¹A. Sedaghat, ¹C. McLeod, ²M. Loocke, ³B. Shaulis
Icarus (in Press) Open Access Link to Article [DOI: 10.1016/j.icarus.2026.117331]
¹Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA
²Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA
³Trace Element and Radiogenic Isotope Laboratory (TRAIL), University of Arkansas, Fayetteville, AR 72701, USA
Copyright Elsevier

Through integrated textural, mineralogical, and geochemical studies, symplectites provide fundamental constraints on the evolution and stability of geological systems. The returned 2018–2019 Antarctic Search for Meteorites Dominion (DOM) Range lunar meteorites contain ubiquitous three-phase symplectites consisting of fayalitic olivine (Fa), Ca-Fe-rich pyroxene (Px), and a silica phase (Si). Here, the textures and compositions of two textural symplectite types in DOM 18509 and DOM 18543 are investigated. Typical symplectites are characterized by a relatively uniform distribution of Fa-Px-Si and fine grain sizes (≤5 μm). Fayalite is Fe-rich (Fa_91–96) with associated pyroxene at Wo_31–40En_6–11Fs_51–61. Bulk compositions determined via reconstruction and broad beam analyses yielded lunar pyroxferroite compositions. The preservation of rare pyroxferroite in lunar materials is reported for DOM 18509: Wo_12-13En_9-10Fs_77–78. In contrast, non-typical symplectites exhibit variable grain sizes and consist of a Ca-rich host pyroxene (Wo_23–40En_8-18Fs_49–68) containing blebs of olivine (Fa_86–95) and silica. Reconstruction for the bulk precursor material yields a metastable pyroxene (Wo_24-26En_12-16Fs_58–64). While both symplectite types are interpreted as subsolidus breakdown products during slow cooling, their formation is associated with different breakdown pathways from distinct precursor phases. During late-stage crystallization in highly evolved lunar basaltic systems, pyroxene compositions enter the forbidden zone. At this stage, metastable Ca-rich pyroxene forms, followed by crystallization of metastable pyroxferroite during extreme Fe-enrichment. Subsequently, non-typical symplectites form through the subsolidus multistep breakdown of metastable Ca-rich pyroxene, whereas typical symplectites form through the direct subsolidus breakdown of pyroxferroite. These two symplectite textures record the evolution of metastable phases within reduced magmatic conditions in extraterrestrial environments.

¹Adriana Pisarčíková, ¹Jiří Borovička, ²Pavol Matlovič
Icarus (in Press)
Open Access Link to Article [DOI: 10.1016/j.icarus.2026.117327]
¹Astronomical Institute of the Czech Academy of Sciences, Fričova 298, Ondřejov, 25165, Czech Republic
²Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava, Mlynská dolina, 84248 Bratislava, Slovakia
Copyright Elsevier

Laboratory simulations of meteor ablation provide a critical quantitative link between the chemical composition of meteoroids and their observed spectral features. In this work, we analyzed high-resolution Echelle spectra (wavelength range 380–780 nm) of 22 diverse meteorites from the dataset presented in our previous work (Matlovič et al., 2024), representing the largest collection of laboratory meteor analogs to date. Using a radiative transfer model assuming local thermodynamic equilibrium (LTE) and accounting for self-absorption in optically thick plasma, we derived plasma parameters and elemental abundances for both major (Fe, Mg, Cr, Mn, Si, Na, Ni, Li, and K) and minor (Co, Cu, and V) species. Comparison with known bulk meteorite compositions allowed us to validate the modeling approach and assess chemical biases resulting from laboratory-induced ablation. Our analysis suggested plasma temperatures between 5220 and 5810 K and revealed systematic discrepancies in the elemental abundances compared to the original chemical composition. Specifically, we observed a significant enhancement of volatile species (Na, K) relative to Fe, accompanied by a depletion of the moderately volatile element Mg, while refractory elements (Al, Ca, Ti) remained undetected in the plasma radiation. These trends are consistent with the equilibrium vaporization model and demonstrate that under the simulated entry conditions ($\sim$12 km s⁻¹ at $\sim$80 km altitude), the ablation process is dominated by incomplete and fractional vaporization. We conclude that while laboratory spectra of plasma from ablated meteorites do not fully reflect the original bulk composition, radiative transfer modeling effectively characterizes the state of the radiating plasma, offering a more robust approach for interpreting compositional properties from meteor observations.

¹Justin I. Simon, ²Rosalind M. G. Armytage
Earth and Planetary Science Letters, 695, 120293
Open Access Link to Article [DOI: 10.1016/j.epsl.2026.120293]
¹Astromaterial Research & Exploration Science, NASA Johnson Space Center, Houston, TX, 77058, USA
²Amentum, NASA Johnson Space Center, 2101 NASA Parkway, Houston, TX, 77058, USA
Copyright Elsevier

Thermal ionization mass spectrometry measurements of non-mass-dependent calcium isotope effects in calcium-aluminum-rich refractory inclusions show resolvable anomalies, both ⁴⁸Ca isotope excesses and deficits, when compared to measured reference materials used to define the normal terrestrial planet composition (ε⁴⁸Ca = 0$\pm$3.52SD ε-unit, part in 10,000, for the ⁴⁸Ca/⁴⁴Ca ratio). For two of the studied inclusions resolvable intra ε⁴⁸Ca heterogeneity also exists. The measured range and heterogeneity of calcium isotope effects represent a vestige of presolar stellar nucleosynthetically distinct carriers contributed to the Solar protoplanetary disk at the time refractory inclusions were forming, representing the earliest record of infall events since molecular cloud collapse. When directly compared to mass-dependent calcium isotope fractionation effects, as well as mass-dependent and non-mass-dependent titanium isotope effects, and moderately refractory element isotopic signatures, a more complete view of how inclusions, and through their compositions, the early Solar System formed. Additionally, the long-debated nature of several common inclusion types, e.g., melilite-mantled coarse-grained Type B’s, can be more clearly understood when evidence from both refractory elements, for a primordial record, and the moderately refractory elements, for late nebular formation events are considered. Collectively, cosmochemical and chronological records contained in refractory inclusions are important because they formed during the early period of Solar System evolution in which the protoplanetary disk began to dissect into distinct radial reservoirs, likely caused by the formation of giant gaseous planets, directly recording reservoirs, processes, and timescales from which building blocks of terrestrial planets emerged.

¹M. A. Ivanova, ^2,3S. N. Britvin, ⁴A. N. Krot, ⁴K. Nagashima, ⁵N. G. Zinovieva
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70234]
¹Vernadsky Institute of Geochemistry of the Russian Academy of Sciences, Moscow, Russia
²Saint-Petersburg State University, St. Petersburg, Russia
³Kola Science Center, Russian Academy of Sciences, Apatity, Russia
⁴Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, Hawaii, USA
⁵M. V. Lomonosov Moscow State University, Moscow, Russia
Published by arrangement with John Wiley & Sons

We describe here zeolites and zeolite-like phases in Ca,Al-inclusions (CAIs) from Kaidun microbreccia and Northwest Africa (NWA) 3118 (CV3) chondrite studied using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), secondary ion mass spectrometry (SIMS), Fourier transform infrared (FT-IR) spectroscopy, and single-crystal X-ray diffraction (SCXRD). Large (~4–8 μm in size) fragments of a coarse-grained igneous type B CAI from Kaidun consist of melilite (Åk_35–75), anorthite, magnesian spinel (<1 wt% FeO), and Al,Ti-diopside (in wt%, TiO₂ 4–18, Al₂O₃ 16–22); perovskite, hibonite, and Fe,Ni-metal are minor. The CAI experienced aqueous alteration that resulted in replacement of melilite by the calcite + apophyllite [KCa₄ (Si₈O₂₀) (OH,F)·8H₂O] + zeolites [natrolite (Na₂Al₂Si₃O₁₀·2H₂O)] and phillipsite-Na [(Na,K,Ca_0.5)_4–7 (Al_4–7Si₁₂₋₉O₃₂)·12H₂O] assemblage previously unreported in meteorites. Oxygen isotopic composition of calcite is similar to that in CR chondrites (Δ¹⁷O ~2‰, δ¹⁸O ~41‰). Phillipsite and natrolite have Δ¹⁷O close to that of calcite; the lack of proper SIMS standards for these minerals does not allow us to constrain their δ¹⁸O values. These data and textural observations suggest co-precipitation of calcite and zeolites. Calcite–zeolite assemblages are commonly observed in terrestrial rocks that experienced aqueous alteration in the presence of low-temperature alkaline- and carbonate-rich solutions. We suggest that aqueous alteration and formation of calcite–zeolite–apophyllite assemblage in Kaidun CAI occurred in fractures, cracks, and veins from volatile-rich, alkaline hydrothermal fluids (pH = 8–10) at ~20–150°C. This alteration has little effect on oxygen and aluminum–magnesium isotope systematics of primary minerals in the Kaidun CAI: melilite, spinel, pyroxene, and anorthite have solar-like oxygen isotope compositions: Δ¹⁷O = −22 to −25‰ and show resolvable excess of radiogenic ²⁶Mg corresponding to the inferred initial ²⁶Al/²⁷Al ratio [(²⁶Al/²⁷Al)₀] of (4.97 ± 0.11) × 10⁻⁵ (MSWD = 0.57; δ²⁶Mg*₀ = 0.04 ± 0.05‰). Type C CAI from NWA 3118 consists of melilite (Åk_18–56, 0.1–0.3 wt% Na₂O), anorthite, Al,Ti-diopside (in wt%, TiO₂ 3–5, Al₂O₃ 16–24), and spinel (up to 3.3 wt% FeO). Melilite and anorthite in the peripheral part of the CAI are replaced by nepheline, sodalite, Na-bearing plagioclase, and hedenbergite. Melilite in the CAI core is replaced by a hydrated silica-rich amorphous phase, which may have been originally a zeolite that subsequently experienced structural and compositional changes during thermal metamorphism in the CV parent asteroid.

¹Jiawei Wang, ^1,2Nicole M. Fernandez
Journal of Geophysical Research: Planets, 131, e2025JE009493 Open Access Link to Article [DOI: 10.1029/2025JE009493]
¹Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA
²Department of Earth and Planetary Sciences, ETH Zürich, Zürich, Switzerland
Published by rrangement with John Wiley & Sons

Oxidized clays and the widespread Al/Si-over-Fe/Mg stratigraphy on Mars imply prolonged water-rock interactions and efficient oxidative weathering despite the largely anoxic conditions of Early Mars when most deposits formed during the climate optimum. Oxychlorine species are now known to be common on Mars, and laboratory kinetics show that chlorate oxidizes Fe(II) orders of magnitude faster than O2$$ at low temperatures, motivating a chlorate-centered oxidative weathering framework. We develop a 1-D reactive transport model that explicitly includes Fe(II) oxidation by chlorate to evaluate whether low-temperature alteration of basalt can produce oxidized Fe(III)-rich smectites (nontronite) and associated weathering-derived minerals commonly observed on Mars. Model simulations span oxidant supply (chlorate 1⁢0−10$$–1⁢0−3 M$$; oxygen partial pressure (p⁢O2$$, 1⁢0−5$$–0.21 bar), climate (0–25 °C$$; 30–800 m⁢m y⁢r−1$$), and parent basalt mineralogy. Across this space, only saponite, nontronite, kaolinite, and amorphous silica consistently formed. Dissolved chlorate on the order of 1⁢0−5$$–1⁢0−4 M$$ reproduces the canonical Al/Si cap over Fe/Mg-smectites within ∼200 kyr and builds clay-bearing intervals approaching 100 m. Clay-bearing unit accumulation is nonlinear, with most deposition occurring in the early stages of oxidative weathering, highlighting limitations of constant net-rate assumptions for long-term thickness. An intermediate climate window ( ∼10$$–15 °C$$; 50–100 m⁢m y⁢r−1$$) preserves thick sections with an Al-rich cap. Certain clay phases are sensitive to parent basalt mineralogy (plagioclase favors kaolinite; olivine/pyroxene favor saponite), whereas nontronite reflects oxidant capacity and amorphous silica marks cool–dry conditions. These findings provide a testable chlorate-driven framework that reconciles oxidized clays under anoxic conditions and links stratigraphy to redox, climate, and bedrock composition.

¹Joanna V. Egan, ^1,2Wuhu Feng, ¹Alexander D. James, ³James Manners, ^1,4Daniel R. Marsh, ⁵Sébastien Lebonnois, ⁶Franck Lefèvre, ⁷Aurélien Stolzenbach, ¹John M. C. Plane
Journal of Geophysical Research: Planets, 131, e2025JE009634 Open Access Link to Article [DOI: 10.1029/2025JE009634]
¹School of Chemistry, University of Leeds, Leeds, UK
²NCAS, University of Leeds, Leeds, UK
³Met Office, Exeter, UK
⁴School of Physics and Astronomy, University of Leeds, Leeds, UK
⁵Laboratoire de Météorologie Dynamique, Sorbonne Université, ENS, PSL Research University, École Polytechnique, Institut Polytechnique de Paris, CNRS, Paris, France
⁶LATMOS, Sorbonne Université, UVSQ Paris-Saclay, CNRS, Paris, France
⁷Instituto de Astrofisica de Andalucia (IAA/CSIC), Granada, Spain
Published by arrangement with John Wiley & Sons

Near-ultraviolet imaging of the planet Venus reveals inhomogeneous absorption features in the otherwise bright clouds. This absorption has been studied for nearly 100 years, but identification of the near-UV absorber remains one of the largest open questions in Venusian research. Based on a multiple scattering radiative transfer model, the observed absorption between 300 and 600 nm can be produced by 1.0–1.2 wt% ferric chloride (FeCl₃) in the mode 1 (∼0.2 μm radius) sulfuric acid cloud droplets—less than the in-cloud iron mass loading measured during the Venera-12 mission. We present a novel chemical network within a global chemistry-climate model, which provides the required source of FeCl₃ in the upper cloud region from the reaction of Fe-containing molecules, produced by the ablation of cosmic dust particles, with atmospheric HCl. A residence lifetime of ∼3,000 years is required to provide sufficient optical absorption from a purely meteoric source of FeCl₃.

¹Shounak Dutta, ¹Paul D. Asimow, ¹Kenneth A. Farley, ²Arya Udry, ³Nicholas Randazzo, ⁴Kenneth H. Williford
Journal of Geophysical Research: Planets, 131, e2026JE009746
Link to Article [DOI: 10.1029/2026JE009746]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Department of Geoscience, University of Nevada, Las Vegas, NV, USA
³University of Alberta, Edmonton, AB, Canada
⁴Blue Marble Space Institute of Science, Seattle, WA, USA
Published by arrangement with John Wiley & Sons

The Margin Unit, explored by the Mars 2020 Perseverance rover in Jezero crater, is a distinctolivine‐rich lithology whose origin has remained unresolved due to extensive alteration and lack of preservedprimary textures. While hypotheses for its formation range from sedimentary to igneous, recent geochemicaldata allow for quantitative testing of these scenarios. To test the igneous hypothesis, we applied Markov ChainMonte Carlo simulations with MELTS thermodynamic modeling to assess whether the observed olivine andspinel compositions in the Margin Unit are consistent with igneous fractional crystallization. Our simulationsreproduce the observed systematic increase in spinel TiO2/Cr2O3 with decreasing olivine forsterite content, apattern difficult to reconcile with sedimentary mixing processes, providing strong evidence for an igneousorigin for the Margin Unit. Furthermore, continuing evolution of the same magma leads to coexisting olivineand clinopyroxene compositions that suggest a genetic link between the Margin Unit and the crater floor olivine‐rich unit, Séítah, pointing toward the existence of an extensive igneous complex within Jezero crater. Modeledmagma compositions for the Margin Unit are comparable to the parental melt compositions of the chassignitegroup of Martian meteorites, implying conditions necessary to produce chassignite‐like melts were alreadyestablished early in Noachian Mars

^1,2E. L. Cardarelli, ³T. M. Present, ⁴P. M. Vasconcelos, ⁵L. C. Kah, ^3,6C. Swindle, ³S. Bhattacharjee, ³K. Farley
Journal of Geophysical Research: Planets, 131, e2026JE009660 Open Access
Link to Article [DOI: 10.1029/2026JE009660]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA, USA
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
³Division of Geologic and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
⁴The University of Queensland, Brisbane, QLD, Australia
⁵Department of Earth, Environmental and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
⁶Department of Materials Science and Engineering, University of California, Los Angeles, CA, USA
Published by arrangement with John Wiley & Sons

Magnesite (MgCO₃) is a magnesium (Mg) carbonate mineral that records the aqueous environmental conditions of its formation. On Earth, magnesite forms in metamorphic, diagenetic or pedogenic environments, and distinguishing between these environments is critical for understanding the fluid chemistry during magnesite precipitation. Mg carbonates have been observed across the Nili Fossae region on Mars and in Jezero crater by orbital spectroscopy as well as in situ by the Perseverance rover. Rover acquired core samples with Mg carbonates may provide constraints on the chemical conditions of the ancient aqueous environments of Jezero crater, and may also be an important target for the preservation of potential biosignatures. This work explores magnesite phases found in Vertisols of the Kunwarara Mine, Australia, as a potential analog environment for magnesite on Mars. We document the principal microtextures, mineralogical context, and elemental compositions. We investigate the processes involved in the formation and diagenesis of magnesite nodules and a magnecrete. Kunwarara hosted magnesite shows complex textural relationships at the outcrop scale, and these relationships extend down to the nanoscale in samples that were collected along a depth profile. By characterizing textural and chemical variations in magnesite at different scales, this work reveals a continuum between diagenetic and pedogenic magnesites. It illustrates that diagenetic reactions produce magnesite from ascending Mg²⁺-rich groundwater interacting with detrital phases; groundwater interaction with descending meteoric solutions result in the conversion of magnesite into authigenic dolomite. Overall, this work shows how the superposition of textures and elemental compositions permits reconstruction of pedogenic processes leading to magnesite authigenesis.

^1,2Xiaojia Zeng, ³Chenkun Sun, ²Mingchao Xiong, ^1,2Xiongyao Li
Journal of Geophysical Research: Planets, 131, e2026JE009807 Link to Article [DOI: 10.1029/2026JE009807]
¹State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
Published by arrangement with John Wiley & Sons

Hypervelocity impacts from micrometeorites or asteroids are a dominant long‐term geologicalprocess that modifies the mineralogical and elemental components of surface regolith on the Moon and otherairless planetary bodies. However, the pathways by which impacts drive elemental redistribution on the Moonremain poorly understood. Here, we report the discovery of thousands of chromite (FeCr2O4) nanoparticlesdeposited on a space‐weathered olivine fragment from Chang’e

¹Yoshio Kono (>10)

Journal of Geophysical Research: Planets, 131 e2026JE009944 Link to Article [DOI: 10.1029/2026JE009944]
¹Department of Physics and Astronomy, Kwansei Gakuin University, Sanda, Japan
Published by arrangement with John Wiley & Sons

Oxidation state of magma ocean is one of the most important factors, which influence its nature and dynamics. Since iron is the most abundant redox-sensitive element, understanding the effect of ferrous (Fe²⁺) and ferric (Fe³⁺) iron on the physical properties and structure of peridotite melts are fundamental to discuss geophysical and geochemical evolutions of magma ocean. In this study, we investigate the viscosity of Fe³⁺-bearing peridotitic melts under Ar gas environment by utilizing an electrostatic levitation furnace at the International Space Station. The results show strong increase of the viscosity of the Fe³⁺-bearing peridotitic melts with increasing iron content, which is in contrast to previous reports of lower viscosities of iron-abundant peridotitic melts than iron-poor peridotitic melts under reduced environment. Our structural investigations show that Fe³⁺ causes polymerization of melt structure with increasing iron content, while Fe²⁺-dominant peridotitic melts under reduced environment show almost no change in the melt structure. These results indicate that polymerization of melt structure by Fe³⁺ strongly increases the viscosity of peridotitic melt, while simple replacement of Mg²⁺ with Fe²⁺ decreases the viscosity of peridotitic melt. Since deep magma ocean is considered to be enriched in Fe³⁺, due to disproportionation reaction to form metallic iron and Fe³⁺ at high pressures, strong increase of the viscosity of peridotitic melt by the formation of Fe³⁺ would be important to discuss nature and dynamics of magmas at deep planetary interiors, such as formation and stability of the basal magma ocean at the core-mantle boundary in Mars.