^1,2X. Zhu,¹Y. Ye,^2,3R. Caracas
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008839]
¹State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan, China
²Institut de Physique du Globe de Paris, CNRS, Université Paris Cité, Paris, France
³The Research Center of the University of Bucharest, Bucharest, Romania
Published by arrangement with John Wiley & Sons

The formation and evolution of rocky planets such as the Earth are marked by the heavy bombardments that dominated the first parts of the accretions. The outcomes of the large and giant impacts depend on the critical points and liquid-vapor equilibria of the constituent materials. Several determinations of the positions of the critical points have been conducted in the last few years, but they have mainly focused on systems devoid of volatiles. Here, we study, for the first time, a volatile-rich ubiquitous model mineral, phlogopite. For this, we employ ab initio molecular dynamics simulations. Its critical point is constrained in the 0.40–0.68 g/cm3 density range and 5,000–5,500 K temperature range. This shows that adding volatiles decreases the critical temperature of silicates while having a smaller effect on the critical density. The vapor phase that forms under cooling from the supercritical state is dominated by hydrogen, present in the form of H2O, H, OH, with oxygen and various F-bearing phases coming next. Our simulations show that up to 93% of the total hydrogen is retained in the silicate melt. Our results suggest that early magma oceans must have been hydrated. In particular for the Moon’s history, even if catastrophic dehydrogenation occurred during the cooling of the lunar magma ocean, the amount of water incorporated during its formation could have been sufficient to explain the amounts of water found today in the last lunar samples.

¹W. H. Farrand et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008645]
¹Space Science Institute, Boulder, CO, USA
Published by arrangement with John Wiley & Sons

The Mars Science Laboratory rover, Curiosity, has been examining strata from a period of Martian history where extensive clay mineral formation transitioned to sulfate mineral formation. This mineralogic change corresponds to a change from a wetter to a more arid climate. Among the tools used by Curiosity to study the rocks that recorded this transition is the multispectral capability of its Mast Camera (Mastcam). The Mastcam filter wheel, in combination with its Bayer Pattern filter focal plane array has provided multispectral scenes recorded in 12 spectral bands over the 445–1,013 nm spectral range. Here, Mastcam multispectral results from the rover’s exploration of predominantly sulfate-bearing strata that bracket a distinct dark-toned resistant stratigraphic marker unit, now referred to as the Amapari Marker Band (AMB), are presented in association with supporting information from some of Curiosity’s other instruments. Using an agglomerative hierarchical clustering approach, six spectral classes were derived. These classes included three stratigraphic classes plus a class indicating more intense diagenetic alteration and classes of dark-toned float rocks and a set of Fe-Ni meteorites. These spectral classes were compared to the spectra of analogous terrestrial materials. Among the observations, a distinct tonal and color unit was observed directly below the Amapari Marker Band. Several lines of evidence suggest this narrow interval is an alteration horizon. The alteration could have resulted from diagenesis, exposure as a weathering surface, or from introduction of water associated with the deposition of the lower AMB.

¹T.A. Williams, ¹S.W. Parman, ¹A.E. Saal, ²A.J. Akey, ²J.A. Gardener, ³R.C. Ogliore
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116607]
¹Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, United States of America
²Center for Nanoscale Systems, Harvard University, Cambridge, MA, United States of America
³Department of Physics, Washington University in St. Louis, St. Louis, MO, United States of America
Copyright Elsevier

Lunar pyroclastic glass beads preserve a record of physical and chemical conditions within volcanic gas clouds in the form of nanoscale minerals vapour-deposited onto their surfaces. However, the scale of these mineral deposits – less than 100 nm – has presented challenges for detailed analysis. Using SEM, TEM, APT, and NanoSIMS, we analysed pristine glass beads from Apollo drive tube 74,001 and found a sequence of sulfide deposition that directly evidences lunar gas cloud evolution. The deposits are predominantly micromound structures of nanopolycrystalline sphalerite ((Zn,Fe)S), with iron enrichment at the bead-micromound interface. Thermochemical modelling indicates that hydrogen and sulfur were major elements within the volcanic plume and ties the iron gradient to decreasing gas pressure during deposition. This pressure drop may also be consistent with our observed trend of potential
depletion. Finally, Apollo 1,774,220 orange beads, deposited higher in the Shorty Crater sequence, appear to lack abundant ZnS nanocrystals (Liu and Ma, 2024a), suggesting a change in vapour deposition between black- and orange-glass bead deposition. Together, our results suggest a change in eruption style over the course of a pyroclastic volcanic eruption in the Taurus-Littrow Valley.

¹Piers Koefoed, ¹Kun Wang (王昆)
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.04.012]
¹Department of Earth, Environmental, and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
Copyright Elsevier

Understanding chondrule formation processes has been a major focus of the cosmochemistry community for many decades. In order to help further this understanding, here we apply high-precision K isotope analyses to chondrule fractions from the four Antarctic unequilibrated ordinary chondrites of QUE 97008 (L3.05), MET 00452 (L(LL)3.05), GRO 95658 (LL3.3), and GRO 95539 (LL3.2). The K isotope ratios of the chondrules fractions from all four of these samples lie within the range of −2.20 ‰ to 0.14 ‰ δ41K, with QUE 97008, MET 00452, GRO 95658, and GRO 95539 showing chondrule fraction δ41K ranges of −1.54 to 0.14 ‰, −0.76 to −0.28 ‰, −2.20 to −1.23 ‰, and −1.30 to −0.84 ‰, respectively. Overall, no strong correlations between K isotope ratio and K concentration are observed among the chondrule fractions for any of the four chondrites. Additionally, unlike what was seen previously for the LL4 Hamlet, no correlation between chondrule mass and K isotope ratio was observed. In conjunction with previous studies, the data here suggest that a combination of secondary parent body processes and nebular processes involved in chondrule formation are the dominant controls on the K isotope systematics of the chondrules from unequilibrated ordinary chondrites. The effects of secondary parent body processing vary significantly from chondrule to chondrule, however, the dominant effect is the migration of K from the K rich matrix to the K poor chondrules. As such, parent body alteration partially overprinted and disturbed the initial chondrule K compositions to various degrees. Nevertheless, even with the effects of parent body processing, the key observation that the vast majority of the chondrule fractions show δ41K values lighter than, or equal to, their respective matrix and bulk compositions is best explained by these chondrules experiencing incomplete condensation in the solar nebula. This aligns with K isotope observations made for the carbonaceous chondrites where the matrix-dominated CI chondrites are enriched in heavier K isotopes and the chondrule-rich carbonaceous chondrites are enriched in lighter K isotopes. The K isotopes of individual chondrules in this study suggest that chondrules from ordinary chondrites were also formed via incomplete condensation from a supersaturated medium, agreeing with the previous conclusion drawn for carbonaceous chondrules. This means both CC and OC chondrules likely experienced incomplete condensation, making this chondrule formation process ubiquitous and widespread throughout both the inner and outer regions of early solar nebula.

^1,2,3Liam D. Peterson,³Megan E. Newcombe,⁴Conel M.O’D. Alexander,⁴Jianhua Wang,^1,2,5Sune G. Nielsen
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.04.009]
¹Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02540, United States
²NIRVANA Labs, Woods Hole Oceanographic Institution, Woods Hole, MA 02540, United States
³Department of Geology, University of Maryland, College Park, MD 20740, United States
⁴Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015, United States
⁵CRPG, CNRS, Université de Lorraine, 15 rue Notre Dame des Pauvres, 54501 Vandoeuvre lès Nancy, France
Copyright Elsevier

Erg Cech 002 (EC 002) is an andesitic achondrite, the earliest formed achondrite identified to date, and is a rare sample of primary melts that formed crusts on the first generation(s) of planetesimals. Given that EC 002 represents a primary or primitive melt and that H and F are incompatible during silicate partial melting, EC 002 may be a H- and F-rich material relative to previously studied achondrites. We measured the H2O (total H quantified as H2O) and F contents of low-Ca pyroxene xenocrysts (∼4– 12 µg/g H2O; <0.5 µg/g F), groundmass augite (∼5 – 10 µg/g H2O; <2.2 µg/g F), albitic feldspar (∼2– 5 µg/g H2O; <0.5 µg/g F), and a silica-rich phase (∼28– 30 µg/g H2O; ∼0.7– 2.5 µg/g F) in EC 002 by Nanoscale Secondary Ion Mass Spectrometry. We use a single-stage equilibrium batch melting model to provide a first-order reconstruction of the EC 002 parent body H2O (∼7– 200 µg/g H2O) and F (∼0.44– 2.4 µg/g F) contents, which are depleted relative to chondrites and the bulk Earth. This requires the first generation(s) of planetesimals to have either accreted from volatile-poor materials or undergone extensive volatile loss, supporting the idea that Earth acquired its H2O budget from thermally primitive materials.

¹M. E. Varela,²J. Roszjar,³P. Sylvester,^1,4L. Garcia
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14360]
¹Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE), CONICET-San Juan, San Juan, Argentina
²Department of Mineralogy and Petrography, Natural History Museum Vienna, Vienna, Austria
³Department of Geosciences, Texas Tech University, Lubbock, Texas, USA
⁴Instituto de Mecánica Aplicada, Universidad Nacional de San Juan, San Juan, Argentina
Published by arrangement with John Wiley & Sons

Barred olivine (BO) chondrules are present in ordinary and carbonaceous chondrites. We focus on the bulk major and trace element abundance composition of BO chondrules from carbonaceous, unequilibrated ordinary, and Rumuruti chondrites. Their bulk Fe/(FeO + MgO) wt% content versus the FeO wt% in olivine was used to divide these objects into FeO-poor and FeO-rich BO chondrules. The trace element content of bulk BO chondrules reveals the absence of fractionation among the abundances of elements having different geochemical behavior (e.g. Yb and [La-Ce]). This points to the predominance of a cosmochemical (e.g. gas/liquid or gas/solid condensation) instead of a geochemical process determining their elemental abundances. In addition, their bulk trace element content provides evidence for the physicochemical conditions that prevailed in the solar nebula during their formation. In general, such nebular regions are governed by local redox variations coupled with overall falling temperatures. The bulk chemical composition of the studied BO objects (e.g., Mg/Si bulk) suggests a time scale in which FeO-poor BO chondrules formed first in a chondrule-forming region rich in refractory trace elements. The progressive removal of refractory phases (e.g., hibonite, fassaite, melilite) led to a nebular reservoir depleted in the very refractory elements (e.g., Zr and Y) in which the rare earth elements (REEs) tend to reach equilibrium with the chondritic reservoir. From such a reservoir, the FeO-rich BO chondrules could have formed and were subsequently processed by metasomatic exchange reactions that equilibrated their moderately volatile V and Cr around chondritic values. The observed chemical variations are only possible if the studied BO chondrules behave as open systems exchanging elements with the cooling vapor. The inferred local redox variations coupled with overall falling temperatures could have taken place during the evolution of a single heterogeneous nebular reservoir in which Fe-poor and FeO-rich BO chondrules formed.

^1,2Yash Srivastava et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14357]
¹Planetary Science Division, Physical Research Laboratory, Ahmedabad, India
²Scripps Institution of Oceanography, University of California San Diego, San Diego, California, USA
Published by arrangement with John Wiley & Sons

Aubrites are rare meteorites from highly reduced differentiated parent bodies. The Rantila meteorite was recovered soon after falling on 17 August 2022 at Rantila and Ravel villages in Gujarat state, India. We report the petrography, mineralogy, chemical composition, oxygen- and chromium-isotope compositions, along with reflectance spectroscopy, all showing that Rantila is an aubrite. Coarse enstatite and diopside grains constitute the main mass of Rantila, while mm-wide fracture domains pervade the coarse enstatites. In the fractures, comminuted enstatite, diopside blebs, olivine, a plagioclase–silica assemblage, sulfides, and metals occur. Rantila consists of enstatite (>85 vol%), diopside (~8 vol%), forsterite, albite, and silica along with various sulfides and Fe-Ni alloys. The concentration of rare earth elements is ~1–2 × CI, consistent with main group aubrites. Noble gas and nitrogen isotopic analyses reveal young exposure ages (13.81 ± 6.47 Ma), a heterogeneous nitrogen isotopic composition, and a major K-Ar resetting event around 3.2 ± 0.4 Ga in the parent body of Rantila. The bulk oxygen isotope values are within the range of aubrites. The chromium isotopic values of Rantila are consistent with main group aubrites. The mineral assemblages, texture, and crystallization modeling suggest that Rantila had an igneous origin. The mineral assemblages in fractures indicate the involvement of external melt possibly during an impact-fracturing event, which aligns well with the heterogeneous N isotopic composition. Additionally, Rantila shows a wider range of oxygen isotopes than other aubrites suggesting some extent of O isotopic heterogeneity, likely stemming from exogenous processes. The variation in intra-sample bulk O and N isotope values implies inherent heterogeneity within the main group aubrites, potentially caused by late-stage impact contamination.

¹Brendan A. Anzures,^1,2Kathleen E. Vander Kaaden,³Francis M. McCubbin,^1,4Richard L. Rowland, II,^1,4Gordon M. Moore,¹Kelsey Prissel,³Richard V. Morris,⁵Rachel L. Klima,⁵Karen R. Stockstill-Cahill,⁶David G. Agresti
American Mineralogist 110, 570-581 Open Access Link to Article [https://doi.org/10.2138/am-2024-9400]
¹Jacobs, NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
²NASA Headquarters, Mary W. Jackson Building, Washington, D.C. 20546, U.S.A.
³ARES NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
⁴Los Alamos National Laboratory, Los Alamos, New Mexico 87545, U.S.A.
⁵The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, U.S.A.
⁶Department of Physics, University of Alabama at Birmingham, 902 14th Street South, Birmingham, Alabama 35294, U.S.A.
Copyright: The Mineralogical Society of America

Results from X-ray remote sensing aboard NASA’s MErcury Surface Space ENvironment GEochemistry and Ranging (MESSENGER) spacecraft have demonstrated that Mercury has a low, but measurable, concentration of Fe on its surface. However, ultraviolet to near-infrared spectroscopic measurements of the mercurian surface do not show the 1 μm absorption band characteristic of ferromagnesian silicates. This observation is consistent across multiple Fe-bearing terranes with a range of ages, suggesting the Fe present on Mercury’s surface may not be stored within silicate phases. To further constrain the possible mineralogy and composition of Fe-bearing phases on Mercury, we used various spectroscopic techniques to characterize synthetic olivine with minor amounts of Fe (i.e., Fo99.62–Fo99.99) and more Fe-rich natural olivines. Our results indicate that the distinctive 1 μm absorption band of olivine is detectable in reflectance spectra of olivine at a concentration as low as 0.03 wt% FeO and 0.01 wt% in continuum removed data. Additionally, MESSENGER’s lack of a 1 μm absorption, taking into account Mercury Dual Imaging System (MDIS)’s limited spectral resolution and Mercury Atmospheric and Surface Composition Spectrometer (MASCS)’s high signal-to-noise ratio, suggests there is <0.38 wt%, and likely <0.01 wt%, FeO on the surface of Mercury. Because the 1 μm band is not observed in surface spectra, these results indicate that the Fe observed on the surface of Mercury is not bound in an olivine structure. Rather, we posit that Fe is present as nano-phase and macroscopic Fe-rich metal or Fe-sulfide that formed as a result of space weathering and igneous smelting processes. Looking forward to ESA/JAXA’s BepiColombo mission that has a planned Mercury orbit arrival time in December 2025, Mercury Radiometer and Thermal Infrared Imaging Spectrometer (MERTIS) mid-infrared spectra should provide a mineralogical detection or absence of olivine where MIR spectral features are still present even in synthetic olivines with minor amounts of Fe (Fo99.99).

^1,2Roberto Borriello,³Fahui Xiong,⁴Chi Ma,¹Sofia Lorenzon,¹Enrico Mugnaioli,⁵Jingsui Yang,⁶Xiangzhen Xu,⁷Edward S. Grew
American Mineralogist 110, 630-642 Link to Article [https://doi.org/10.2138/am-2024-9362]
¹Department of Earth Sciences, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy
²Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Via Torino 155, 30172 Mestre (VE), Italy
³Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep-Earth Dynamics of Ministry of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
⁵School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China
⁶Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep-Earth Dynamics of Ministry of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
⁷School of Earth and Climate Sciences, University of Maine, Orono, Maine 04469, U.S.A.
Copyright: The Mineralogical Society of America

^1,2Ziliang Jin,^3,4,5Tong Hou,^1,2Meng-Hua Zhu,^6,7Yishen Zhang,⁶Olivier Namur
American Mineralogist 110, 560–569 Link to Article [https://doi.org/10.2138/am-2024-9448]
¹State Key Laboratory of Lunar and Planetary Science, Macau University of Science and Technology, Taipa, 999078, Macao, China
²CNSA Macau Center for Space Exploration and Science, Taipa 999078, Macau, China
³State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, 100083 Beijing, China
⁴Key Laboratory of Intraplate Volcanoes and Earthquakes (China University of Geosciences, Beijing), Ministry of Education, Beijing 100083, China
⁵Institute of Mineralogy, Leibniz Universität Hannover, Callinstr. 3, 30167, Hannover, Germany
⁶Department of Earth and Environmental Sciences, KU Leuven, 3000, Leuven, Belgium
⁷Department of Earth, Environmental and Planetary Sciences, Rice University, 6100 Main Street, MS 126, Houston, Texas 77005, U.S.A.
Copyright: The Mineralogical Society of America

This study investigates silicate liquid immiscibility (SLI) microstructures in the Chang’E-5 (CE-5) lunar ferrobasalt sample, the youngest recovered mare basalt (ca. ∼2.0 Ga). Employing advanced high-resolution imaging techniques and chemical analysis, we examined a subophitic fragment, revealing two distinct types of microstructures indicative of multi-stage SLI events. The first type is observed in the mesostasis pockets and exhibits both “sieve” and “maze” textures, where the Si-K-rich glassy phases are interconnected with Fe-rich minerals, e.g., fayalite. This type of microstructure, similar to previous observations in Apollo and Luna samples, is the product of a stable SLI event. The second type is characterized by K-free but high-Si melt inclusions occurring as emulsions in the rims of plagioclase. The entrapment of these emulsions followed a metastable SLI event, with the Fe-rich liquids serving as precursors to subsequent stable SLI processes. Additionally, the Fe-rich droplets within the emulsions underwent coarsening via Ostwald ripening, a phenomenon in which smaller particles in solution dissolve and deposit on larger particles. Our simulation of this coarsening process suggests a duration of at least 15–32 days for the SLI processes, alongside a slow cooling rate (<0.3 °C/h) of the late-stage CE-5 lava. We propose that metastable SLI may have influenced the effusive signature of the CE-5 lava flow during its late-stage evolution. The metastable SLI process can potentially lead to the formation of various phases during the late-stage evolution of lunar ferrobasaltic magmas, thereby contributing to the diversity of lunar rock types.