¹D. Rezes,²I. Gyollai,³S. Biri,⁴K. Fintor,³Z. Juhász,³R. Rácz,³B. Sulik,^2,5M. Szabó,^1,5Á. Kereszturi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70038]
¹Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
²Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, HUN-REN, Budapest, Hungary
³Institute for Nuclear Research Debrecen, HUN-REN, Debrecen, Hungary
⁴Department of Geology, University of Szeged, Szeged, Hungary
⁵MTA Centre of Excellence Budapest, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
Published by arrangement with John Wiley & Sons

This paper presents the results of proton irradiation actions of three meteorites which were studied by LV-SEM, Raman spectroscopy, and FTIR spectroscopy methods, both before and after the artificial irradiations. The three samples are the Dhofar (Dho) 007 eucrite, the Northwest Africa (NWA) 4560 LL3.2, and the NWA 5838 H6 chondrite meteorites, which were irradiated by 1 keV average solar wind protons using the ECR ion source at ATOMKI with 1017 and 1019 ions cm−2 fluence values. According to FTIR spectra, the first irradiation induced metastable alteration, and after the second irradiation, crystals organized into more stable phases. In the Dho 007 sample, the pyroxene shows a positive peak shift and FWHM change after the first irradiation, with decreased intensity of spectra. After the second irradiation, the peak position and FWHM decreased but showed an increase in comparison with the state before the irradiation in the FTIR spectra. The minor band near 620 cm−1 disappeared after the irradiations in the FTIR spectra; however, the Raman spectra do not show the disappearance of minor bands. The olivine (in NWA 4560 and NWA 5838) and pyroxene (in Dho 007) showed negative peak shifts indicating escape of Mg2+ ions from the crystal lattice, together with positive peak shifts and increase of FWHM indicating amorphization of the crystal structure. Considering band shapes and intensities, both FTIR and Raman spectra showed decreasing intensity after the first irradiation, with possible metastable alteration. However, the spectra after the second irradiation show a moderate increase in FWHM change, which indicates a change in the crystal lattice. In the FTIR spectra, the minor band at 620 cm−1 disappeared in the case of pyroxene.

¹Qian Fang,²Yan Li,¹Hongrui Ding,¹Liao Yang,¹Hanlie Hong,¹Zhong-Qiang Chen,¹Anbei Deng,¹Qile Geng,²Anhuai Lu
American Mineralogist 110,1343-1360 Link to Article [https://doi.org/10.2138/am-2024-9585]
¹State Key Laboratory of Geomicrobiology and Environmental Changes, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
²School of Earth and Space Sciences, Peking University, Beijing 100871, China
Copyright: The Mineralogical Society of America

Rock varnish is widely distributed across Earth’s various climatic zones, especially prevalent in arid environments similar to Mars. Its potential presence on Mars has made it a significant Mars analog for planetary research. The primary components of rock varnish are clay minerals and iron-manganese oxyhydroxides, with clay minerals possibly playing a crucial role in the enrichment of iron and manganese. However, there has been scarce in-depth and detailed research on these clay minerals within rock varnish. To better understand the formation and transformation mechanisms, as well as the influencing factors of clay minerals in rock varnish, we conducted X-ray diffraction (XRD) analyses on clay minerals isolated from rock varnish samples collected across different climatic regions in China. Additionally, in situ visible to near-infrared spectroscopy (Vis-NIR), scanning electron microscopy (SEM), and focused ion beam high-resolution transmission electron microscopy (FIB-HRTEM) were performed on the rock varnish samples. The results revealed the presence of illite in all rock varnish samples, while the selective occurrence of other clay minerals was closely correlated with climatic backgrounds. Furthermore, the crystallinity of illite was significantly influenced by climatic conditions. Illite found in rock varnish existed as both detrital and authigenic forms. Generally, the detrital illite in rock varnish was thicker than the nanometer-scale authigenic illite and exhibited distinct differences in chemical composition (e.g., Si/Al, K/Al ratios) and nanoscale morphology. In many cases, the possible transformation of illite to chlorite was observed, either internally within illite particles or through the formation of regular or irregular interstratified structures between illite and chlorite. Both interlayer brucitization and talc brucitization mechanisms may be involved in the chloritization (brucitization) of illite in rock varnish. Such transformations are generally uncommon in surface environments and are more frequently associated with low-grade metamorphism, suggesting that the environment at the illuminated rock surfaces, akin to metamorphic conditions, might provide the energy needed for these reactions. Considering the strong solar irradiance characteristic of Mars and its abundance of Mg- and Fe-rich rocks, it is plausible to expect the continued occurrence of chloritization on the martian surface and even within martian rock varnish. Our findings are significant for better understanding the formation and transformation of clay minerals on the martian surface and martian rock varnish, and climate-controlled water-rock interactions on Mars.

^1,2Riley Havel,^1,2Daniel E. Ibarra,³Rainer Bartoschewitz,¹Gerrit Budde
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70039]
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, USA
²The Institute at Brown for Environment and Society, Brown University, Providence, Rhode Island, USA
³Bartoschewitz Meteorite Laboratory, Gifhorn, Germany
Published by arrangement with John Wiley & Sons

Triple oxygen isotope analyses of meteorites are a fundamental tool for classifying meteorites and investigating early solar system processes. However, its utility can be significantly compromised by terrestrial oxygen contamination during weathering processes on Earth’s surface. Aiming to restore the original bulk oxygen isotope composition of meteorites through the removal of terrestrial weathering products, leaching procedures with hydrochloric acid (HCl) or ethanolamine thioglycollate (EATG) are often employed, but their effects remain poorly understood. Therefore, here we obtained high-precision triple oxygen isotope data for a comprehensive set of meteorites to systematically evaluate the efficacy and consequences of these leaching methods as a function of meteorite group, weathering grade, petrologic type, and find/fall location and status. Our data for untreated and leached bulk meteorite powders show that leaching can cause shifts of several permil in 18O/16O and 17O/16O in aqueously altered and pristine chondrites, and lower magnitude shifts in thermally metamorphosed chondrites and achondrites. Though some shifts can be explained by removal of terrestrial weathering products, many suggest the inadvertent removal of indigenous phases. As such, this study highlights the benefits and disadvantages of leaching methods for meteorites, which can be best assessed by analyses of both untreated and HCl/EATG-leached aliquots.

¹I. Criouet, ²S. Bernard, ¹E. Balan, ²F. Baron, ³A. Buch, ¹F. Skouri-Panet, ¹M. Guillaumet, ¹L. Delbes, ¹L. Remusat, ¹J.-C. Viennet
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116789]
¹Muséum National d’Histoire Naturelle, Sorbonne Université, UMR CNRS 7590, Institut de minéralogie, de physique des matériaux et de cosmochimie, Paris, France
²Université de Poitiers, CNRS, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP) UMR, 7285 Poitiers, France
³Laboratoire Génie des Procédés et Matériaux, CentraleSupélec, Gif-sur-Yvette, France
Copyright Elsevier

Clay-rich Martian rocks are considered promising targets in the search for fossilized remains of ancient Martian life. However, the actual influence of the clay mineral compositions in preserving microbial biosignatures remains poorly understood. Here, we explore the biopreservation potential of three pure smectites typically found on Mars and containing Al in their tetrahedral sheets (i.e. a Mg-rich, a Fe-rich and a Al-rich smectite), relying on experiments run using E. coli as a biological analog to simulate hydrothermal alteration scenarios relevant to Mars. The results show that Mg-rich smectites (saponite) are more effective at preserving biomolecules from thermal degradation than Fe-rich and Al-rich smectites (nontronite and beidellite). Plus, in contrast to saponite, neither nontronite nor beidellite appears to significantly trap (and thus preserve) organic compounds within their interlayer spaces. Overall, the present study highlights that both the chemistry and the quantity of organic materials in ancient Martian clay-rich rocks will depend on the compositional nature of smectites initially present.

¹Isabella Pignatelli,²Enrico Mugnaioli,¹Yves Marrocchi,^2,3Luigi Folco
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70031]
¹CRPG UMR 7358 CNRS-UL, Université de Lorraine, Vandœuvre-lès-Nancy Cedex, France
²Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
³CISUP, Center for Instrument Sharing of the University of Pisa, Pisa, Italy
Published by arrangement with John Wiley & Sons

The Nakhla Martian meteorite is known to contain secondary minerals, in particular phyllosilicates, that have recorded the conditions of aqueous alteration of the parent rock. A section of this meteorite was analyzed by transmission electron microscopy to characterize the phyllosilicates in veins and mesostasis. High resolution and electron diffraction, combined with chemical data, suggest the presence of veins in olivine filled by carbonates and hisingerite or hisingerite alone. In the mesostasis, phyllosilicates with composition close to that of ferripyrophyllite were observed in rounded pores within feldspars—these phyllosilicates are associated with areas rich in Si likely due to the presence of amorphous silica. Iron oxides/hydroxides were not found in this study. In addition, for the first time, wadsleyite was observed within the vein margins in olivine. Wadsleyite is evidence of shock metamorphism in Nakhla, whereas the veins result from the decompression after the shock wave passed through due to impact(s). The identification of these secondary minerals constrains the temperature, pH, and redox conditions during the aqueous alteration, underlying that these conditions changed over time. For example, hisingerite forms at T = 120–140°C and ferripyrophyllite at 55–65°C, confirming a progressive temperature decrease when the alteration went forward. The occurrence of these Fe-rich phyllosilicates has also implications on possible past life on Mars: H2-fueled life cannot survive at T > 122°C; thus, it is incompatible with the formation of hisingerite. Life could have been possible only during the last step of aqueous alteration, that is, when the temperature decreased and ferripyrophyllite formed.

^1,2Jonas M. Schneider, ¹Thorsten Kleine
Earth and Planetary Science Letters 669, 119592 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119592]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstraße 1-3, 24148 Kiel, Germany
Copyright Elsevier

The formation of the Moon by a giant impact of an object called Theia onto proto-Earth marks the end of the main stage of Earth’s accretion. However, the timing of this event is controversial, with estimates ranging between ∼50 and ∼220 million years (Ma) after solar system formation. The 87Rb-87Sr system has the potential to resolve this debate, as formation of the Moon resulted in strong fractionation of rubidium from strontium. To better determine the initial 87Sr/86Sr of the Moon, we obtained Rb-Sr isotope data for several lunar ferroan anorthosites, which define an initial 87Sr/86Sr of 0.6990608±0.0000005 (2 s.e.) at 4.360±0.003 Ga. Modeling the pre-giant impact Rb-Sr isotopic evolution of Theia and the proto-Earth reveals that while in the canonical giant impact model no Rb-Sr model age can be determined, all other current impact models yield a Moon formation age of 4.502±0.020 Ga, or 65±20 Ma after solar system formation. When compared to the chronology of lunar samples, this age implies that solidication of the lunar magma ocean took ∼70 Ma, and that the Moon underwent a global re-melting event ∼150 Ma after its formation.

^1,2Madelyn Sita, ²Marvin Osorio, ²Colin Jackson, ³Sujoy Mukhopadhyay
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.08.022]
¹Department of Geology, University of Maryland, 8000 Regents Dr., College Park, 20742, MD, USA
²Department of Earth and Environmental Science, Tulane University, 6823 St. Charles Ave, New Orleans, 70118, LA, USA
³School of Earth and Space Exploration, Arizona State University, 781 E Terrace Mall, Tempe, 85287-6004, AZ, USA
Copyright Elsevier

Ocean island basalts (OIBs) sourced from mantle plumes contain a high ³He/⁴He component, marking the lower mantle as a potential reservoir for primordial, less degassed, material. Some of these same samples have been observed to contain low ¹⁸²W/¹⁸⁴W isotope ratios, which suggest the formation of high ³He/⁴He reservoirs occurred during the early stages of Earth’s formation and point to the core as, potentially, the ultimate source of high ³He/⁴He materials. We developed a computational model to investigate parameters that affect the time-integrated He/(U+Th) ratio present in the core in order to establish the conditions during planetary formation that favor the formation of a high ³He/⁴He reservoir in the core. The parameters investigated are representative of the processes responsible for transporting primordial ³He from the nebular atmosphere and the refractory elements U and Th from the silicate magma ocean into the protoplanets’ differentiated core. The parameters investigated include the radius of the protoplanet, timescale of accretion (), optical opacity of the atmosphere (), amount of Si in the bulk planet (), depth of magma ocean-core equilibration, magma ocean thermal gradient, and the metal-silicate partition coefficient of He (D). The model results, obtained through random sampling of the parameter space, indicated that protoplanets which undergo relatively slow accretion during the lifetime of the solar nebula but still reach sizes larger than 4500 km, protoplanets with optically thin atmospheres, and protoplanets that maintain relatively shallow and cool magma oceans will preferentially develop high ³He/⁴He cores. Overall, Earth’s core could serve as a reservoir for primordial helium, but current parameter space makes the core’s ³He/⁴He ratio highly uncertain.

^1,2A. I. Sheen,^1,2C. K. F. Tirona,^1,2K. T. Tait,^1,2,3L. F. White,^1,2B. C. Hyde,^1,2S. Korchinos
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70028]
¹Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada
²Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
³School of Physical Sciences, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

Olivine is a major constituent in ureilites and commonly defines macroscopic fabric via shape-preferred orientation of elongate grains. In this study, we examined olivine fabric (crystallographic preferred orientation, or CPO) and microstructures in the unbrecciated olivine-pigeonite ureilites Northwest Africa (NWA) 7059 and Nova 018 using electron backscatter diffraction (EBSD) analysis. Point-per-grain orientation data of NWA 7059 indicate a <010> lineation subparallel to grain elongation. Misorientation data of two grains in NWA 7059 indicate dominant activity of (010) [100], (001) [100], (100) [001], and {hk0} [001] slip systems. Nova 018 displays an axial-[010] fabric, with misorientations indicating (010) [001], {hk0} [001] slips, and formation of (010) twist boundaries. Axial-[010] fabric in Nova 018 is consistent with compaction of residual olivine during melt extraction. The <010> lineation in NWA 7059 is unlike typical ureilite fabric and requires a [010] Burgers vector, uncommon in terrestrial samples. Rotational axis analysis of 2°–10° misorientations in olivine shows that the relative proportion of [001] slips and [100] slips in both ureilites are similar to warm-shocked ordinary chondrites, which were deformed at subsolidus temperatures. However, subsolidus deformation temperatures for both studied ureilites are inconsistent with a “hot disruption” model for the ureilite parent body (UPB). The further lack of correlation between 2°–10° misorientation metrics and olivine core Fo content argues against deformation temperature as the main control on olivine slip systems in ureilites. Our findings highlight the use of olivine petrofabric to gain insights into ureilite deformation, as well as complexities in interpreting olivine deformation data with respect to the history of the UPB.

¹A. N. Krot,¹K. Nagashima,²M. I. Petaev,¹E. Dobrică,³C. Ma,⁴B. Jacobsen
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70036]
¹Hawai‘i Institute of Geophysics & Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i, USA
²Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁴Lawrence Livermore National Laboratory, Livermore, California, USA
Published by arrangement with John Wiley & Sons

We report on the mineralogy, petrology, oxygen, and aluminum–magnesium isotopic systematics of the secondary corundum-bearing assemblages in type B CAIs 3529Z and 3529G and fluffy type A (FTA) CAI ALH-2 from Allende (CV > 3.6). In 3529Z and 3529G, 2–5 μm-sized euhedral-to-subhedral corundum grains associate with secondary alumoåkermanite [(Ca,Na)2AlSi2O7], grossular, spinel, grossite, celsian, kushiroite, and wadalite. In ALH-2, 2–5 μm-sized euhedral-to-subhedral corundum grains associate with secondary grossular, nepheline, spinel, and kushiroite. In 3529Z and 3529G, corundum and associated secondary grossite, spinel, alumoåkermanite, grossular, and kushiroite have similar 16O-poor compositions (Δ17O = −2.2 ± 1.5‰); primary spinel is 16O-rich (Δ17O ~ −23‰); Al,Ti-diopside shows a range of Δ17O (from ~ −24‰ to ~ −15‰); anorthite and melilite are 16O-depleted to various degrees (−6.5‰ ≤ Δ17O ≤ −4.5‰ and Δ17O = −2.7 ± 0.8‰, respectively). In ALH-2, corundum shows a range of Δ17O, from ~ −9‰ to ~ −1‰; primary hibonite and spinel are 16O-rich (Δ17O ~ −23‰); melilite and perovskite are 16O-poor (Δ17O = −2.6 ± 1.5‰ and −3.1 ± 1.3‰, respectively). On the Al-Mg isotope diagram (26Mg* versus 27Al/24Mg), primary Al,Ti-diopside, hibonite, melilite, and spinel in the Allende CAIs studied along the canonical isochron with inferred initial 26Al/27Al ratio [(26Al/27Al)0] of ~5 × 10−5. All secondary minerals have resolved excesses of 26Mg*: alumoåkermanite, corundum, and grossite plot below the canonical isochron, whereas most spinel analyses plot above it. An internal isochron defined by the coexisting secondary corundum and alumoåkermanite in 3529Z has (26Al/27Al)0 = (7.5 ± 2.6) × 10−7. We conclude that the corundum-bearing assemblages in Allende CAIs resulted from metasomatic alteration of primary melilite and anorthite, ~4–5 Ma after their crystallization. Metasomatic alteration of CAIs in the Allende parent asteroid by an aqueous fluid having Δ17O of ~ −3 ± 2‰ modified the O-isotope composition of their primary melilite, anorthite, and Ti-rich pyroxene; O-isotope compositions of primary hibonite, spinel, and low-Ti pyroxene escaped this modification.

¹Johannes Lier,¹Christian Vollmer,¹Linus Risthaus,^2,3Demie Kepaptsoglou,^2,4Quentin M. Ramasse,²Aleksander B. Mosberg,⁵Ashley J. King,^5,6Charlotte L. Bays,⁵Paul F. Schofield
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70027]
¹Institut für Mineralogie, Universität Münster, Münster, Germany
²SuperSTEM Laboratory, Daresbury, UK
³School of Physics, Engineering and Technology, University of York, Heslington, UK
⁴School of Chemical and Process Engineering and School of Physics and Astronomy, University of Leeds, Leeds, UK
⁵Planetary Materials Group, Natural History Museum, London, UK
⁶Department of Earth Sciences, Royal Holloway, University of London, Egham, UK
Published by arrangement with JohnWiley & Sons

Samples of observed meteorite falls provide important constraints on alteration histories of Solar System materials. Due to its rapid collection, terrestrial alteration in the observed Mighei-type (CM) carbonaceous chondrite fall Winchcombe was minimal. In this work, the petrography and mineralogy of three Winchcombe lamellae, two from the matrix and one from a lithological clast, were analyzed by transmission electron microscopy. Our results demonstrate that the matrix of Winchcombe is dominated by Mg-Fe-rich serpentine-type phyllosilicates and tochilinite-cronstedtite intergrowth (TCI)-like phases with variable, but generally high (petrologic type 2.0–2.3) alteration degrees that agree with petrologic types acquired on TCIs on larger scales in other work. However, we also located pristine areas in investigated lamellae such as homogeneous amorphous silicates and glassy particles with sulfide and metal inclusions that resemble altered cometary GEMS (glass with embedded metal and sulfides). One distinct GEMS-like domain shows Fe-rich metal and sulfide grains with oxygen-enriched rims in a Mg-rich amorphous groundmass embedded in organic matter, which likely shielded it from more severe alteration. Fe-Ni-sulfides are mainly pentlandite and concentrated in matrix lamellae. In addition to the sub-μm scale brecciated texture, the three lamellae show different alteration extents, further demonstrating the complex alteration nature of this CM2 meteorite.