama
Earth and Planetary Science Letters 620, 118345 Link to Article [https://doi.org/10.1016/j.epsl.2023.118345]
¹Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency. 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
³Earth and Planetary Systems Science Program, Department of Advanced Science and Engineering, Hiroshima University. 1-3-1 Kagamiyama, Higashihiroshima, Hiroshim 739-8526, Japan
⁴Kochi Institute for Core Sample Research, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC). 200 Monobe, Nankoku, Kochi 783-8502, Japan
⁵Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology. 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
⁶Earth-Life Science Institute, Tokyo Institute of Technology. 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
⁷International Center for Isotope Effects Research, Nanjing University, Nanjing, Jiangsu Province 210023, China
⁸Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Ishikawa, Japan
Copyright Elsevier

The aqueous environment and possible habitability of early Mars have been widely studied based on orbital and in situ explorations, as well as analyses of Martian meteorites. Using microscale X-ray absorption near edge structure (μ-XANES) analysis, we report the first sulfur (S) speciation of the carbonates in a Martian meteorite, Allan Hills 84001, precipitated in the 4-billion-year-old aqueous alteration on Mars. The XANES data show diagnostic signatures of oxidized sulfur in the carbonates, indicating that carbonate-associated sulfate (CAS) formed from coexisting sulfate ions (SO
) in the aqueous fluid. A thermodynamic calculation suggests that the CAS deposited from a fluid with a moderately oxidizing to reducing and neutral to slightly alkaline pH condition. The possible sources of SO
ions are the minor SOx species in the Noachian atmosphere and/or the supply from volcanic gas. It is concluded that considerable amounts of the atmospheric volatiles including CO2 and SOx may have been stored as alteration products (e.g., carbonates) in the Martian underground system.

^1,2Andrea Patzer,¹Emma S. Bullock,¹Conel M. O’D. Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.08.021]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Rd. NW, Washington D.C. 20015, USA
²Geosciences Center, University of Göttingen, Goldschmidtstr. 1, 37077 Göttingen, Germany
Copyright Elsevier

In continuation of our comprehensive study of the carbonaceous chondrites, we here present data for the CM chondrites. Our study’s aim is to determine the abundances and the average elemental compositions of the major and minor chondritic components. The overarching goal has been to explore the fundamental question of whether chondrules and matrix are complementary, i.e., genetically related, or if these major chondritic components evolved separately before accretion as in the four-component model.

Using point-counting and electron microprobe analyses, we investigated the most primitive CMs known to date: Asuka (A) 12169 (CM3.0), A 12236 (CM2.9) and Paris (CM2.7-2.9). Despite their primitiveness, however, none of the samples is completely devoid of signs of terrestrial and/or parent body alteration. For instance, we found evidence for the mobilization and heterogenous redistribution of Ca, as well as for the leaching of Al from chondrules and redeposition into matrix. There is also a trend of the Ca and Al abundances in both, chondrules and matrix, to become increasingly heterogeneous with increasing parent body alteration. We were, therefore, unable to test chondrule-matrix complementarity and the four-component model using Al and Ca. Assuming that Mg and Si are insignificantly affected by alteration and that the Mg/Si ratios of the components in A 12169 are unaltered, our data indicate the pre-accretionary loss from matrix of ∼12 wt.% forsterite (matching our results for the primitive COs and CRs) and the addition of a roughly similar amount of forsterite to the chondrules (contrary to our results for the COs and CRs). These results are inconsistent with the four-component model but, based on the matrix/chondrule abundance ratio, complementarity predicts that the addition of forsterite to chondrules should have been significantly higher. This and the possibility that A 12169 component compositions have been modified to some degree means that our results do not unambiguously favor either model.