¹Daniel O. Cukierski,¹David W. Peate,^1,2Ingrid A. Ukstins,¹Christy Kloberdanz,¹C. Tom Foster,^1,3Chungwan Lim
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14322]
¹Department of Earth & Environmental Sciences, University of Iowa, Iowa City, Iowa, USA
²School of Environment, The University of Auckland, Auckland, New Zealand
³Department of Earth Science Education, Kongju National University, Kongju, Chungnam, Republic of Korea
Published by arrangement with John Wiley & Sons

Samples of impactite from the small (~350 m diameter) Monturaqui crater in northern Chile contain Fe-Ni metallic spherules sourced from the iron meteorite impactor. Textural characterization and quantification were done using SEM and μCT data. Two textural types are distinguished, with different size distributions. The smaller spherical objects (mostly <100 μm in diameter) follow a power law size distribution, while larger objects are mostly irregular-shaped patches. These are analogous to the small (nm to 50 μm) immiscible spherical metal droplets and large (150–500 μm) irregular partly fused pieces of the iron meteorite projectile observed in highly shocked ejecta fragments during hypervelocity impact experiments. Compositions of both spherule types were determined using in situ methods (electron microprobe, LA-ICP-MS), as well as solution ICP-MS on individual spherules separated from impact melt glass using electric pulse disintegration. Spherules are enriched in Ni and Co relative to Fe and W and relative to the inferred iron meteorite impactor composition, and PGEs show similar enrichments with limited fractionation between different PGEs, all consistent with selective oxidation processes. All spherules have similar chondrite-normalized patterns that are also broadly similar to weathered fragments of the iron meteorite impactor. Ni-Ge and Ni-Ir data on large (>300 μm) spherules and weathered meteorite fragments suggest that the Monturaqui impactor was a group IAB iron meteorite.

¹Martin R. Lee,¹Cameron J. Floyd,¹Robin Haller,¹Sammy Griffin
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14310]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
Published by arrangement with John Wiley & Sons

Xenoliths in carbonaceous chondrites include lithologies that are unrepresented in the meteorite record and so are a rich source of information on asteroid diversity. Cold Bokkeveld is a CM2 regolith breccia that contains both hydrous and anhydrous lithic clasts. Here, we describe a hydrous clast with a fine-grained rim. This rim shows that the clast is a xenolith that interacted with dust in the protoplanetary disk between liberation from its protolith and incorporation into Cold Bokkeveld’s parent body. Prior to its fragmentation, the xenolith’s protolith had undergone brittle deformation, with the fractures produced being cemented by carbonates to make veins. After being incorporated into Cold Bokkeveld’s parent body, the veined xenolith experienced a second phase of aqueous alteration leading to hydration of its fine-grained rim, replacement of carbonate by tochilinite–cronstedtite intergrowths, and formation of magnetite within its fine-grained matrix. The veined xenolith’s protolith underwent its entire geological evolution (accretion–aqueous alteration–fracturing–fragmentation) before Cold Bokkeveld’s parent body had accreted. Such a short lifespan may be explained by explosive breakup of the protolith due to overpressure from gases produced internally during water–rock interaction. Early fragmentation effectively acted as a thermostat to limit runaway heating that may have otherwise resulted from the body’s high concentrations of 26Al. Many other hydrous lithic clasts in CM carbonaceous chondrite meteorites could be the remains of such ephemeral early asteroids, but they are hard to identify without evidence that they were accreted as hydrous lithologies and contemporaneously with chondrules.

¹Lulu Zhao,¹Anbei Deng; Hanlie Hong,²Jiannan Zhao,^1,3,4Thomas J. Algeo,¹Fuxing Liu,⁵Nanmujia Luozhui,¹Qian Fang
American Mineralogist 110, 217-231 Link to Article [https://doi.org/10.2138/am-2023-9299]
¹State Key Laboratory of Biogeology and Environmental Geology, Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
²Key Laboratory of Geological Survey and Evaluation of Ministry of Education, China University of Geosciences, Wuhan 430074, China
³Department of Geosciences, University of Cincinnati, Cincinnati, Ohio 45221-0013, U.S.A.
⁴State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
⁵Military-Civilian Integrated Geological Survey Center, China Geological Survey, Lhasa 850006, China
Copyright: The Mineralogical Society of America

Clay minerals are common in martian geological units and are globally widespread on Earth. Understanding the origin, formation, and alteration of clay minerals is crucial for unraveling past environmental conditions on Earth and Mars, in which the composition and crystallinity of clay minerals serve as important surrogate indicators for addressing these issues. Here, 621 soil and sediment samples from five chronosequences representing different climatic zones of China were investigated using visible to near-infrared reflectance (VNIR) in combination with X-ray diffraction (XRD) analysis. The crystallinity of clay minerals (i.e., illite crystallinity, illite chemistry index, kaolinite crystallinity) and clay mineral alteration index (CMAI) were analyzed with conventional methods and then predicted through a spectral modeling approach. Our results show that kaolinite with a pedogenic or sedimentary origin is characterized by a broad crystallinity range and a poorly ordered structure, especially when generated in an intense weathering environment. Predictive models were constructed with data-mining methods, including partial least-squares regression (PLSR), random forest (RF), and Cubist algorithms. The predictive performance of the crystallinity and CMAI proxies is robust, with an overall accuracy of 78% and a residual prediction deviation (RPD) of 2.57. We also found that the model’s accuracy in predicting clay-mineral-related proxies increased by 45% using random forest (RF) and Cubist compared to the PLSR models. We suggest that VNIR spectroscopy combined with RF and Cubist methods has the potential to be an alternative and broadly applicable tool for analyzing typical clay-mineral proxies, substituting for a series of common mineralogic analyses. Spectral modeling can reveal genetic and climatic information at both field and regional scales, which has profound implications for Mars missions and other space exploration programs.

^1,2Mélissa Martinot,¹Kerri L. Donaldson Hanna,³Benjamin T. Greenhagen,¹Luis Santori,³Patrick N. Peplowski,³Joshua T. S. Cahill
The Planetary Science Journal 6, 20 Open Access Link to Article [DOI 10.3847/PSJ/ad94f0]
¹Department of Physics, University of Central Florida, 4111 Libra Drive, Orlando, FL 32816, USA
²CRPG, CNRS/Université de Lorraine, Vandœuvre-lès-Nancy, France
³The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA

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

¹Peter Wurz,¹Noah Jäggi,¹André Galli,¹Audrey Vorburger,²Deborah Domingue,³Paul S. Szabo,⁴Johannes Benkhoff,⁵Océane Barraud,⁶Daniel Wolf Savin
The Planetary Science Journal 6, 24 Open Access Link to Article [DOI 10.3847/PSJ/ad95fa]
¹Space Science and Planetology, Physics Institute, University of Bern, Bern, Switzerland
²Planetary Science Institute, Tucson, AZ, USA
³Space Sciences Laboratory, University of California, Berkeley, CA, USA
⁴ESA/ESTEC, Noordwijk, The Netherlands
⁵German Aerospace Center (DLR)—Institute of Planetary Research, 12489 Berlin, Germany
⁶Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA

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

^1,2Jean Charlier,¹Alice Aléon-Toppani,¹Rosario Brunetto,²Jérôme Aléon,³Ferenc Borondics
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14314]
¹Institut d’Astrophysique Spatiale, CNRS, Université Paris-Saclay, Orsay, France
²Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, Museum National d’Histoire Naturelle, CNRS UMR 7590, IRD, Paris, France
³SOLEIL Synchrotron, L’Orme des Merisiers, RD 128, Saint Aubin, France
Published by arrangement with John Wiley & Sons

Refractory inclusions (RIs) in chondrites are widely used as tracers of early solar system formation conditions. In the context of sample-return missions, a non-destructive and non-invasive analytical tool that can rapidly detect and characterize RIs in space samples during their early phase of study is highly needed. Here, we performed mid-infrared (MIR) fine-scale hyperspectral imaging over large fields of view to detect RIs in CM and CO chondrites. A database of MIR spectra of typical RIs minerals was built (1) to support future remote sensing observations in astronomical environments and (2) to develop a detection method based on machine-learning algorithms and spectral distance between sample and reference minerals. With this method, up to 96.5% of the RI content is detected in a meteorite section. Further comparison between scanning electron microscopy and spot analysis acquired in reflectance in the full MIR range shows that RIs can be classified following their mineralogy based on infrared (IR) properties. Finally, we show that the relative OH content of several RIs in CM chondrites determined from IR spectroscopy can be used to infer the extent of modification caused by aqueous alteration on the asteroidal parent body.

^1,2,3Juliane Gross et al. (>10)
Journal of Geophysical Research (Planets)(in Print) Link to Article [https://doi.org/10.1029/2024JE008585]
¹Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, Houston, TX, USA
²Lunar and Planetary Institute, Houston, TX, USA
³Department Earth and Planetary Sciences, The American Museum of Natural History, New York, NY, USA
Published by arrangement with John Wiley & Sons

During the six Apollo missions, astronauts collected 2196 lunar samples, nearly all of which have been studied over the past five decades. Six Apollo samples remained unexamined until 2019 and were saved to be analyzed by the next generation of lunar scientists using advanced modern laboratory facilities. Now more than 50 years after Apollo, NASA is returning to the Moon with Artemis and will return geologic samples from a different region of the lunar surface than Apollo. Curation will play an instrumental role in helping to prepare for the safe return of these valuable samples, ensuring their integrity during all stages of the missions, and thus maximizing their scientific return. To prepare for the return of these samples, NASA initiated the Apollo Next Generation Sample Analysis (ANGSA) Program to open previously unstudied samples including unopened double drive tube 73002 and 73001 (also vacuum-sealed) from the Apollo 17 mission to the Taurus-Littrow Valley. The ANGSA program was designed to function as a low-cost analog sample return mission and served as a testing ground to understand processes, update techniques, and prepare for the preliminary examination (PE) of the to-be-returned lunar samples with Artemis. New and advanced curation techniques were developed and applied to support the analyses of 73002/73001 during the PE. Furthermore, cutting-edge analytical instruments such as X-ray Computed Tomography were utilized to aid in PE that were unavailable during Apollo. These efforts are equipping the Artemis generation for future lunar missions and lessons learned from the PE of ANGSA samples will be directly applied to Artemis.

^1,2Kun Wang et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.01.043]
¹McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
²Department of Earth, Environmental, and Planetary Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
Copyright Elsevier

Space weathering has long been known to alter the chemical and physical properties of the surfaces of airless bodies such as the Moon. The isotopic compositions of moderately volatile elements in lunar regolith samples could serve as sensitive tracers for assessing the intensity and duration of space weathering. In this study, we develop a new quantitative tool to study space weathering and constrain surface exposure ages based on potassium isotopic compositions of lunar soils. We first report the K isotopic compositions of 13 bulk lunar soils and 20 interval soil samples from the Apollo 15 deep drill core (15004 – 15006). We observe significant K isotope fractionation in these lunar soil samples, ranging from 0.00 ‰ to + 11.77 ‰, compared to the bulk silicate Moon (–0.07 ± 0.09 ‰). Additionally, a strong correlation between soil maturity (Is/FeO) and K isotope fractionation is identified for the first time, consistent with other isotope systems of moderately volatile elements such as S, Cu, Zn, Se, and Cd. Subsequently, we conduct numerical modeling to better constrain the processes of volatile element depletion and isotope fractionation on the Moon and calculate a new K Isotope Model Exposure Age (KIMEA) through this model. We demonstrate that this KIMEA is most sensitive to samples with an exposure age lower than 1,000 Ma and becomes less effective for older samples. This novel K isotope tool can be utilized to evaluate the surface exposure ages of regolith samples on the Moon and potentially on other airless bodies if calibrated using other methods (e.g., cosmogenic noble gases) or experimental data.

¹B. Bultel,²M. Wieczorek,³Anna Mittelholz,^4,5Catherine L. Johnson,⁶Jérôme Gattacceca,^7,8,9Valentin Fortier,¹⁰Benoit Langlais
Journal of Geophyisical Research (Planets) Open Access Link to Article [https://doi.org/10.1029/2023JE008111]
¹GEOPS, Université Paris-Saclay, CNRS, Orsay, France
²Institut de Physique du Globe de Paris, Université Paris Cité, CNRS, Paris, France
³Department of Earth and Planetary Sciences, ETH Zurich, Zurich, Switzerland
⁴University of British Columbia, Vancouver, BC, Canada
⁵Planetary Science Institute, Tucson, AZ, USA
⁶Aix-Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
⁷Université Catholique de Louvain-la-Neuve, Earth and Life Institute, Louvain-la-Neuve, Belgium
⁸Laboratoire G-Time, Université Libre de Bruxelles, Bruxelles, Belgium
⁹Géosciences Montpellier, CNRS, Univ. Montpellier, Montpellier, France
¹⁰ de Planétologie et Géosciences UMR 6112, Nantes Université, Univ Angers, Le Mans Université, CNRS, Nantes, France
Published by arrangement with John Wiley & Sons

Strong magnetic fields have been measured from orbit around Mars over parts of the ancient southern highlands crust and on the surface at the InSight landing site. The geological processes that are responsible for generating strong magnetization within the crust remain poorly understood. One possibility is that intense aqueous alteration of crustal materials, through the process of serpentinization, could have produced magnetite that was magnetized in the presence of a global core-generated magnetic field. Here, we test this idea with geophysical and geochemical models. We first determine the magnetizations required to account for the observed magnetic field strengths and then estimate the amount of magnetite necessary to account for these magnetizations. For the strongest orbital magnetic field strengths, about 7 wt% magnetite is required if the magnetic layer is 10 km thick. For the surface field strength observed at the InSight landing site, 0.4–1.1 wt% magnetite is required if the magnetic layer corresponds to one or more of the three crustal layers observed in the InSight seismic data (with thicknesses from 8 to 39 km). We then investigate the minerals that are produced by aqueous alteration for various possible crustal compositions and water-to-rock ratios using a thermodynamic model. Magnetite abundances up to 6 wt% can be generated for dunitic compositions that could account for the strongest magnetic anomalies. For more representative basaltic starting compositions, however, more than 0.4 wt% can only be generated when using high water-to-rock ratios, which could account for the weaker magnetizations beneath the InSight landing site.

¹J. N. Levin,¹A. J. Evans,²J. C. Andrews-Hanna,¹I. J. Daubar
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008418]
¹Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
²Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd Tucson AZ, Tucson, AZ, USA
Published by arrangement with John Wiley & Sons

The distribution of KREEP—potassium (K), rare earth elements (REE), and phosphorus (P)—in the lunar crust is an important clue to deciphering the geochemical and thermal evolution of the Moon. Surface measurements of thorium abundance taken by the Lunar Prospector Gamma Ray Spectrometer (LP GRS) instrument have shown that KREEP is concentrated on the lunar nearside surface, mirroring the hemispheric asymmetry observed in the distribution of maria, crustal thickness, and topography. However, the overall lateral and vertical distribution of KREEP within the crust is poorly constrained, leaving uncertainty in estimates of bulk crustal thorium abundance and in the history and evolution of KREEP. In this study, we compared the overall lateral and vertical distribution of lunar KREEP in the upper crust by determining the thorium abundance of material excavated by complex impact craters. We find that the distribution of KREEP on the nearside is consistent with a layer of high-Thorium ejecta from the Imbrium impact mixing with underlying low-Th (<1 ppm) crustal material, suggesting the excavation of a sub-crustal KREEP reservoir with thorium abundances as high as 45–120 ppm by the Imbrium-forming impact. Imbrium ejecta alone does not explain the distribution of thorium on the lunar farside, particularly around the South Pole Aitken basin, suggesting other sources for farside thorium enrichments. Furthermore, our results refute the existence of a large-scale Thorium-enriched layer in the upper 16 km of the farside crust.