¹Jiawei Zhao et al. (>10)
American Mineralogist 111, 376-393 Link to Article [https://doi.org/10.2138/am-2025-9877]
¹State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan 430074,
China
Copyright: The Mineralogical Society of America

Pyroxene is a primary constituent mineral in basaltic lunar regolith. These minerals form through the cooling and crystallization of lunar basaltic magma and are subsequently altered by impact events. Thus, pyroxene can serve as a significant indicator for interpreting lunar magmatic processes and impact phenomena. For lunar samples that are mostly mafic and frequently shocked to various degrees, deciphering the effect of shock on pyroxene is necessary for a better understanding of the primary magmatic processes. However, previous studies have neglected to investigate the impact metamorphism of pyroxene in lunar regolith and the potential compositional changes that may result from such impacts. Lunar regolith samples returned by the Chang’E-5 (CE-5) mission are reworked from a monolithic mafic protolith with well-constrained compositions and record strong to mild shock effects that are widespread in the samples. The returned samples provide an excellent chance to distinguish the signatures of impact processes from magmatic activities. Here we report microstructural and compositional variations in a shocked pyroxene within a basaltic clast from CE-5 lunar regolith, which were analyzed by Raman spectroscopy, analytical scanning electron microscopy, electron probe microanalysis, and scanning transmission electron microscopy. The shock microstructures are characterized by the glide system of dislocation [001](100), pigeonite formation induced by shock-related deformations, and solid-melt partitioning and localized frictional melting at grain boundaries or within pyroxene. Combined with the occurrence of shock twins in ilmenite adjacent to the shock melt vein, these shock phenomena are approximately indicative of low-to-moderate shock pressure (9–17 GPa). Most parts of the pyroxene have abnormal Raman peaks at ∼822 cm−1, suggesting the substitution of Si4+ by Al3+ in the tetrahedral site of this shocked pyroxene structure, and this characteristic is recognized as a shock indicator. Evidence from the morphology and elemental distribution of pigeonite within host augite suggests that the Si-Al substitution is consistent with the pigeonite formation, which is triggered or modified by shock-induced deformations and local frictional melting under the fast shear stress. The multiple trends of composition evolution in this single shocked pyroxene reflect sequential processes of magma crystallization, shock-related exsolution, and frictional melting. Our findings indicate that shock effects in pyroxene under low-to-moderate shock conditions can induce changes in composition and structure, and may obscure the evidence of magmatic evolution in pyroxene.

^1,2Xinxin Yan, ³Xinzhuan Guo, ³Yun Zhou, ^1,2Yuping Song, ⁴Qingshan Zhang, ^1,2Meng Lv
Earth and Planetary Science Letters 684, 120009 Link to Article [https://doi.org/10.1016/j.epsl.2026.120009]
¹Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550081, China
²University of Chinese Academy of Sciences, Beijing 100049, China
³State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550081, China
⁴China University of Mining and Technology, Xuzhou 221116, China
Copyright Elsevier

The thermal conductivity and diffusivity of mantle minerals fundamentally control planetary cooling rates. Orthopyroxene is a major constituent of the lunar mantle, yet the influence of trace water on its thermophysical properties under high-pressure and high-temperature conditions relevant to the lunar interior has remained unquantified. Here, we present high P–T measurements of these properties for synthetic enstatite containing 0–427 ppm H2O using an enhanced transient plane source method. Our results demonstrate that even trace water drastically reduces thermal transport efficiency by enhancing phonon scattering. Incorporating these data into lunar thermal evolution models reveals that a hydrated mantle maintains significantly higher internal temperatures than an anhydrous system over geologic time. By reconciling our model geotherms with the solidus of various lunar mantle constituents and with seismic constraints on the largely solid modern mantle, we constrain the bulk water content of the lunar mantle to around 300 ppm. This work redefines the thermal state of the Moon and provides a critical mechanism for explaining its prolonged magmatic evolution.

^1,2Yao Sun, ²Jonas Tusch, ¹Xiaorui Fan, ¹Jifeng Xu, ³Chao Li, ⁴Kristoffer Szilas, ²Carsten Münker, ¹Jingao Liu, ²Mario Fischer-Gödde
Earth and Planetary Science Letters 684, 120012 Link to Article [https://doi.org/10.1016/j.epsl.2026.120012]
¹State Key Laboratory of Geological Processes and Mineral Resources, and Frontiers Science Center for Deep‐time Digital Earth, China University of Geosciences, Beijing 100083, China
²Institut für Geologie und Mineralogie, Universität zu Köln, Cologne 50674, Germany
³National Research Center for Geoanalysis, Beijing 100037, China
⁴Natural History Museum of Denmark, University of Copenhagen, Copenhagen 1350, Denmark
Copyright Elsevier

The mass-independent Mo isotope composition of the Bulk Silicate Earth (BSE) bears great potential to investigate the origin of the Earth’s latest 10–20% planetary building blocks. However, currently different estimates for the Mo isotope composition of the BSE render constraints on the composition of late-stage accretionary materials difficult. To address this issue and to revisit the Mo isotope composition of the BSE, we report high-precision molybdenum isotope data for a comprehensive set of terrestrial molybdenites from different locations around the globe covering mineralization ages that extend from the Archean to the Phanerozoic. The molybdenite results are used to constrain the Mo isotope composition of the BSE as follows: ε92Mo = 0.04 ± 0.06, ε94Mo = 0.03 ± 0.03, ε95Mo = 0.01 ± 0.01, ε97Mo = 0.02 ± 0.02, ε100Mo = 0.05 ± 0.06 (n = 16, 95% confidence interval, relative to the NIST SRM 3134 Mo standard). In contrast to previous studies, no resolvable ε94Mo and ε95Mo anomalies were observed, suggesting a BSE composition with predominantly non-carbonaceous chondrite provenance. Considering the analytical uncertainties of our new BSE estimate and literature data for carbonaceous and non-carbonaceous meteorites, it remains a viable option that 12±10% of the present-day Mo budget in the BSE derives from carbonaceous meteorite material delivered during late-stage accretion. This amount of Mo is consistent with the fraction of Mo that was delivered to Earth during its final 0.5% of accretion by the late veneer.

¹Roger L. Gibson,¹S’lindile S. Wela,¹Leonidas C. Vonopartis,¹Marco A. G. Andreoli
Meteoritics & Planetary Science (in Press) Open Access Link to Articles [https://doi.org/10.1111/maps.70136]
¹School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
Published by arrangement with John Wiley & Sons

A core drilled through shocked and faulted Archean granitoid gneisses and dolerites in the eroded peak ring of the 70–80 km diameter Morokweng impact structure intersects multiple centimeter- to meter-wide clastic-matrix breccias containing a polymict clast population of lithic and mineral clasts and altered, millimeter- to centimeter -size, melt clasts. These polymict melt-bearing (PMB) breccias occur both as discrete dikes and in meter- to decameter-wide composite breccia intersections where they are intimately associated with cataclasite and pseudotachylite. Petrographic and bulk-rock geochemical analysis confirms that the PMB breccias comprise fragmental and melt material derived exclusively from the granitoid and doleritic wallrocks, with local geochemical deviations attributable to metasomatic hydrothermal alteration. Notwithstanding their almost complete replacement by smectite and zeolite assemblages, the melt clasts display textural and compositional characteristics identical to the pseudotachylite dikes. Composite lithic-melt clasts indicate an intimate association of melting with cataclasis and comminution prior to their incorporation into the PMB breccias. While most melt clasts display sharp, angular shapes, indicating brittle fracturing, local preservation of delicate filaments intruding the adjacent clastic matrix and bulbous to cuspate-lobate melt clast margins against the matrix indicate incorporation into the breccias while still molten and/or plastic. We propose that the PMB breccias formed by a combination of dynamic injection of friction melt into the cataclasite portions of large fault zones and the development of shear-induced Kelvin–Helmholz instabilities along the melt-cataclasite interface during ongoing fault slip. Melt injection into brecciated wallrock and smaller fractures hosting incoherent cataclasite may have been assisted by a pumping-suction mechanism driven by complex, rapidly changing, block movements during crater wall collapse and peak ring formation. Cooling of the pseudotachylite melts during continued shear or compression of the breccia zones led to their embrittlement and mechanical entrainment as fragments into the incohesive cataclastic fault material, producing the hybrid PMB breccia type. Although the complex strain patterns during peak ring formation could have played a role in extending the duration of shear movements affecting the breccias, we propose that the sequence of cataclasis, frictional melting, melt injection, quenching, brecciation of quenched melt, and melt clast entrainment necessary to produce the PMB breccias can be reconciled with a single, continuous, long-duration, large-magnitude, slip event during collapse of the transient crater wall.

¹Maximilian P. Reitze, ¹Iris Weber, ¹Andreas Morlok, ¹Harald Hiesinger, ¹Johannes Benkhoff, ¹Jan Hendrik Pasckert, ¹Nico Schmedemann, ¹Thomas Heyer, ²Solmaz Adeli
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117073]
¹Institut für Planetologie, Universität Münster, Wilhelm-Klemm Str. 10, Münster, 48149, Germany
²Deutsches Zentrum für Luft- und Raumfahrt (DLR, Rutherfordstr. 2, Berlin, 12489, Germany
Copyright Elsevier

In this work, we propose a new potential mechanism for the formation of the so-called hollows on Mercury, hypothesizing that they are composed of carbonatites—volcanic rocks that are exceedingly rare on Earth. To evaluate this hypothesis, mid-infrared spectroscopic measurements were performed on a rare, unaltered terrestrial carbonatite sample from Mount Ol Doinyo Lengai, Tanzania, composed primarily of the carbonate minerals nyerereite and gregoryite. For comparison, spectra of several common terrestrial carbonate minerals were also acquired. The collected spectra display characteristic features of carbonate minerals. Our analysis suggests that carbonatite rocks should be taken into account for several physical properties required for the formation of hollows on Mercury’s surface. These include appropriate thermal stability, chemical composition, and surface coloration. In particular, the eruption temperatures of terrestrial carbonatite lavas are less than 100 °C below Mercury’s estimated daytime surface temperatures. This thermal similarity makes the measured spectra relevant for the MERTIS instrument onboard the BepiColombo spacecraft, which will investigate Mercury’s surface mineralogy in near future.

¹Dian Ji, ¹Rajdeep Dasgupta, ¹Cin-Ty Lee
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.03.042]
¹Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX 77005, United States of America
Copyright Elsevier

The theory of the Moon’s formation via a giant impact, along with initial early sample analyses, suggested that the Moon is extremely volatile-depleted relative to the Earth. Yet, the petrologic studies of lunar melt inclusions and volcanic glasses over the last two decades suggested that water content in the lunar mantle is much higher (as high as 133 – 292 μg/g) than expected and is similar to the Earth’s shallow upper mantle. This high water concentration of the lunar mantle challenged prevailing models of the formation and early evolution history of the Moon, suggesting that not all volatiles were lost, or that impactors supplied additional volatiles. However, previous petrologic models of lunar primary melt water content reconstruction did not consider many key magma differentiation processes. Here, we model lunar magmatism taking into consideration the process of magmatic recharge and show that such a process can explain the anomalously high water abundances, along with other volatile elements such as S, F, and Cl, in Apollo sample 74220 basaltic melt inclusions, as well as the available volatile data of Apollo 79135 and 15597 basaltic to andesitic melt inclusions. Moreover, the model can also explain the MgO content and high-Ti nature of 74220 inclusions, since recharge results in ever-increasing incompatible element concentrations while buffering major element compositions. Therefore, other than deriving from a wet background mantle, we propose an alternative scenario that the water-rich lunar melts could originate from a water-poor (as low as 1–22 μg/g), primitive, magma ocean cumulate. The estimated extent of volatile depletion of the lunar interior varies with the vigor of the magmatic recharge process. Further studies are necessary to independently assess evidence of magmatic recharge, the melt replenishment frequency, and the impact of such a magma reservoir process in our understanding of lunar mantle-crust evolution.

¹Yuta Otsuki, ¹Ken-ichi Bajo, ^1,2Tomoya Obase, ³Rainer Wieler, ¹Hisayoshi Yurimoto
Earth and Planetary Science Letters 683, 120000 Link to Article [https://doi.org/10.1016/j.epsl.2026.120000]
¹Department of Natural History Sciences, Faculty of Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
²Department of Earth and Planetary Sciences, Institute of Science Tokyo, Meguro-ku, Tokyo, 152-8551, Japan
³Department of Earth and Planetary Sciences, ETH Zürich, 8092 Zürich, Switzerland
Copyright Elsevier

Lunar soils have been studied since the NASA/Apollo missions. Noble gas studies suggested that the soils contain two components of solar noble gases: solar wind (SW) implanted within <100 nm depths, and an isotopically heavier component attributed to solar energetic particles (SEPs) implanted to larger depths. Data from the NASA/Genesis mission revealed, however, that the isotopically heavy signature is a result of isotopic fractionation of solar wind ions upon implantation, thus the acronym fSW for fractionated solar wind. However, previous analyses lacked a quantitative depth scale for fSW. Here we report high-spatial-resolution depth profiling of He, Ne, and Ar from the SW in three ilmenite grains from Apollo 17 soil 71501, using a time-of-flight secondary neutral mass spectrometry. Noble gases are highly concentrated within the topmost 100 nm depth from the surface. The 20Ne/22Ne ratio decreases with increasing depth from the SW value of ∼14 to ∼11 at ∼50 nm depth. Our quantitative depth profiles give strong support that the isotopically heavy Ne observed in lunar samples is fSW, allowing to further refute the SEP hypothesis. The 4He/20Ne ratio from the three grains and 20Ne/36Ar from one of them are lower than the present-day SW composition, indicating a selective loss of light noble gases. Based on numerically simulated profiles, we suggest that this loss is caused by a defect-mediated effusion process.

¹J.C. Noest, ¹M.J. Sluis, ^1,2J. Alsemgeest, ¹H.J.L. Van der Lubbe, ¹S.J.A. Verdegaal, ¹F.M. Brouwer
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117068]
¹Geology and Geochemistry Cluster, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1105, 1081, HV, Amsterdam, the Netherlands
²Department of Applied Earth Sciences, Science and Earth Observation (ITC), University of Twente, Hallenweg 8, 7522, NH, Enschede, the Netherlands
Copyright Elsevier

Hydrothermal systems can provide a habitat for early life on planetary bodies throughout the Solar System. For Mars, impact-generated hydrothermal systems (IGHSs) are especially interesting, because of its high crater density and the presence of hydrous minerals in Martian craters. However, it is uncertain whether these hydrous minerals formed in an IGHS, or if they formed earlier and were then excavated by the impact. It is also unknown whether conditions in these systems are hospitable for life.
To gain further insight into these open questions, this study investigates two types of vein-forming hydrothermal alteration in the Vargeão Dome impact structure (Brazil) residing in basaltic host rock similar to the Martian surface. Rare Earth Element (REE) patterns of the veins and the surrounding host rock and stable C and O isotopes in calcite were studied using linear regression modelling and thermodynamic modelling to constrain fluid conditions.
REE analysis as proxy for major elements and modelling suggest that elevated amounts of Al, Fe, Mg, and to a lesser extent Na and Ca are needed for the formation of white and red veins. They also suggest that the white veins form under reducing conditions and with limited aquifer influence, whereas the opposite is true for the red veins. Stable isotope signatures indicate that all calcite formed from a meteoric fluid in the same hydrothermal stage as part of the white veins. Furthermore, the thermodynamic modelling suggest that this calcite precipitated from a fluid that underwent gradual heating from 27 to 55 °C combined with degassing of CO2. Together with observed calcite amygdales close to the vein rim and geodes outside of the impact structure, which are both isotopically similar to the calcite in veins, this suggests that the white veins all formed before the impact.
If Martian impact craters are similar to Vargeão Dome, the hydrous minerals are more likely to have been excavated by the impact and did not form as part of an IGHS. However, gradual heating in the Vargeão pre-impact hydrothermal system, as well as the high-nutrient content related to the hydrothermal system, could favour the development of mesophiles in impact-excavated systems on Mars.

¹Timo Hopp, ¹Shengyu Tian, ¹Thorsten Kleine
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117057]
¹Max Planck Institute for Solar System Research; 37077, Göttingen, Germany
Copyright Elsevier

Understanding the origin of the Earth requires determining the original formation location of its building material. Based on the similar Fe isotopic composition of Earth’s mantle and Ivuna-type (CI) chondrites, a prior study has argued that Earth formed by accretion of sunward-drifting pebbles from the outer Solar System. Here, using new high-precision Fe isotopic data, we show however that CI chondrites and Earth’s mantle have distinct Fe isotopic composition when the neutron-rich 58Fe is also considered. This observation rules out that the Fe in Earth’s mantle derives from CI chondrite-like material and demonstrates that Earth did not form by accretion of sunwards-drifting pebbles. We show that the Fe in Earth’s mantle instead derives from the inner Solar System, and has been partly or wholly delivered by bodies from the innermost disk that remained unsampled among meteorites. This provenance of terrestrial Fe is consistent with the classical model of Earth’s formation by hierarchical growth among inner Solar System planetesimals and planetary embryos.

^1,2,3,4Ke Zhu 朱柯, ⁵Peng Ni, ⁶Qi Chen, ⁷Mahesh Anand, ²Meng-Hua Zhu, ⁴Tim Elliott
Earth and Planetary Science Letters 683, 119974 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2026.119974]
¹State 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
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
³School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC 3800, Australia
⁴Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, United Kingdom
⁵Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095, USA
⁶Department of Earth Science & Environmental Change, University of Illinois at Urbana Champaign, Urbana, IL, USA
⁷School of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, United Kingdom
Copyright Elsevier

Although the Moon is thought to have formed through a giant impact between proto-Earth and a Mars-sized body, the processes responsible for the chemical and mass-dependent isotopic differences between Earth and Moon remain debated. We report high-precision mass-dependent Ni isotope data for 19 Apollo samples, including one dunite (72415), fifteen low-Ti basalts, and three high-Ti basalts, analyzed by double-spike technique using a multi-collector plasma-sourced mass spectrometer. The dunite 72415 shows an extremely high δ60/58Ni value of +1.80 ± 0.01‰, which we attribute to kinetic isotope fractionation from Ni diffusion during re-equilibration between olivine and a later melt. Diffusion modeling of Ni–Fe–Mg systematics reproduces the observed heavy Ni enrichment. In contrast, low-Ti basalts display a mean δ60/58Ni of 0.23 ± 0.20‰ (2SD), unaffected by cosmic-ray exposure, while high-Ti basalts are slightly isotopically lighter (0.06 ± 0.22‰, 2SD). Petrological modeling using pMELTS with recently constrained silicate mineral-melt fractionation factors suggests limited Ni isotope fractionation (<0.05‰) during lunar magma ocean crystallization and partial melting, yielding an estimated bulk silicate Moon (BSM) δ60/58Ni = 0.18 ± 0.20‰ (2SD). This overlaps with the bulk silicate Earth (BSE: 0.11 ± 0.07‰), indicating that Ni depletion in the lunar mantle, by a factor of ∼4 relative to Earth, can be caused by core formation (that does not fractionate Ni isotopes). However, our modelling shows evaporative loss of Ni can elevate δ60/58Ni value of < 0.23‰, which remains consistent with those of BSM within uncertainty. Hence, the mechanism of Ni evaporation cannot be ruled out.