^1,2,3Fengke Cao,^2,3Roberta L. Flemming,^2,4Matthew R. M. Izawa,⁵Steven J. Jaret,⁶Jeffrey R. Johnson
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008574]
¹Research Center for Planetary Science, College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu, China
²Department of Earth Sciences, Western University, London, ON, Canada
³Institute for Earth and Space Exploration, Western University, London, ON, Canada
⁴Institute for Planetary Materials, Okayama University, Misasa, Japan
⁵Department of Earth and Planetary Sciences, American Museum of Natural History, New York, NY, USA
⁶Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
Published by arrangement with John Wiley & Sons

Plagioclase feldspar is a ubiquitous mineral found in planetary bodies such as Earth, Moon, Mars, large igneous asteroids such as Vesta, numerous achondrites, and every class of chondritic meteorite. Because all solid planetary bodies are potentially subject to hypervelocity impacts, understanding the shock response of plagioclase enables a better understanding of the geological histories of planetary bodies. This study investigates the response of andesine and bytownite to high-pressure shock waves using micro-XRD and Raman. Fourteen andesine and 11 bytownite samples, which had been previously shocked to peak pressures of 0–56 GPa, were examined. Micro-XRD revealed characteristic signatures of shock damage, including weakened diffraction intensities and heightened background signal, reflecting structural collapse under high pressures. Andesine-bearing rock showed the onset of amorphization at 28.4–29.6 GPa, progressing to complete amorphization at 47.5–50 GPa. Bytownite-bearing rock displayed a similar trend but with higher pressure thresholds: partial amorphization occurred at 25.5–27.0 GPa, and complete amorphization at 38.2–49 GPa. To quantify the degree of shock experienced by plagioclase minerals, we measured the Full Width at Half Maximum (FWHMχ) of Debye rings (from 2D XRD images) for samples across different shock levels. We established linear regression models between ΣFWHMχ and peak shock pressure for both andesine (0–28.4 GPa) and bytownite (0–25.5 GPa) using data from samples that remained crystalline. The model is particularly effective for low shock levels, while Raman is more effective at higher shock pressures. These quantitative relationships provide a valuable tool for assessing the shock history recorded in plagioclase minerals.

¹Audrey C. Martin,²Joshua P. Emery,^2,3Mark Loeffler,¹Kerri L. Donaldson Hanna
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008331]
¹Department of Physics, University of Central Florida, Orlando, FL, USA
²Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ, USA
³Center for Material Interfaces in Research and Applications, Northern Arizona University, Flagstaff, AZ, USA
Published by arrangement with John Wiley & Sons

Mid-infrared (MIR; 5–35 μm) spectroscopy is often used for mineralogical identification on planetary surfaces. Laboratory spectra aiding remote sensing observations are typically performed in reflection geometries, while MIR spectra of planetary surfaces are typically obtained via emission. Here we explore the validity of Kirchhoff’s Law in converting reflectance to emissivity spectra, focusing on the high-porosity regoliths found on airless bodies such as the Moon and asteroids. Specifically, we compared ambient reflectance, ambient emissivity, and simulated asteroid environment (SAE) spectra of fine-particulate olivine and pyroxene with varying regolith porosities, focusing on how spectral features, including the Christiansen feature (CF), reststrahlen bands (RBs), and transparency features (TF), changed under these different conditions. Our results indicate that Kirchhoff’s Law can be effectively employed to interpret 19 MIR reflectance spectra of high-porosity samples, provided environmental spectral effects (i.e., spectral changes due to different pressure and temperature conditions) are considered.

¹E. Dobrică, ²V. Megevand, ¹A.N. Krot, ³A.J. Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.05.020]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, HI, USA
²Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, France
³Department of Earth and Planetary Sciences, University of New Mexico, NM, USA
Copyright Elsevier

Studies of shock metamorphic effects in apatite and merrillite in nine ordinary chondrites (OCs) of petrologic types 3.5–6 and shock metamorphic stages S1–S5 using transmission electron microscopy (TEM) reveal a correlation between the extent of brittle deformation in phosphates and the shock metamorphic stage of six host meteorites. No correlation is observed in thermally annealed and partially melted phosphates in Kyushu (L6), Paragould (L5), and Hamlet (LL3.5 − 3.9). Apatites in several shocked equilibrated (petrologic type 6) OCs show micro- and nano-scale heterogeneities in volatile elements, suggesting they were locally mobilized during shock metamorphism rather than during thermal metamorphism. In Alfianello (L6, S5) and Kyushu (L6, S5), maskelynite associated with apatite shows clear evidence for melting. We suggest that maskelynite formed during melting processes rather than solid-state deformation, which has significant implications for geochronology and reflects the time of impact rather than the crystallization age of phosphates. Our study demonstrates the inadequacy of optical microscopy methods currently applied to determine shock metamorphic stages of chondrites; incorporation of micro and nanostructural observations will improve the accuracy of these determinations. We suggest that integration of detailed observations of shock and thermal metamorphism and fluid alteration is required for a comprehensive understanding of the secondary processes that modified most small Solar System bodies.

^1,2Nandita Kumari,^2,3Laura B. Breitenfeld,⁴Katherine Shirley,⁵Timothy D. Glotch
Jopurnal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008814]
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USA
²Planetary Science Institute, Tucson, AZ, USA
³Department of Astronomy, Mount Holyoke College, South Hadley, MA, USA
⁴Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, Oxfordshire, USA
⁵Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
Published by arrangement with John Wiley & Sons

The ultramafic and silicic rocks on the lunar surface have played an important role in expanding our knowledge regarding its thermal and magmatic evolution. The surface identification and quantification of these rocks on the global scale can significantly improve our understanding of their spatial extents, relationships and formation mechanisms. Christiansen feature positions using Diviner data have aided in global identification and mapping of relatively silica-rich and silica-poor lithologies on the lunar surface. We have used laboratory thermal infrared spectra of silicic and ultramafic rocks to analyze the variation in Christiansen feature in simulated lunar environment. We have characterized the absolute bulk silica content of the rocks and minerals and their Silica, Calcium, Ferrous iron, Magnesium index. We find that they are linearly correlated to the Christiansen feature despite particle size variations. Furthermore, we find that the Christiansen feature shifts toward longer wavelengths with increase in ilmenite content in the ilmenite-basalt mixtures. We have explored the effect of instrument’s spectral band position on the accuracy of the parabolic method that is currently used for the estimation of Christiansen feature position from Diviner data. We find that this method performs poorly for the estimation of the Christiansen feature for ultramafic and silicic rocks and minerals/mineral mixtures. We propose using a machine learning algorithm to estimate the Christiansen feature with higher accuracy for all kinds of silicate compositions on the Moon. This method will lead to increased accuracy in absolute quantification of bulk silicate composition of the lunar surface at varying spatial scales.

¹Kaydra Barbre,¹Andrew Elwood Madden,¹Caitlin Hodges,¹Megan Elwood Madden
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008650]
¹School of Geosciences, University of Oklahoma, Norman, OK, USA
Published by arrangement with John Wiley & Sons

Ferrihydrite has been observed within the Martian regolith; therefore, ferrihydrite transformation pathways are likely critical to iron cycling and mineral transformation on Mars and other extraterrestrial systems. Data from Mars rovers and orbiters indicate that ferrihydrite is associated with significant salt deposits. Previous studies show these salts likely formed as the planet desiccated and may rehydrate to form modern brines today that strongly influence(d) mineral alteration. We hypothesize that the salts observed on Mars’ surface may help preserve ferrihydrite for longer periods than typically observed on Earth. This study investigates the effects of brine chemistry on ferrihydrite alteration through laboratory experiments. Lab-synthesized ferrihydrite was reacted with near-saturated brines and ultra-pure water at 20°C for 30 days in a series of batch reactor experiments. X-ray diffraction and Raman spectroscopy showed that ferrihydrite was preserved without evidence of dissolution/transformation in near-saturated solutions of MgSO4, Na2SO4, and NaClO4, while additional iron-oxyhydroxide phases formed in other brines. We also compared mineral reaction products formed from freeze-dried ferrihydrite and undried ferrihydrite slurry. The freeze-dried ferrihydrite was more likely to be preserved, whereas ferrihydrite in a slurry resulted in the precipitation of goethite and lepidocrocite, indicating that particle aggregation and/or drying history affect ferrihydrite stability and alteration. Overall, ferrihydrite remained largely unaltered in the presence of concentrated sulfate and perchlorate brines. In the context of soils/regolith observed on Mars, our research demonstrates that ferrihydrite is more likely to be preserved when found in areas where these salts are dominant, and desiccated in a cold/arid environment prior to brine exposure.

^1,2Neha Panwar, ¹Neeraj Srivastava, ³Ankita Yadav, ¹Megha Bhatt, ⁴Christian Wöhler, ¹Anil Bhardwaj
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116641]
¹Planetary Remote Sensing Section, Planetary Sciences Division, Physical Research Laboratory, Ahmedabad 380009, India
²Discipline of Earth Sciences, Indian Institute of Technology, Gandhinagar, India
³Banasthali Vidyapith, Rajasthan, India
⁴Image Analysis Group, TU Dortmund University, Dortmund, Germany
Copyright Elsevier

The Crisium Basin (17.0°N, 59.1°E) is a Nectarian multi-ring basin hosting extensive volcanism inside the basin center and along its four rings. The Crisium Basin is an essential proxy for understanding basin-related magmatic activity on the Moon. A detailed stratigraphy and chronology have been established for the Mare Crisium in several earlier studies. However, there has been no comprehensive study regarding the composition and emplacement timescales of the basalts along the rings of the Crisium Basin. The basalts along the rings of the Crisium Basin have been emplaced within Mare Undarum, Mare Spumans, Mare Anguis, Cleomedes Crater, and Lacus Bonitatis. Our recent study identified Marginis West as an episode of volcanism along the outermost ring of the Crisium Basin. This study, for the first time, examines the compositional diversity and ages of the basalts emplaced along the rings of the Crisium Basin to better understand its geological evolution. We report the youngest volcanic unit emplaced inside the Crisium Basin at ~2.0 Ga inside Mare Anguis. Based on the spectral signatures, we report that the contemporaneously formed mare units within the Crisium Basin are compositionally different, displaying a westward increase in Ca, and large pre-existing crustal structures would have deeply influenced the volcanism within the basin in the region.

^1,2,3Steven J. Jaret,⁴William R. Hyde,⁵Leah Shteynman
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14354]
¹Department Physical Sciences, Kingsborough College CUNY, Brooklyn, New York, USA
²Department Earth and Environmental Sciences, CUNY Graduate Center, New York, New York, USA
³Department Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
⁴Department of Geology, Lund University, Lund, Sweden
⁵School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

New mapping and laboratory studies of the impactites at the Gardnos impact structure (Norway) show a variety of impact-deformed rocks. Our mapping and petrographic analyses have subdivided these breccias into three distinct categories: (a) melt-bearing sueivitic breccias, melt-bearing polymict breccias; (b) melt-free, polymict lithic impact breccias; and (c) monomict lithic impact breccias. This illustrates the dynamic nature of crater floor processes where mixing occurs in multiple ways. Feldspar grains exhibit evidence of intense shear, micro-faults, and alternate twin deformation in feldspar. We also observe the development of additional, amphibole-like planar elements (or cleavage) in biotite. Melt-bearing breccias contain carbon concentrations up to an order of magnitude higher than the target rocks. Unusual textures of carbon petrographically associated with shock and post-shock features in feldspars suggest significant postimpact hydrothermal mobilization of carbon within these rocks. Gardnos, therefore, represents an important terrestrial analog for understanding a suite of impact- and postimpact geologic processes.

¹Ryota Fukai, ²Yusuke Takeda, ^3,4Yuki Masuda, ^4,5Daiki Yamamoto, ⁶Yasuhiro Iba, ⁶Shintaro Sasaki, ⁶Shin Ikegami, ⁷Aya Kubota,⁸Reo Sato, ^1,8Tomohiro Usui
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116648]
¹Astromaterial Science Research Group, Japan Aerospace Exploration Agency
²Scattering and Imaging Division, Japan Synchrotron Radiation Research Institute
³Department of Earth and Planetary Sciences, Institute of Science Tokyo
⁴Centre for Star and Planet Formation, Globe Institute, University of Copenhagen
⁵Department of Earth and Planetary Sciences, Kyushu University
⁶Department of Earth and Planetary Sciences, Hokkaido University
⁷Research Institute for Geo-Resources and Environment, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology
⁸Department of Earth and Planetary Science, The University of Tokyo
Copyright Elsevier

The evolution associated with coagulation/fragmentation processes of dust to planetesimals in the protosolar disk is the critical phase of planet formation in the Solar System. The meteoritic components, such as calcium‑aluminum-rich inclusions (CAIs), will provide essential constraints on the coagulation/fragmentation process in the early stage of the disk. We applied the bright-field grinding tomography method to an Allende meteorite (CV3) slab to visualize the coarse-grained CAIs (CG-CAIs) in a colorized 3D model with high spatial resolution. We found four mm-scale CG-CAIs that experienced deformation and/or fragmentation processes within ~1.8 × 103 mm3 Allende slab. An angular-shaped CG-CAI’s surface showed the anisotropy of red-gray and white sides, which suggests that the fragmentation results in the loss of the primitive Wark-Lovering rim. We also found a vesicular-shaped CG-CAI, which indicates that the fracturing and complex formation process of this CG-CAI likely proceeded prior to the accretion of the Wark-Lovering rim. Our observations reveal that the fragmentation of Allende CAIs occurred during the parent body accretion stage and also in the protosolar disk.

¹Elias Wölfer, ¹Christoph Burkhardt, ²Francis Nimmo, ¹Thorsten Kleine
Earth and Planetary Science Letters 663, 119435 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119435]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Department of Earth and Planetary Sciences, University of California Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA
Copyright Elsevier

The bulk silicate Earth (BSE) is depleted in moderately volatile elements, indicating Earth formed from a mixture of volatile-rich and -poor materials. To better constrain the origin and nature of Earth’s volatile-rich building blocks, we determined the mass-dependent isotope compositions of Ge in carbonaceous (CC) and enstatite chondrites. We find that, similar to other moderately volatile elements, the Ge isotope variations among the chondrites reflect mixing between volatile-rich, isotopically heavy matrix and volatile-poor, isotopically light chondrules. The Ge isotope composition of the BSE is within the chondritic range and can be accounted for as a ∼2:1 mixture of CI and enstatite chondrite-derived Ge. This mixing ratio appears to be distinct from the ∼1:2 ratio inferred for Zn, reflecting the different geochemical behavior of Ge (siderophile) and Zn (lithophile), and suggesting the late-stage addition of volatile-rich CC materials to Earth. On dynamical grounds it has been argued that Earth accreted CC material through a few Moon-sized embryos, in which case the Ge isotope results imply that these objects were volatile-rich, presumably because they were either undifferentiated or accreted volatile-rich objects themselves before being accreted by Earth.

¹Lisa Maria Eckart, ¹Henner Busemann, ¹Daniela Krietsch, ¹Cornelia Mertens, ¹Colin Maden, ²¹Conel M. O’D. Alexander, ^3,4Kevin Righter
Geochimica et Cosmocimica Acta )(in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.04.021]
¹Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland
²Carnegie Institution for Science, 5251 Broad Branch Rd NW, Washington, DC 20015, United States
³NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058, United States
⁴Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627, United States
Copyright Elsevier

Carbonaceous chondrites of the Ornans type (COs) include some of the most primitive meteorites known to date, yet most of them show evidence of having experienced mild degrees of thermal alteration in their parent asteroid. Previous studies on aqueously altered CM, CR, and CY chondrites have shown that the noble gases trapped in various components with distinct susceptibility to alteration can be used to assess the extent of parent body processing. In this study, we investigated the noble gas compositions of 51 CO chondrites ranging from petrologic type 3.0 to 3.8, three suspected Mighei-type chondrites (CMs; MIL 090073, DOM 10121, DOM 10299) initially classified as COs, and DOM 10900 with intermediate properties between CMs and COs. The COs show a noble gas mixture typical for carbonaceous chondrites, deriving from primordial carriers such as presolar grains, phase Q, and the carrier of the Ar-rich/V component, which has been observed in anhydrous chondrites, and occasionally air. Additionally, the newly identified W component could be present, which is highly susceptible to water. Combining our results with CO noble gas data from the literature, we show that the 20Netr/132Xecorr ratios correlate best (decrease) with the degree of thermal alteration, likely related to the abundance of presolar diamonds, and may thus serve as tool to subclassify thermally altered chondrites. Based on its 20Netr/132Xecorr ratio, DOM 10847 (paired with DOM 08006) is the most primitive CO, followed by NWA 13464 and Y-74135. The 20Netr/132Xecorr subclassification tool, however, may not be applicable for intergroup comparisons as the stability of the responsible carriers are sensitive to the chemical environment of the parent body. The abundances of heavy noble gases in bulk CO samples are much higher compared to CO etch residues (remaining after demineralization of a bulk meteorite) from the literature, indicating that other carrier(s) than insoluble organic matter must contribute significantly to the heavy noble gas inventory, which is/are susceptible to thermal alteration. DaG 331 was subclassified in this work to be a CO3.1 using the method by Grossmann and Brearley (2005) and the trend line defined by Davidson et al. (2019).
The COs show a wide range in cosmic ray exposure (CRE) ages between 0.17 ± 0.05 Ma (Isna) and 78 Ma (maximum age determined for Dominion Range [DOM] 18286 with an uncertainty of < 10 %), although the majority of CRE ages are > 10 Ma. DOM 18286 has the highest CRE age reported to date for a carbonaceous chondrite. We did not find any age clusters hinting at a major impact event, nor a correlation between CRE ages and the petrologic types. Strikingly, none of the 63 COs analyzed for their noble gases (including literature) contains solar wind, indicating that this group stems from below the regolith surface layer. The COs and CMs show similar matrix-corrected primordial noble gas abundances, suggesting that they accreted their volatiles from a common reservoir.