¹M. Yesiltas,¹T. D. Glotch
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70067]
¹Department of Geosciences, Stony Brook University, Stony Brook, New York, USA
Published by arrangemetn with John Wiley & Sons

CM chondrites have undergone varying degrees of aqueous alteration and thermal metamorphism on their parent bodies. Consequently, the petrologic grade of CM chondrites spans the entire type 2 scale (e.g., types 2.0–2.9). A 12236 is a very primitive petrologic type 2.9 carbonaceous chondrite that offers a unique window into the complex formation and evolution histories of CM chondrites. Based on its chemical composition, it is one of the least altered CM chondrites identified to date and one of the most primitive meteorites. Here, we present a comprehensive characterization of the organic and inorganic constituents of A 12236, determined through electron microscopy, micro-Raman, and s-SNOM nano-FT-IR spectroscopy. We identified FeNiS phases, including pentlandite, pyrrhotite, and troilite, within a fine-grained matrix composed predominantly of crystalline and amorphous silicates, including phyllosilicates. Raman spectroscopic results suggest that A 12236 experienced less thermal metamorphism than type 3 carbonaceous chondrites and contains polyaromatic organic matter with slightly differing structural order. Nano-FT-IR spectroscopy revealed chemically distinct aliphatic and aromatic organic phases, with observed compositional heterogeneity indicating variations in organic precursors and accreted materials. Correlation analysis highlights the complex associations between organic matter and phyllosilicates, along with evidence of differing aromatic compositions within the matrix. The varying abundances of nanoscale organics in different areas of A 12236 suggest that the organic matter is highly heterogeneously distributed within the matrix. Our findings demonstrate the effectiveness of nano-FT-IR spectroscopy for high-resolution, nondestructive analysis of extraterrestrial samples.

¹M. Simopoulou et al. (>10)
Journal of Raman Spectroscopy (in Press) Open Access Link to Article [https://doi.org/10.1002/jrs.6833]
¹Agricultural University of Athens, Laboratory of Mineralogy & Geology, Athens, Greece

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

¹Ke Zhu (朱柯),²Nao Nakanishi,³Jan Render,³Quinn R. Shollenberger,⁴Tetsuya Yokoyama,⁴Akira Ishikawa,⁵Lu Chen
The Astrophysical Journal Letters 984, L54 Open Access Link to Article [DOI 10.3847/2041-8213/adc89c]
¹State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, People’s Republic of China
²Department of Earth Sciences, Waseda University, Tokyo 169-8050, Japan
³Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA
⁴Department of Earth and Planetary Sciences, Institute of Science Tokyo, Tokyo 152-8551, Japan
⁵Wuhan Sample Solution Analytical Technology Co., Ltd., Wuhan, People’s Republic of China

The recently proposed Yamato-type (CY) chondrites share significant similarities with CI chondrites and Ryugu. We present major and trace elemental, Re–Os, and mass-independent Ti, Cr, and Fe isotope data for seven CY chondrites. The elemental data along with isotopic compositions reveal two distinct lithologies, here designated as CY1 and CY2, potentially originating from two different parent bodies. Although sharing similarities with CM chondrites, CY2 chondrites have distinct Cr isotope compositions, arguing against a close genetic relationship. The CY1 lithology exhibits elemental abundances similar to CI chondrites/Ryugu as well as Fe, Ti, and Cr isotope compositions that closely overlap with those of CI chondrites/Ryugu. This suggests that CI chondrites, CY1 chondrites, and Ryugu accreted in the same region of the solar system and may even originate from the same parent body. In fact, we find that the reduced water content and certain volatile element abundances alongside increased sulfide content and mass-dependent O isotope enrichments observed in CY1 compared to CI chondrites could be attributed to an impact-induced heating event on the CI parent body. This impact likely disrupted the CI parent body, resulting in the ejection of both CI and CY1 lithologies. Furthermore, given that there are presently only five known CI meteorite specimens, the close chemical composition between CY1 and CI chondrites substantially expands the data set for comparisons and referrals to the bulk solar system composition for nonvolatile elements. Finally, we propose that the “CY1” chondrites could be called “CI1T,” while the designation “CY” chondrites could be restricted to “CY2” samples.

^1,2Runwu Li, ^1,2Ming Tang, ¹Jiaxi Wang
Earth and Planetary Science Letters 671, 119650 Link to Article [https://doi.org/10.1016/j.epsl.2025.119650]
¹Key Laboratory of Orogenic Belt and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University, Beijing 100871, China
²Research Institute of Extraterrestrial Material (RIEMPKU), School of Earth and Space Sciences, Peking University, Beijing 100871, China
Copyright Elsevier

The samples returned by the recent Chang’e-5 (CE-5) mission confirmed active lunar magmatism at least two billion years ago, which challenged the long-held view of an inactive Moon through much of its lifespan. However, the origin of this extended lunar magmatism remains mysterious. The CE-5 lunar soil and basalt fragments exhibit a strong fractionation between middle and heavy rare earth elements, a phenomenon rarely observed in the Apollo samples. We confirm this fractionation as a primary magmatic signature with measurements of the pyroxenes. By coupling phase equilibria modeling and element partitioning calculations, we show that this fractionation can only be produced if the magma source contained ∼5-10% garnet at a minimum depth of ∼700 km. We suggest the primary CE-5 magma may have originated from the lunar lower mantle. For melting to occur, one possibility is that convection may have been sustained in the deep lunar mantle until at least two billion years ago. Alternatively, the CE-5 magma may have tapped the melt-bearing layer near the core, as indicated by recent seismic observations.

¹Sarah Joiret, ^1,2Alessandro Morbidelli, ³Rafael de Sousa Ribeiro, ⁴Guillaume Avice, ⁵Paolo Sossi
Eartha and Planetary Science Letters 671, 119625 Link to Aricle [https://doi.org/10.1016/j.epsl.2025.119625]
¹Collège de France, Université PSL, 75005 Paris, France
²Laboratoire Lagrange, Université Cote d’Azur, CNRS, Observatoire de la Côte d’Azur, Boulevard de l’Observatoire, 06304 Nice Cedex 4, France
³Sao Paulo State University, UNESP, Campus of Guaratingueta, Av. Dr. Ariberto Pereira da Cunha, 333 – 6 Pedregulho, Guaratingueta – SP, 12516-410, Brazil
⁴Université Paris Cité, Institut de physique du globe de Paris, CNRS, 75005 Paris, France
⁵Institute of Geochemistry and Petrology, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland
Copyright Elsevier

Mars finished forming while the solar nebula was still present, and acquired its primordial atmosphere from this reservoir. The absence of a detectable cometary xenon signature in the present-day Martian atmosphere suggests that the capture of solar nebular gas was significant enough to dilute later cometary contributions. By quantifying the mass of cometary material efficiently retained on Mars, we place a lower bound on the mass of the primordial Martian atmosphere. To test the robustness of our conclusions, we use cometary bombardment data from two independent studies conducted within a solar system evolutionary model consistent with its current structure. Our calculations show that, even under the most conservative scenario, the minimal mass of the primordial martian atmospheres would yield a surface pressure of no less than 2.9 bar. Such a massive nebular envelope is consistent with recent models in which atmospheric capture is strongly enhanced by the presence of heavier species on Mars – due to outgassing or redox buffering with a magma ocean.

^1,2Haojin Hu,^1,3Xiaojia Zeng,⁴Yanxue Wu,¹Yuanyun Wen,^1,5Xiongyao Li,^1,5Jianzhong Liu
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008868]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²University of Chinese Academy of Sciences, Beijing, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
⁴Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
⁵CAS Center for Excellence in Comparative Planetology, Hefei, China
Published by arrangement with John Wiley & Sons

The continuous bombardment of lunar surfaces by asteroids and comets has modified the chemical, mineralogical, and physical properties of the lunar crust. Oxidizing agents from these impactors could alter the redox conditions on the Moon. However, no Fe3+-bearing phase crystallized from impact melt has been reported in the lunar regolith. In this study, a submicron-sized magnetite grain was observed in lunar impact glass from the Chang’e-5 regolith breccia. Our results demonstrate that this magnetite was directly crystallized from the lunar impact melt under oxidizing conditions (IW‒WM buffer). We propose that these impact events could play a role in altering the oxidizing conditions of the lunar crust. Furthermore, impact-melt-crystallized magnetite grains may contribute to some extent to lunar magnetic anomaly signatures, but they are likely a very minor component relative to Fe-Ni alloys.

¹Pan Yan,¹Zhi Cao,¹Zhiyong Xiao,²Yanxue Wu,¹Yunhua Wu,²Mingchao Xiong,²Zilei Chen,³Lifeng Zhong,⁴Dengfeng Li,⁴Qiaofen Liu
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE008945]
¹Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai, China
²Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
³Southern Marin Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
⁴Guangdong Province Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, China
Published by arrangement with John Woiley & Sons

Microstructures are widespread on the surfaces of impact glasses in lunar regolith, recording intricate physical and chemical processes of regolith gardening. The Chang’e-6 mission returned the first regolith sample from the lunar farside, permitting investigation of regolith gardening on the farside and comparison with that on the nearside. Among over 400 glass particles handpicked from 1,500 mg of Chang’e-6 regolith, we investigated 178 impact glass beads, which were recognized based on their morphology, internal structure and geochemistry. The morphology and chemical compositions of microstructures on their surfaces are cataloged and compared with those reported on surfaces of lunar nearside samples, especially Chang’e-5 impact glasses. The various types of microstructures on surfaces of Chang’e-5 impact glasses are also observed on Chang’e-6 impact glasses, although the latter frequently exhibit a greater diversity of morphology and composition. The observations suggest that physical processes of regolith gardening are similar on the nearside and farside, which involve vapor, melt and/or solid phases, and with collision speeds much lower than those of extralunar impactors. On the other hand, there are other morphological types of microstructures on the surfaces of Chang’e-6 impact glass beads that were absent or rare on Chang’e-5 glasses, but they were reported on Apollo and Luna impact glasses. Their origin may be related to the older emplacement ages and/or more abundant exotic components in the protolith of Chang’e-6 regolith than that of Chang’e-5 regolith. During regolith gardening, chemical alterations of protoliths are nonuniform across the Moon, which are related to the contents of exotic components in the regolith.

^1,2Ritesh Kumar Mishra
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70050]
¹Independent Researcher, Bhagalpur, Bihar, 813211 India
²Veer Kunwar Singh University, Arrah, Bihar, 802301 India
Published by arrangement with John Wiley & Sons

Ca-Al-rich inclusions (CAIs), amoeboid-olivine aggregates (AOAs), and chondrules from the lowest petrographic type unequilibrated chondrites hold the potential to provide the best-preserved records of the origin and cosmochemical evolution of the solar system. Six CAIs, and three chondrules from Yamato (Y) 81020 (CO3.05), and one AOA and one spinel-bearing chondrule from Allan Hills (ALHA)77307 (CO3.03) were analyzed for 26Al-26Mg (t1/2 = 0.72 Ma) short-lived now-extinct radioisotope decay systematics. Five CAIs from Y-81020 and an AOA from ALHA77307 show a small range of abundance of 26Al/27Al from ~4.5 × 10−5 to 3.2 × 10−5. The inferred abundances in these relatively small-sized CAIs and AOA suggest their formation and/or resetting during distinct episodes spanning a few million years. The inferred time of formation of these small CAIs and AOA from the lowest petrographic type in Y-81020 and ALHA77307 is consistent with the previous results of high-precision analyses of three CAIs from Y-81020. The obtained results in CO chondrites are also in agreement with CR chondrites and with an order of magnitude larger-sized CAIs in CV (Vigarano) chondrites. 26Al/27Al abundances in the three analyzed chondrules imply their formation within the typical range of ~1 to 2 million years after the formation of CAIs. The observed 26Al/27Al abundances and initial magnesium isotopic compositions of these small CAIs and AOA in the weakly metamorphosed CO chondrites are in consonance with the previous studies of CAIs and AOAs in CV chondrites that inferred the formation and evolution of these objects from a homogeneous reservoir that existed at the birth of the solar system.

¹Nicolas P. Walte,²Max Collinet,³Cyrena A. Goodrich
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70063]
¹Heinz Meier-Leibnitz Centre for Neutron Science (MLZ), Technical University Munich, Garching, Germany
²Institute of Life, Earth and Environment (ILEE), University of Namur, Namur, Belgium
³Lunar and Planetary Institute, USRA, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

Ureilites are carbon-rich ultramafic achondrites that display unique textures, including strips of metal and carbon phases situated along grain boundaries and in fractures. Shock metamorphism observed in ureilites suggests an episode of brittle deformation caused by impact disruption of their parent body. The origin of carbon and metal has long been debated; in particular, whether either is endogenous or at least partly exogenous. We conducted experiments to simulate the metal-carbon textures and constrain their origin. Two model systems were investigated: (A) intrusion of FeS melt (analog for metal) into an olivine matrix containing dispersed graphite and (B) intrusion of graphite into a matrix containing dispersed FeS. After static annealing at 0.5–2 GPa and 1300°C, the samples were deformed at high strain rates to simulate an impact event. The microstructures of system A most closely resembled the textures observed in medium to low-shock main group ureilites, supporting an endogenous origin of carbon and a largely exogenous origin of metal. The grain boundary linings of ureilites were formed by impactor metal that intruded along grain boundaries and mixed with locally mobilized carbon. Hence, we establish a direct connection between the metal-carbon textures in ureilites and the collision history of their parent body.

^1,2Neha,¹S. Natrajan,¹K. K. Marhas
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE009101]
¹Physical Research Laboratory, Ahmedabad, Gujarat, India
²Gujarat University, Ahmedabad, Gujarat, India
Published by arrangement with John Wiley & Sons

Raman spectroscopic investigation of chemically separated insoluble organic matter (IOM) from six aubrites and five enstatite chondrites revealed a bimodal range of temperatures spanning from ∼200 to ∼1,000°C points toward heterogeneously altered organics. Temperatures derived from graphitized or partially graphitized IOM from aubrites are similar to those reported earlier by mineral thermometry (∼900–1,000°C) and their presence in our samples, despite peak temperatures falling significantly below the temperature threshold for graphitization, suggests the involvement of metal-catalyzed graphitization processes. The absence of an exciton peak in X-ray absorption near edge structure spectra and the temperatures inferred from Raman spectroscopy suggest short-term heating of IOM, potentially linked to impact-related heating within the aubrite parent body (AuPB). The diverse temperature obtained for the aubrites in this study possibly indicates that the source of these organics could either be indigenous, that is, preserved during partial melting (incomplete differentiation of AuPB) or exogenous, that is, delivered through impact. High-resolution transmission electron microscopy analysis reveals diverse IOM structures ranging from amorphous carbon to highly graphitic lamellar carbon phases and nanoglobules. Notably, the identification of nanoglobules, a feature typically associated with primitive chondrites, within one aubrite sample suggests the incorporation of exogenous organic material, possibly derived from primitive chondritic impactors.