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.

¹Toni Schulz,¹Christian Koeberl,^1,2Olivier Heldwein,³Bo-Magnus Elfers,⁴Jonas Tusch,⁵Stefan T. M. Peters,⁶Andreas Pack,⁴Carsten Münker
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70124]
¹Department of Lithospheric Research, University of Vienna, Vienna, Austria
²Institute of Social Ecology, University of Natural Resources and Life Sciences, Vienna, Austria
³Technische Universität Hamburg, Zentrallabor Chemische Analytik, Hamburg, Germany
⁴Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany
⁵Zentrum für Biodiversitätsmonitoring, Leibniz-Institut zur Analyse des Biodiversitätswandels, Hamburg, Germany
⁵Geowissenschaftliches Zentrum, Georg-August-Universität Göttingen, Göttingen, Germany
Published by arrangement with John Wiley & Sons

Archean impact spherule layers represent exceptional archives of extraterrestrial (ET) material, containing large amounts of ET highly siderophile elements (HSE) that dominate the bulk content of these elements. This enrichment makes them prime targets for testing additional impact tracers, such as ε182W and triple oxygen isotopes. We investigated samples from the Paleoarchean BARB5 drill core (Barberton Mountain Land, South Africa), which preserves four spherule layers with chondritic HSE contents and 187Os/188Os signatures. Tungsten isotope data from bulk spherule layer samples yield ε182W values indistinguishable from the bulk silicate Earth, most likely reflecting the limited sensitivity of the ε182W composition to detect meteoritic admixture. If present, such a component must lie within analytical uncertainties, limiting contributions to ≤6% for a chondritic endmember or ≤3% for an iron-meteorite endmember, unless a larger signal was erased by postimpact hydrothermal overprint. In addition, bulk triple oxygen data fall within Archean shale fields and do not show resolvable ET signatures, consistent with a chondritic contribution of at most ~5% given analytical uncertainties; elevated 18O values most likely reflect seawater alteration of glass spherules. Thus, despite clear HSE–Os isotope evidence for admixture of ET components, ε182W and oxygen isotopes yield no such information. This can be explained by plume condensation models predicting temporally separated fallout of refractory and volatile element carriers. To test this, we separated spherules, matrix, and mixed fractions from one of the four BARB5 beds. While the matrix hosts the highest HSE contents and least radiogenic 187Os/188Os, spherules have the lowest HSE contents and slightly more radiogenic 187Os/188Os signatures, with mixed fractions being intermediate. Together with highly siderophile interelement trends, these results most likely highlight stepwise condensation followed by early syn-depositional to diagenetic alteration, establishing Archean spherule beds as unique probes of early plume dynamics and impact processes.

¹Chi Ma,²Oliver Tschauner,³John G. Spray,⁴Zhongxu Pan
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70129]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
²Department of Geoscience, University of Nevada, Las Vegas, Nevada, USA
³Planetary and Space Science Centre, University of New Brunswick, Fredericton, New Brunswick, Canada
⁴School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China
Published by arrangement with John Wiley & Sons

We report a previously unknown aluminosilicate mineral, (Si0.91□0.09)Σ1.00(Al1.46□0.54)Σ2.00O4 with a vacancy-stabilized spinel-type structure (henceforth “SiAl-spinel”). This novel aluminosilicate occurs with coesite, stishovite, and majoritic garnet in a shock melt vein in metaquartzite from the outer collar of the Vredefort Dome, the eroded central uplift of the Vredefort impact structure of South Africa. Formation conditions for this new high-pressure, high-temperature phase are around 10 GPa and 1400°C, upon release from peak shock conditions. Based on its composition and formation conditions, this new high-pressure, high-temperature phase is predicted to be a common occurrence in terrestrial impactites and in subducted slabs.

^1,2Lidia Pittarello,³Valeria De Santis,³Laura Carone,⁴Giovanni Pratesi,⁵Mauro Gemmi,⁵Paola Parlanti,⁶Andreas Steiger-Thirsfeld,⁷Alessandro Di Michele,³Gabriele Giuli
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70134]
¹Naturhistorisches Museum, Mineralogisch-Petrographische Abteilung, Vienna, Austria
²Department of Lithospheric Research, University of Vienna, Vienna, Austria
³Geology Divison, School of Science and Technology, University of Camerino, Camerino, Italy
⁴Department of Earth Sciences, University of Firenze, Firenze, Italy
⁵Electron Crystallography, Istituto Italiano di Tecnologia, Pontedera, Italy
⁶Technische Universit€at Wien, University Service Center for Transmission Electron Microscopy, Vienna, Austria
⁷Department of Physics and Geology, University of Perugia, Perugia, Italy
Published by arrangement with John Wiley & Sons

The occurrence of ringwoodite in shocked L6 ordinary chondrites has been frequently reported, mostly within shock veins. Only recently, ringwoodite has also been found in a fragment from the Alfianello meteorite, occurring as rim or core of olivine clasts in impact melt pockets, in lamellae crosscutting olivine grains in the host rock, and in fine-grained aggregates in association with wadsleyite. In all cases, ringwoodite shows a higher Fe/Mg ratio than the original olivine, whereas wadsleyite shows a lower Fe/Mg ratio than the original olivine. Detailed TEM studies of the occurrence of both high-pressure polymorphs allow the identification of the most likely formation process, explaining the coexistence of these polymorphs. The lack of any crystallographic relationships but the complementary Fe/Mg ratios supports formation of the assemblage through fractional crystallization from impact melt under high (shock) pressure conditions. However, the other occurrences of ringwoodite reported in the same sample, traditionally interpreted as resulting from solid-state transformation, emphasize the heterogeneity of distribution of shock effects and shock-induced processes recorded in a single meteorite.

^1,2,3M. R. Boyd,^1,2M. J. Genge,⁴A. G. Tomkins
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70123]
¹Department of Earth Science and Engineering, Imperial College London, London, UK
²Natural History Museum, London, UK
³Grantham Institute – Climate Change and the Environment, Imperial College London, London, UK
⁴School of Earth, Atmosphere and Environment, Monash University, Melbourne, Victoria, Australia
Published by arrangement with John Wiley & Sons

Natural microspherules are formed by high-temperature processes and are present throughout the geologic record to the present day. We report the discovery of large numbers of microspherules recovered from a rock pavement in the Pilbara region, Western Australia. Textures range from glassy to coarse-grained, with many particles containing crystallites, vesicles, and relict grains. Compositions are non-chondritic and are either dominated by silicates or Fe-Ti-bearing oxides. Spherule and relict grain compositions show strong affinities to the mineralogy of the underlying rock, a Paleoarchean granite gneiss. Bulk compositions suggest formation by a localized melting process with precursors dominated by individual pre-existing minerals, with minimal mixing. Numerical modeling of the formation of spherules suggests formation by rapid quenching, possibly from melt droplets. Modeled cooling times are consistent with compositions that indicate limited evaporation. The compositions and textures of these spherules are not compatible with either microtektites formed by meteor impact or micrometeorites formed by the atmospheric entry of cosmic dust and are instead interpreted to have formed via lightning strikes. Spherules generated by lightning strikes may be present in the geologic record and thus could be used as a paleoclimate proxy where other signatures, such as main mass fulgurites, have not survived.

¹Neeraj Srivastava et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70121]
PRSS, PSDN, Physical Research Laboratory, Ahmedabad, India
Published by arrangement with John Wiley & Sons

Estimating mineral abundance in meteorites provides crucial information about the early solar system and planetary formation processes. This study presents a new empirical approach for the estimation of modal abundance of olivine (Ol), high-calcium pyroxene (HCP), and low-calcium pyroxene (LCP) using band area ratio (BAR), a spectral parameter derived using reflectance spectroscopy. Using spectral data of 22 mineral mixtures acquired from the RELAB spectral library, the BAR values were initially calculated. These BAR values were then plotted against Ol% and HCP%, and based on the trends observed, a set of equations was formulated to get the initial estimate of mineral abundances. To apply these to actual samples, an error reduction framework has been developed that involves determination of a class-specific correction factor (CF) for H, L, and LL types of ordinary chondrites (OCs) to account for the presence of other minerals, metals, and impurities. The CF is a quantitative adjustment that is subtracted from the initial estimates to align calculations with the actual values. After application of the CF, the 1σ uncertainties associated with the abundance estimates were found to be ±1.85% for Ol, ±0.91% for HCP, and ±1.63% for LCP. The study demonstrates the estimation of the mineral abundances of seven OCs, using spectral analysis conducted at the Planetary Remote Sensing Laboratory (PRSL), Physical Research Laboratory (PRL). The proposed approach is robust even for bulk samples analyzed under different viewing geometries and provides a rapid, nondestructive alternative to traditional techniques for mineral abundance estimation in meteorites, planetary samples, and analogs.

¹Martyna Jakubowska,¹Jolanta Gałązka-Friedman,²Marek Woźniak,³Krzysztof Szopa,⁴Katarzyna Brzózka,⁵Barbora Pospíšilová,⁶Agnieszka Grabias
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70122]
¹Faculty of Physics, Warsaw University of Technology, Warsaw, Poland
²Faculty of Biology, University of Warsaw, Warsaw, Poland
³Faculty of Natural Sciences, University of Silesia, Sosnowiec, Poland
⁴Faculty of Mechanical Engineering, Casimir Pulaski Radom University, Radom, Poland
⁵Faculty of Science, Palack´y University Olomouc, Olomouc, Czech Republic
⁶Łukasiewicz Research Network—Institute of Microelectronics and Photonics, Warsaw, Poland
Published by arrangement with John Wiley & Sons

The paper presents a modified version of the 4M method, which is the latest method of classifying ordinary chondrites, based on their Mössbauer spectra measured at room temperature. The proposed changes, including the introduction of a new criterion for assessing which group (H, L, or LL) the meteorite being tested belong to, are expected to improve the plausibility of classification by the 4M method. The modification makes use of the Bayesian analysis and the maximum a posteriori probability. This modified version of the 4M method was tested by attempting to classify 20 samples of ordinary chondrites: 8 of type H, 7 of type L, and 5 of type LL. The results were compared with those obtained by the classical method of ordinary chondrite classification. The vast majority of classification tests performed using the new version of the 4M method were consistent with the classical method for group assignment, except for one L-type sample that was classified differently. It was also shown that the introduction of a new criterion resulted in a significantly better agreement with the established classification than in the case of the level of similarity criterion used in the previous version of the 4M method.