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.

^1,2Ke Zhu, ³Martijn Klaver, ^4,5,6Wei-Biao Hsu, ⁷Harry Becker, ⁸Lu Chen, ⁹Qi Chen
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.10.009]
¹Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, United Kingdom
²State Key Laboratory of Geological Processes and Mineral Resources, Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
³Institut für Mineralogie, Westfälische Wilhelms-Universität Münster, Corrensstraße 24, 48149 Münster, Germany
⁴CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China
⁵State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macau
⁶School of Earth Sciences and Engineering, International Center for Isotope Effects Research, Nanjing University, Nanjing 210023, China
⁷Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, 12249 Berlin, Germany
⁸Wuhan SampleSolution Analytical Technology Co., Ltd, Wuhan, China
⁹Department of Earth Science & Environmental Change, University of Illinois at Urbana Champaign, Urbana, IL, United States
Copyright Elsevier

To understand accretion and differentiation of Mars, we report high-precision mass-dependent Ni (siderophile and chalcophile) isotope data of 37 bulk Martian meteorites. Large δ60/58Ni variations observed among these Martian meteorites are attributed primarily to magmatism and Ni diffusion in zoned olivine and sulfide. Shergottites show systematically higher Mg# and lower δ60/58Ni values relative to nakhlites, which can be caused by olivine crystallization, consistent with the Ni isotope fractionation factor between olivine and melt. Two Ni-rich chassignites (Martian dunites) provide the best current estimate of the upper limit of δ60/58Ni of bulk silicate Mars (BSM): 0.110 ± 0.031 ‰, since olivine crystallization causes Ni isotope fractionation. Subtracting a presumably chondritic contribution by late accretion, the proto-BSM should possess a δ60/58Ni of ≤ 0.074 ‰ that is lower than the average of chondrites (∼0.24 ‰). This sub-chondritic value of Martian mantle suggests the sulfur-rich core formation has not caused Ni isotope fractionation, because the sulfide and Martian sulfur-rich core is believed to enrich in light Ni isotopes. Instead, Ni isotope differences between Earth, Mars, Vesta, and the ureilites can be inherited from non-bulk chondritic precursor materials.

^1,2S. Iannini Lelarge,^2,3M. Masotta,^2,3L. Folco,⁴T. Ubide,^2,5M.D. Suttle,^6,7L. Pittarello
Geochemistry (Chemie der Erde) 88, 126293 Link to Article [https://doi.org/10.1016/j.chemer.2025.126293]
¹Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via Moruzzi 1, 56124 Pisa, Italy
²Dipartimento di Scienze della Terra, Università di Pisa, Via Santa Maria 53, 56126 Pisa, Italy
³CISUP, Centro per l’Integrazione della Strumentazione Università di Pisa, Lungarno Pacinotti 43, Pisa 56126, Italy
⁴School of Earth and Environmental Sciences, The University of Queensland, Brisbane 4102, QLD, Australia
⁵School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
⁶Naturhistorisches Museum, Mineralogisch-Petrographische Abteilung, Burgring 7, 1010 Vienna, Austria
⁷Department of Lithospheric Research, University of Vienna, Josef-Holaubek-Platz 2,1090 Vienna, Austria
Copyright Elsevier

We conducted high-pressure (1 GPa) melting experiments (1100–1400 °C) on the equilibrated ordinary chondrite DAV 01001 (L6) to investigate partial melting scenarios of planetary embryo in the early solar system. At 1100 °C, no melting of the silicate phase is observed, and the initial chondritic texture is preserved, but the metallic-sulphidic phases formed two immiscible Fe–Ni and S-rich liquids. Melting of silicate minerals began at 1200 °C, progressing from plagioclase to high-Ca and low-Ca pyroxene and olivine. As melting advanced, the formation of new olivine and low-Ca pyroxene resulted in the production of trachy-andesitic melt at 1200 °C, basaltic trachy-andesitic melt at 1300 °C, and andesitic melt at 1400 °C. These silicate melts have chemical similarities with some anomalous achondrites (e.g., GRA 60128/9). At the same time, minerals of new formation resemble those of primitive achondrites (e.g., brachinites, ureilites, IAB silicate inclusions, acapulcoites and lodranites). The rapid mineral-liquid re-equilibration suggests that basaltic liquids can form only above 1400 °C and that relatively high degrees of melting (>20 %) and crystallisation are necessary to explain the observed diversity of achondritic lithologies. These findings suggest that partial melting and recrystallization processes within planetary embryos could have played a critical role in the early solar system, contributing to the early differentiation of planetary bodies and the diversity of achondritic lithologies, including (but not limited to) alkali-rich achondrites.

^1,2Seann J. McKibbin,^3,4Lutz Hecht,^5,6Matthew S. Huber,²Christina Makarona,^7,8Stepan M. Chernonozhkin,²Philippe Claeys,²Steven Goderis
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70064]
¹Geowissenschaftliches Zentrum, Abteilung für Geochemie und Isotopengeologie, Georg-August-Universität Göttingen, Göttingen, Germany
²Archaeology, Environmental Changes, and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
³Museum für Naturkunde Berlin, Leibniz Institut für Evolutions und Biodiversitätsfoschung, Berlin, Germany
⁴Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany
⁵Planetary Science Institute, Tucson, Arizona, USA
⁶University of KwaZulu-Natal, Durban, South Africa
⁷Department of Chemistry, Atomic & Mass Spectrometry A&MS Research Unit, Ghent University, Ghent, Belgium
⁸Montanuniversität Leoben, General and Analytical Chemistry, Leoben, Austria
Published by arrangement with John Wiley & Sons

Main group pallasite meteorites (PMG) are samples of an early, highly differentiated magmatic planetesimal dominated by olivine and metal-sulfide-phosphide assemblages with accessory chromite among other phases. This mineralogy reflects mantle- and core-related reservoirs, but the relative contributions of each and the overall petrogenesis are obscured by high degrees of protolith melting. Here, we present new data on the chemistry of chromite in these meteorites and review previous datasets. The purely lithophile elements Mg and Al partition into chromite via (Mg,Fe)(Al,Cr)2O4 and mainly reflect interactions with olivine and basaltic melt, respectively. Chromite cores are virtually always more aluminous than rims, and while MgO contents were likely reset during slow cooling, their Al2O3 contents are more robust and were largely set during the period of silicate magmatism. Main group pallasite chromites display bimodality in Al2O3 contents, with peak concentrations at ~7.7 wt% and below 6 wt%, which is unlike any other achondrite chromite population. Some chromites have very low Al2O3 contents (~0.01 wt%) due to formation in the absence of silicate melt, that is, via exsolution of Cr from cooling liquid metal. High-, low-, and very low-Al2O3 chromites in these meteorites broadly reflect relict, prograde, and retrograde periods of planetesimal heating followed by cooling. The Al2O3 contents of the chromites in many other achondrites and equilibrated chondrites are similar to the higher values in pallasites, with most greater than 3 wt%. This suggests that meteoritic chromite is a significant sink for 26Al during its life as a heat source for planetesimal differentiation. To first order, it may be responsible for ~25%–50% (i.e., about one third) of heating in partially depleted mantles.

¹L. Miché Aaron-Hennig, ²Kim Seelos
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116835]
¹Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
²Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723, USA
Copyright Elsevier

Understanding the distribution and provenance of hydrated minerals within Noachian terrains is essential to deciphering Mars’ crustal formation and alteration history. The phyllosilicate and carbonate minerals typically found within Noachian geologic units, for instance, have been attributed to a warmer, wetter climate that preceded a transition to the sulfate-dominated, colder, drier, and more acidic conditions in the Hesperian and Amazonian. However, these broad associations may not hold true locally. In Tyrrhena Terra, the heart of the Noachian-aged cratered highlands, three isolated craters host an unusual occurrence of hydrated sulfates alongside a variety of other alteration minerals more typically associated with the Noachian era. This paper investigates the presence of these outcrops in order to understand their origin, relationship to these co-located minerals, and implications for aqueous history and crustal evolution of Mars. Using Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data along with other contextual remote sensing data, we present a mineralogical mapping and spectral analysis of primary and secondary minerals at each location where sulfates are observed. Based on our characterization, we have constrained the formation of the sulfates to be associated with epithermal alteration or sulfide oxidation rather than impact or mechanically induced alteration. This suggests a complex sequence of aqueous alteration, potentially involving one or more steps, which we intend to explore further in future studies. The discovery of these sulfate minerals within predominantly phyllosilicate and carbonate territories challenges the conventional timeline of Mars’ climate evolution, hinting that transitions between climatic epochs may have overlapped or been more regionally varied than previously thought.