¹Nancy L. Chabot,^1,2Colin D. Hamill,¹Evangela E. Shread,³Richard D. Ash,⁴Catherine M. Corrigan
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14341]
¹Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
²American Astronomical Society, Washington, DC, USA
³Department of Geology, University of Maryland, College Park, Maryland, USA
⁴Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
Published by arrangement with John Wiley & Sons

Troilite is a common phase in iron meteorites, but there are limited data available for the partitioning behavior of elements between troilite and solid metal. In this study, we present the results of experiments with coexisting Fe-Ni solid metal, an S-rich metallic liquid, and troilite, conducted at 800–925°C in evacuated silica tubes at 1 atm. We report solid metal–troilite partition coefficients for 22 elements commonly studied in iron meteorites. We find that elements with chalcophile behavior have an affinity for troilite and that the majority of siderophile elements are incompatible in troilite. A notable exception to this generalization is for the siderophile element Mo, which partitions roughly equally between solid metal and troilite. We find that Ni and Co are largely concentrated in the solid metal, but given their higher concentrations in iron meteorites, their partitioning behavior indicates that measurable amounts of Ni and Co should be present in iron meteorite troilite when it forms. Our work motivates the need for additional measurements of the trace element composition of iron meteorite troilite and validates the assumption made in iron meteorite crystallization models that partitioning into troilite can be neglected for the majority of siderophile elements, with the exception of Mo.

^1,2,3Denton S. Ebel,^1,4Marina E. Gemma,^1,3,5Michael K. Weisberg,^1,6Jon M. Friedrich
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14328]
¹Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
²Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
³Department of Earth and Environmental Sciences, Graduate Center of the City University of New York, New York, New York, USA
⁴Department of Geosciences, Stony Brook University, Stony Brook, New York, US
⁵Department of Physical Sciences, Kingsborough College, City University of New York, Brooklyn, New York, USA
⁶Department of Chemistry, Fordham University, Bronx, New York, USA
Published by arrangement with John Wiley & Sons

Compared to the carbonaceous chondrites (CCs), ordinary chondrites (OCs) are depleted in Mg and refractory lithophile elements. The OCs are classified by a trend from high metal (H) to low total iron (L) to low total iron and low metal (LL) compositions with increasing heavy O isotopes and refractory siderophile enrichment. We surveyed many CC for primitive materials that might be analogs of components that formed in, and then escaped, originally solar composition reservoirs from which OCs formed. Amoeboid olivine aggregates (AOA) are nodular accretions with discrete refractory Ca-, Al-, Ti-rich mineral assemblages and often with separate Fe-metal alloy nodules, all surrounded by 16O-rich, near-pure olivine Mg2SiO4 rinds. Most AOAs contain the daughter products of extinct 26Al revealing their very early ages. We find relatively large metal grains with olivine rims forming isolated or clumped nodules or “metal–olivine inclusions” in AOAs in many carbonaceous chondrites, particularly the highly primitive CO-like chondrite Acfer 094 (C2 ungr). Similar nodules have been reported in samples returned from the highly altered, CI-like asteroid Bennu by the OSIRIS-REx mission. In discrete regions and times in the protoplanetary disk, differing drift velocities of these 10s of micron scale components could have caused the correlated loss of both refractory siderophiles (in metal), refractory lithophiles, and Mg and 16O (in olivine). Varying degrees of loss of nodules similar to these “MOI,” from the chondrule-forming reservoirs from which H, L, and LL chondrites accreted could, simultaneously, explain the multiple aspects of their chemical compositions.

^1,2Wenqing Chang, ^1,2Zhiguo Meng, ²Yi Xu, ²Xiaoping Zhang, ²Roberto Bugiolacchi, ^2,3Long Xiao, ^4,5Jinsong Ping, ⁴Hongbo Zhang, ^4,5Yuanzhi Zhang
Earth and Planetary Science Letters 658, 119326 Link to Article [https://doi.org/10.1016/j.epsl.2025.119326]

¹College of Geoexploration Science and Technology, Jilin University, No.6 Ximinzhu Street, Changchun 130026, China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau 999078, China
³Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
⁴Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, CAS, Beijing 100101, China
⁵School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier

The Apollo basin, situated on the northeastern edge of the South Pole-Aitken (SPA) basin, is the sampling area for the Chang’e -6 (CE-6) mission. In this study, we investigated the microwave thermophysical properties of surface deposits in the region by comparing brightness temperature (TB) and TB difference (dTB) maps derived from CE-2 Microwave Radiometer data combined with topography, chemical elements, and Moon Mineralogy Mapper products. The main results are as follows. (1) High dTB anomaly: A significant high dTB anomaly is identified near the CE-6 landing region, characterized by the highest FeO and TiO2 contents estimated from the small-fresh craters; (2) Basaltic Volcanism: High dTB anomaly is proposed as a new basaltic unit in late stage of mare infill, and, by combining derived ages and geomorphology, we provide a new perspective on the basaltic volcanism with four episodes of magma infill in the CE-6 landing region; (3) Thermophysical Parameters: The high dTB anomaly indicates the potential importance of analyzing the returned CE-6 samples to enhance our understanding of the Moon’s surface deposits using the passive microwave remote sensing data.

¹Cody Schultz,¹Ralph E. Milliken,¹Joseph Boesenberg,^2,3Imene Kerraouch
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14339]
¹Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, Rhode Island, USA
²BCMS, Arizona State University, Tempe, Arizona, USA
³Institute für Planetologie, University of Münster, Münster, Germany
Published by arrangement with John Wiley & Sons

CM carbonaceous chondrites are complex brecciated meteorites that exhibit significant chemical, mineralogic, and petrographic diversity both between and within individual samples. As most reflectance spectroscopy studies of carbonaceous chondrites are performed on bulk powders, important questions remain about the true spectral diversity of these complex breccias and the degree to which lab-based meteorite spectra can be reliably related to remotely acquired spectra of primitive asteroids. The Aguas Zarcas meteorite is a unique CM chondrite in that it has been found to exhibit at least five chemically and isotopically distinct lithologies that are all associated with a single fall event. Here, we describe a coordinated petrographic and spectroscopic study to further investigate the thermochemical and collisional history of the Aguas Zarcas parent body and to better understand how to interpret remotely acquired spectra of primitive asteroids. Four intact sections of the Aguas Zarcas meteorite, which together represent at least three to four distinct lithologies, were analyzed using microscope FT-IR (μFT-IR) spectroscopy and electron probe microanalysis (EPMA) elemental mapping. Our study found significant variations in spectral features, particularly in the mid-infrared (MIR) wavelength region, that can be linked to petrographic diversity between lithologies. The relative abundance of matrix phyllosilicates and pyroxene appears to have the strongest influence on the shape, position, and strength of MIR spectral features. Linear spectral unmixing models as a method for compositional interpretation showed varying accuracy when compared to EPMA-based estimates, with integrated μFT-IR spectral maps showing better results compared to unmixing of bulk (larger spot size) FT-IR spectra. A notable discovery in two sections of the Aguas Zarcas meteorite was the presence of carbonate veins along the boundary of chemically and petrographically separate lithologies, which provide important constraints on the nature and timing of pre- and post-brecciation aqueous alteration.

^1,2Fridolin Spitzer, ^1,2Christoph Burkhardt, ³Thomas S. Kruijer, ^1,2Thorsten Kleine
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.03.021]
¹Max Planck Institute for Solar System Research, Department for Planetary Sciences, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue (L-231), Livermore, CA 94550, USA
Copyright Elsevier

Isotope anomalies in meteorites reveal a fundamental dichotomy between Non-Carbonaceous- (NC) and Carbonaceous-type (CC) planetary bodies. Until now, this dichotomy is established for the major meteorite groups, representing about 36 distinct parent bodies. Ungrouped meteorites represent an even larger number of additional parent bodies, but whether they conform to the overall NC-CC dichotomy is unknown. Here, the genetics and chronology of 26 ungrouped iron meteorites is considered through nucleosynthetic Mo and radiogenic W isotopic compositions. Secondary cosmic ray-induced modifications of these isotope compositions are corrected using Pt isotope measurements on the same samples. We find that all of the ungrouped irons have Mo isotope anomalies within the range of the major meteorite groups and confirm the NC-CC dichotomy for Mo, where NC and CC meteorites define two distinct, subparallel s-process mixing lines. All ungrouped NC irons fall on the NC-line, which is now precisely defined for 41 distinct parent bodies. The ungrouped CC irons show scatter around the CC-line indicative of small r-process Mo heterogeneities among these samples. These r-process Mo isotope variations correlate with O isotope anomalies, most likely reflecting mixing of CI chondrite-like matrix, chondrule precursors and Ca-Al-rich inclusions. This implies that CC iron meteorite parent bodies accreted the same nebular components as the later-formed carbonaceous chondrites. The Hf-W model ages of core formation for the ungrouped irons overlap with those of the iron meteorite groups from each reservoir and reveal a narrow age peak at ∼3.3 Ma after Ca-Al-rich inclusions for the CC irons. By contrast, the NC irons display more variable ages, including younger ages indicative of impact-induced melting events, which seem absent among the CC irons. This is attributed to the more fragile and porous nature of the CC bodies, making impact-induced melting on their surfaces difficult. The chemical characteristics of all iron meteorites together reveal slightly more oxidizing conditions during core formation for CC compared to NC irons. More strikingly, strong depletions in moderately volatile elements, typical of many iron meteorite parent bodies, predominantly occur among CC irons, for reasons that remain unclear at present.

¹Kirsten Larsen,^1,Alexander N. Krot,¹Daniel Wielandt,²Kazuhide Nagashima,³Guy Libourel,^1,2Martin Bizzarro
Meteoritics & Planetary Society (in Press) Link to Article [https://doi.org/10.1111/maps.14325]
¹Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark
²Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawaii, USA
³Observatoire de la Côte d’Azur, UMR 7293 LAGRANGE, Nice, France
Published by arrangement with John Wiley & Sons

A coarse-grained igneous calcium-aluminum-rich inclusion (CAI) N-53, 4.3 × 5.9 mm in size, from the CR (Renazzo-type) carbonaceous chondrite Northwest Africa (NWA) 6043 is composed of two mineralogically, chemically, and isotopically distinct units—type B (B) and type C (C). Type B unit occurs in the CAI core and consists of melilite (Åk28–56), AlTi-diopside, anorthite, spinel, and minor Fe,Ni-metal. Type C unit forms islands in B (Cc) and mantle (Cm) around it and consists of Na-bearing åkermanitic melilite (Åk58–72, 0.18–0.86 wt% Na2O), anorthite, AlTi-diopside (up to 1.2 wt% Cr2O3), spinel (up to 2.1 wt% Cr2O3), perovskite, and minor wollastonite. The outermost portion of N-53 contains relict grains of olivine (Fa4) and low-Ca pyroxene (Fs4Wo5); Wark–Lovering rim is absent. Magnesian spinel in B and C is 16O-rich (Δ17O ~ −23‰); Cr-bearing spinel in Cm is 16O-depleted (Δ17O ~ −11‰). AlTi-diopside, anorthite, and melilite in B and Cc are 16O-depleted to various degrees (Δ17O ~ −22‰ to −19‰, −21‰ to −17‰, −13‰ to −8‰, respectively). AlTi-diopside, anorthite, and melilite in Cm show a range of compositions correlated with a distance from the CAI edge (Δ17O ~ −18‰ to −8‰, −16‰ to −8‰, ~ −8‰ to −2‰). Melilite in B has the heaviest Mg-isotope composition (Δ25Mg ~ 10‰); average Δ25Mg of melilite, AlTi-diopside, and spinel in C are ~9, ~8‰, and ~6‰, respectively; anorthite in both units has Δ25Mg of ~4‰. On the Al-Mg evolutionary diagram, melilite data in B oscillate around the canonical isochron. Melilite, AlTi-diopside, and spinel in C have resolvable δ26Mg* and deviate to the left of this isochron; anorthite in both units has barely resolvable δ26Mg*. Although these data are consistent with late-stage reprocessing of N-53, they provide no clear chronological information. We conclude that N-53 experienced multiple melting events. Initial melting of solid precursors took place in an 16O-rich gaseous reservoir and resulted in formation of the uniformly 16O-rich (Δ17O ~ −24‰) type B CAI. Subsequent single- or multi-stage partial melting of this CAI occurred in an 16O-depleted gaseous reservoir(s) and resulted in addition of SiO and Na to the CAI melt, O- and Mg-isotope exchange, and crystallization of C unit.

^1,2,3Harold C. Connolly Jr et al. (>10)
Meteoritics & Planetary Society (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14335]
¹Department of Geology, School of Earth and Environment, Rowan University, Glassboro, New Jersey, USA
²Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
³Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
Published by arrangement with John Wiley & Sons

The OSIRIS-REx mission returned a sample of regolith from the carbonaceous asteroid Bennu in September 2023. We present preliminary in situ investigations of the petrology and petrography of selected particles ranging in size from 0.5 to 3 mm. Using a combination of optical and electron beam techniques, we investigate whole specimens and polished sections belonging to morphologically and visually distinct categories of particles. We find that morphological differences in the particles are reflective of petrographic and petrologic differences, leading to the conclusion that we have at least two distinct major lithologies in the bulk sample. Our findings support predictions from remote sensing, suggesting that the morphological differences observed in the boulder population of Bennu correspond to petrologic differences. Our data provide insight into the geologic activity on Bennu’s parent body and the petrographic framework needed to contextualize the detailed analyses of this pristine asteroidal material.

¹Satoru Yamamoto,¹Moe Matsuoka,²Hiroshi Nagaoka,³Makiko Ohtake,¹Ayame Ikeda
Journal of Geophysical Research (Planets) (in Press) Link to Artice [https://doi.org/10.1029/2024JE008663]
¹Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
²Earth and Space Exploration Center, Ritsumeikan University, Kusatsu Shiga, Japan
³School of Computer Science and Engineering, The University of Aizu, Aizuwakamatsu, Japan
Published by arrangement with John Wiley & Sons

We studied the global distribution and geological features of lunar surface sites whose spectra indicate an ilmenite-rich composition. Hyperspectral data obtained by the Kaguya Spectral Profiler were used for data mining to identify diagnostic features of a 1- and 2-μ
m spectral reflectance of ilmenite, revealing the global distribution of sites showing ilmenite-rich spectra. The results show that regions with ilmenite-rich spectra are concentrated at the margins of impact basins on the lunar nearside, whereas no such regions are identified in the Feldspathic Highland Terrain or the South Pole-Aitken basin. Using multiband images and a digital terrain model obtained by the Kaguya Multiband Imager and Terrain Camera, we examined the geological features of each site showing ilmenite-rich spectra and found that most of the sites are distributed on pyroclastic deposits overlying highland materials. Spectra interpreted as glass-rich material are prevalent in and around areas having ilmenite-rich spectra. However, sites showing ilmenite-rich spectra do not correspond to mare regions with
-rich basalts. These results may indicate that the concentration of ilmenite in pyroclastic deposits is high enough to exhibit diagnostic features of 1- and 2-μ
m spectral reflectance of ilmenite, whereas the concentration in mare regions with
-rich basalt is not. Since pyroclastic deposits are expected to be extensive, deep unconsolidated deposits of relatively block-free debris, resulting in high processing efficiency in the hydrogen reduction processes, our data may be useful for developing an efficient exploration strategy for ilmenite as a lunar resource.

^1,2Huanyu Wu,^1,2Yuan Zou,³Chi Zhang,³Wei Yang,^2,4Bo Wu,^2,5Kai-Leung Yung,^1,2Qi Zhao
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008787]
¹Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China
²Research Centre for Deep Space Explorations, The Hong Kong Polytechnic University, Hong Kong, China
³Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
⁴Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong, China
⁵Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China
Published by arrangement with John Wiley & Sons

Chang’e-5 (CE-5) lunar regolith samples were scanned using X-ray micro-computed tomography (micro-CT), and over 0.7 million particles were extracted from the images through machine learning-based segmentation. This is the largest three-dimensional (3D) image data set on lunar regolith particles to date, offering a unique opportunity to study the key characteristics of the lunar regolith. The image intensity was correlated with mineral density, allowing for the assessment of the bulk density (1.58 g/cm3), true density (3.17 g/cm3), and mineralogy of the lunar regolith. Glass and plagioclase contributed 45.6 wt.% of the samples, while pyroxene and olivine made up 49.7 wt.%, and ilmenite accounted for 4.7 wt.%. The median grain size of CE-5 was 57.5 μm, smaller than the Apollo 11, 16 and Luna 16, 20 and 24 samples. Spherical harmonic (SH) analysis and aspect ratio (AR) measurement revealed that the CE-5 lunar regolith particles have more complex shapes than two common terrestrial soils and exhibit less spherical shapes than Apollo 11, 16 and Luna 16, 20 and 24 samples. We recommend using size and shape characteristics cautiously when inferring the lunar regolith maturity because the intrinsic crystal size of the protolith and complex lunar surface weathering can cause significant size and shape variations. Additionally, characterizing particle shapes requires a large sample size (>1,000) to prevent skewed results from outliers. Our non-destructive examination method offers a novel and appealing approach for analyzing critical physical, mineralogical, and morphological properties of million-scale extraterrestrial soil particles, paving the way for future deep space explorations.

^1,2Peter Jenniskens,³Hadrien A. R. Devillepoix
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14321]
¹SETI Institute, Mountain View, California, USA
²NASA Ames Research Center, Moffett Field, California, USA
³Space Science and Technology Centre and International Centre for Radio Astronomy Research, Curtin University, Perth, Western Australia, Australia
Published by arrangement with John Wiley & Sons

With the goal to determine the origin of our meteorites in the asteroid belt, video and photographic observations of meteors have now tracked 75 meteorite falls. Six years ago, there were just hints that different meteorite types arrived on different orbits, but now, the number of orbits (N) is high enough for distinct patterns to emerge. In general, 0.1–1-m sized meteoroids do not arrive on similar orbits as the larger ~1-km sized near-Earth asteroids (NEA) of corresponding taxonomic class. Unlike larger NEA, a group of H chondrite meteoroids arrived on low-inclined orbits from a source just beyond the 5:2 mean-motion resonance with Jupiter (N = 12), three of which have the 7 Ma cosmic ray exposure (CRE) age from a significant collision event among H chondrites. There is also a source of H chondrites low in the inner main belt with a ~35 Ma CRE age (N = 8). In contrast, larger H-like taxonomic S-class NEA arrive from high-inclined orbits out of the 3:1 resonance. Some H chondrites do so also, four of which have a 6 Ma CRE age and two have an 18 Ma CRE age. L chondrites arrive from a single source low in the inner main belt, mostly via the ν6 secular resonance (N = 21), not the 3:1 resonance as most L-like NEA do. LL chondrites arrive too from the inner main belt (N = 5), as do larger LL-like NEA. CM chondrites are delivered from a low i < 3° inclined source beyond the 3:1 resonance (N = 4). Source asteroid families for these meteorite types are proposed, many of which have the same CRE age as the asteroid family’s dynamical age. Also, two HED achondrites are now traced to specific impact craters on asteroid Vesta.