¹Mitsuru Ebihara, ²Naoki Shirai, ³Takahito Osawa, ⁴Akira Yamaguchi
Geochimica Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.10.026]
¹Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
²Department of Chemistry, Kanagawa University, Yokohama, Kanagawa 221-0802, Japan
³Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
⁴National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
Copyright Elsevier

Fifteen elements, including most of the major elements, were quantified using neutron-induced prompt gamma-ray analysis for five Antarctic carbonaceous chondrites with CI affinities and seven with CM affinities. Common among the twelve meteorites is the depletion of volatile elements H and chlorine, showing a positive correlation and being depleted compared to non-Antarctic CI levels. This depletion is not thought to have occurred after the fall on Antarctica, but to have been caused by thermal metamorphism on the parent body. Among the meteorites analyzed in this study, six meteorites (Y-86029, Y 980115, Y-82162 (with CI affinities), Y-86720, Y-86789, B-7904 (with CM affinities)) have previously been proposed to constitute a new meteorite group, the Yamato-type (CY), based on their oxygen isotopic compositions and petrological features. The elemental compositional characteristics of the remaining six meteorites analyzed in this study, Y-86737 and Y 980134 (with CI affinities), and Y-86770, Y-86771, Y-86772 and Y-86773 (with CM affinities), suggest that these meteorites are all classified into the same chemical group CY. Based on the abundance of moderately volatile elements Mn and S, the twelve meteorites can be divided into two groups: one with levels similar to non-Antarctic CI and the other with intermediate levels between CI and CM. These results suggest that CY chondrites originate from two distinct parent bodies. To facilitate further discussions on CY chondrites, we propose naming the groups with compositions close to CI and CM as CYi and CYm, respectively.

¹J. L. MacArthur,¹K. H. Joy,¹R. H. Jones,²T. A. Harvey,³N. V. Almeida
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14273]
¹Department of Earth and Environmental Sciences, University of Manchester, Manchester, UK
²The Geological Society of London, Burlington House, London, UK
³Planetary Materials Group, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The field of advanced curation is important for existing astromaterials collections, which includes samples returned by space missions, and meteorites and cosmic dust samples that have been recovered from here on Earth. In order to maximize the scientific return of the samples, contamination needs to be minimized at all stages of sample collection, preliminary examination, classification, and curation. Utilizing best practice methods, a detailed acquisition and curation plan was implemented during the UK’s first two expeditions to collect Antarctic meteorites from two new blue icefields, Hutchison Icefields and Outer Recovery Icefields. This article documents the design and execution of the procedures used during the project’s curation and classification processes. It describes two case studies showing the processes applied to the recovered meteorites, and reviews our experiences and lessons learned for the future.

^1,2Kohei Fukuda,^3,4Yuki Hibiya,⁵Craig R. Kastelle,⁴Katsuhiko Suzuki,⁶Tsuyoshi Iizuka,⁷Katsuyuki Yamashita,⁵Thomas E. Helser,¹Noriko T. Kita
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14276]
¹WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, USA
²Forefront Research Center, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
³Research Center for Advanced Science and Technology, Graduate School of Science, The University of Tokyo, Meguro, Tokyo, Japan
⁴Submarine Resources Research Center, Japan Agency for Marine-Earth Science Technology, Yokosuka, Kanagawa, Japan
⁵National Oceanic and Atmospheric Administration, Seattle, Washington, USA
⁶Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
⁷Graduate School of Environmental, Life, Natural Science and Technology, Okayama University, Okayama, Okayama, Japan
Published by arrangement with John Wiley & Sons

Understanding the material transport and mixing processes in the Solar protoplanetary disk provides important constraints on the origin of chemical and isotopic diversities of our planets. The limited extent of radial transport and mixing between the inner and outer Solar System has been suggested based on a fundamental isotopic dichotomy between non-carbonaceous (NC) and carbonaceous (CC) meteorite groups. The limited transport and mixing could be further tested by tracing the formation regions of individual meteoritic components, such as Ca-Al-rich inclusions (CAIs) and chondrules. Here, we show further evidence for the outward transport of CAIs and chondrules from the inner and subsequent thermal processing in the outer region of the protoplanetary disk based on the petrography and combined Cr-Ti-O isotope systematics of chondrules from the Vigarano-like (CV) carbonaceous chondrite Allende. One chondrule studied consists of an olivine core that exhibits NC-like Ti and O, but CC-like Cr isotopic signatures, which is enclosed by a pyroxene igneous rim with CC-like O isotope ratios. These observations indicate that the olivine core formed in the inner Solar System. The olivine core then migrated into the outer Solar System and experienced nebular thermal processing that generated the pyroxene igneous rim. The nebular thermal processing would result in Cr isotope exchange between the olivine core and CC-like materials, but secondary alteration effects on the parent body are also responsible for the CC-like Cr isotope signature. By combining previously reported Cr-Ti-O isotope systematics of CV chondrules, we show that some CV chondrules larger than ~1 mm would have formed in the inner Solar System. The accretion of the millimeter-sized, inner Solar System solids onto the CV carbonaceous chondrite parent body would require their very early migration into the outer Solar System within the first 1 million years after the Solar System formation.

¹Robert B. Reid,¹Molly C. McCanta,²Justin Filiberto,³Allan H. Treiman,²Lindsay Keller,⁴Malcolm Rutherford
Journal of Geophysical Resarch (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008485]
¹Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
²NASA Johnson Space Center, Houston, TX, USA
³Lunar and Planetary Institute, Houston, TX, USA
⁴Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
Published by arrangement with John Wiley & Sons

Venus’ surface and interior dynamics remain largely unconstrained, due in great part to the major obstacles to exploration imposed by its 470°C, 90 bar surface conditions and its thick, opaque atmosphere. Flyby and orbiter-based thermal emission data provide opportunities to characterize the surface composition of Venus. However, robust interpretations of such data depend on understanding interactions between the planet’s surface basaltic rocks and its caustic carbon dioxide (CO2)-dominant atmosphere, containing trace amounts of sulfur dioxide (SO2). Several studies, using remote sensing, thermodynamic modeling, and laboratory experiments, have placed constraints on basaltic alteration mineralogy and rates. However, constraints on the effects of SO2-bearing reactions on basalts with diverse compositions remain incomplete. Here, we present new data from a series of gas-solid reaction experiments, in which samples of two basalt compositions were reacted in an SO2-bearing CO2 atmosphere, at relevant Venus temperatures, pressure, and oxygen fugacity. Reacted specimens were analyzed by scanning electron microscopy and scanning transmission electron microscopy using sample cross-sections produced with focused ion beam milling. Surface alteration products were characterized, and their abundances estimated; subsurface cation concentrations were mapped to show the depth of alteration. We demonstrate that the initial development of reaction products progresses rapidly over the course of 30-day runs. Alkaline basalt samples are coated by Na-sulfate (likely thenardite, Na2SO4) and amorphous calcium carbonate (CaCO3) alteration products, and tholeiitic basalt samples are primarily covered by anhydrite (CaSO4), Fe-oxide (FexOy: likely magnetite, Fe3O4), and other minor phases. These mineralogies differ from previous experiments in CO2-only atmospheres.

¹Y. Wu,^1,2Z. Xiao,³Y. Wu,⁴L. Pan,¹P. Yan,^2,6S. Liao,¹Q. Pan,⁷S. Li,^2,6Y. Li,^2,6W. Hsu
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2024JE008412]
¹Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China
²CAS Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
³Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
⁴School of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai, China
⁵Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China
⁶Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
⁷Astronomical Research Center, Shanghai Science & Technology Museum, Shanghai, China
Published by arrangement with John Wiley & Sons

Apatites record crucial information on the origin, composition, and chemical evolution of volatiles on terrestrial planets. As a martian intrusive rock, the gabbroic shergottite Northwest Africa (NWA) 13581 provides key information on the volatile evolution related to magmatic processes in the interior, shedding light on the intricate volatile circulation on Mars. The textural and chemical characteristics of the phosphates in NWA 13581 indicate a complex formation history involving fractional crystallization, degassing, and fluid interaction. Degassing of the NWA 13581 parent melt is capable of exsolving chlorine-rich fluids, resulting in the formation of notably fluorine-rich apatite with a high x-site occupancy of fluorine up to 90%. The degassed/exsolved volatile-rich fluids could subsequently continue to migrate and interact with surrounding magmatic suites, leading to highly heterogeneous compositions of active fluids. The crystallization of apatite is initiated by the interaction of fluids with merrillite at the late stage of the magmatic process, leading to the formation of phosphate intergrowths. Influenced by the composition and chemical evolution of volatiles in fluids and melts, apatite exhibits notable variability in chlorine compositions both within individual grains and among different grains. Moreover, the presence of magnetite associated with phosphate intergrowth highlights the transportation of metallic components in addition to volatiles from deep layers to shallower depths or to the surface of Mars. This process, which is observed in young shergottites, indicates the persistent presence of hydrothermal systems until recent geological periods, contributing to the generation and circulation of volatiles within the martian interior and on the surface.

¹Juulia-Gabrielle Moreau,¹Argo Jõeleht,²Aleksandra N. Stojic,³Christopher Hamann,³Felix E. D. Kaufmann,¹Peeter Somelar,¹Jüri Plado,⁴Satu Hietala,^5,6Tomas Kohout
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14274]
¹Department of Geology, Institute of Ecology and Earth Science, University of Tartu, Tartu, Estonia
²Institut für Planetologie, Westfälische Wilhelms Universität Münster, Münster, Germany
³Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
⁴Geological Survey of Finland, Kuopio, Finland
⁵School of Electrical Engineering, Aalto University, Espoo, Finland
⁶Institute of Geology of the Czech Academy of Sciences, Prague 6, Czech Republic
Published by arrangement with John Wiley & Sons

Iron sulfide and metal melt veins in chondritic materials are associated with advanced stages of dynamic shock. The shock-induced residual temperatures liquefy the sulfide component and enable melt distribution. However, the distribution mechanism is not yet fully understood. Capillary forces are proposed as agents of melt distribution; yet, no laboratory experiments were conducted to assess the role that capillary forces play in the redistribution of iron sulfide in post-shock conditions. To investigate this further, we conducted thermal experiments under reducing conditions (N2(g)) using dunitic fragments, suitable chondritic analog materials that were doped with synthesized troilite (stoichiometric exact FeS). We observed extensive iron sulfide (troilite) migration that partially resembles that of ordinary chondrites, without the additional influence of shock pressure-induced fracturing. The iron sulfide melt infiltrated grain boundaries and pre-existing fractures that darkened the analog material pervasively. We also observed that the iron sulfide melt, which mobilized into grain boundaries, got systematically enriched in Ni from the surrounding host olivine. Consequently, FeNi metal fractionated from the melt in several places. Our results indicate that capillary forces majorly contribute to melt migration in the heated post-shock environment.

^1,2Mingyeong Lee,¹Minsup Jeong,^1,2Young-Jun Choi
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008406]
¹Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea
²University of Science and Technology, Daejeon, Republic of Korea
Published by arrangement with John Wiley & Sons

Lunar regolith consists of unconsolidated grains with high porosity, called the fairy castle structure. It is closely linked to the lunar opposition effect, which is the effect where brightness sharply increases as the phase angle approaches 0°. However, owing to the Earth’s gravity, it is difficult to reproduce the structure to study the physical characteristics of the lunar fairy castle structure in the laboratory. We designed a lunar fairy castle structure model for 3D printing. These models had high porosity and were simplified to tree-like shapes. Various porous conditions of the surface were considered, represented by the number of trees, maximum trunk length, and maximum branch angle. In this study, a laboratory experiment was conducted to measure the reflectance of simulants with a fairy castle structure within a small phase angle range from 1.4° to 5.0°. The result is analyzed for the sample porosity with the tangential slope of the reflectance S(α), which denotes the strength of the opposition effect. In addition, the results of this study were compared with lunar observation data. The porous samples exhibited a relatively large S(α) value. The influence of branch length and attachment angle was very weak in this study. Samples with a porosity between 0.78 and 0.82 represent the similar S(α) values to the lunar observation data, a mean porosity of lunar regolith. In conclusion, our findings suggest a potential correlation between porosity and the opposition effect in printed samples, proposing a new research approach for understanding the lunar opposition effect.

¹Emma R. Stoutenburg,^2,3Razvan Caracas,⁴Natalia V. Solomatova,¹Andrew J. Campbell
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008525]
¹Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
²Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, Paris, France
³The Center for Planetary Habitability (PHAB), University of Oslo, Oslo, Norway
⁴Laboratoire de Géologie de Lyon LGLTPE UMR5276, CNRS, Ecole Normale Supérieure de Lyon, Centre Blaise Pascal, Lyon, France
Published by arrangement with John Wiley & Sons

Iron hydrides are a potentially dominant component of the metallic cores of planets, primarily because of hydrogen’s ubiquity in the universe and affinity for iron. Using ab initio molecular dynamics, we examine iron hydrides with 0.1, 0.33, 0.5, and 0.6 mol fraction hydrogen up to 100 GPa between 3,000 and 5,000 K to describe how hydrogen content affects the melt structure, hydrogen speciation, equation of state (EOS), atomic diffusivity, and melt viscosity. We find that the addition of hydrogen decreases the average Fe–Fe coordination number and lengthens Fe–Fe bonds, while Fe–H coordination number increases. The pair distribution function of hydrogen at low pressure indicates the presence of molecular hydrogen. By tracking chemical speciation, we show that the amount of molecular hydrogen increases and the number of iron in Hx≥1Fey≥0 clusters decreases as the hydrogen concentration increases. We parameterize a pressure, volume, temperature, and composition EOS and show that the molar volume and Grüneisen parameter of the melts decrease while the compressibility and thermal expansivity increase as a function of hydrogen concentration. We find that hydrogen acts as a lubricant in the melts as the iron and hydrogen become more diffusive and the melts become more inviscid as the hydrogen concentration increases. We estimate 2.7 wt% hydrogen in the Martian core and 0.49–1.1 wt% hydrogen in Earth’s outer core based on comparisons to seismic models, with the assumption that the cores are pure liquid iron-hydrogen alloy, and we compare the small exoplanet population with mass-radius curves of iron hydride planets.

^1,2S.J. vanBommel et al. (>10)
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116355]
¹McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO, USA
²Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA
Copyright Elsevier

The “Planetary Instrument for X-ray Lithochemistry” (PIXL) X-ray spectrometer conducts in situ geochemical analyses of martian rocks and regolith interrogated by the Mars 2020 rover, Perseverance. In addition to quantifying primary rock-forming elements, PIXL can quantify trace elements that in turn can provide additional constraints on the geologic history of Mars. Accurate quantifications of trace elements can require additional analytical techniques to mitigate experimental, background, and crystalline effects within PIXL spectra. In this study, we focus on reducing the impact of these effects and investigate the potential presence of rare earth elements (REEs). The study specifically investigates cerium given its typical relative abundance in many geologic materials compared to other REEs and its potential to mimic fluorescence features produced by organics under deep UV excitation. A detailed analysis of PIXL targets analyzed through the first 887 martian days of the Perseverance mission did not produce any conclusive Ce detections. Phosphorus-enriched materials analyzed by PIXL are estimated to contain sub-675 ppm Ce and sulfate-enriched materials sub-450 ppm Ce. The method presented can help constrain limits on the abundance of additional trace elements of interest that also face a similar analytical burden. PIXL’s potential to assess REE abundances, outside of yttrium, is limited for expected concentrations in surface materials. Determining most REE concentrations in materials interrogated by Perseverance will therefore likely require terrestrial analyses.

^1,2A. G. J. Jurewicz,³A. M. Amarsi,⁴D. S. Burnett,^5,6N. Grevesse
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14272]
¹School of Earth and Space Exploration, Arizona State University Busek Center for Meteorite Studies, Tempe, Arizona, USA
²Department of Earth Science, Dartmouth College, Hanover, New Hampshire, USA
³Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
⁴Department of Geology and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁵Centre Spatial de Liège, Université de Liège, Liège, Belgium
⁶STAR Institute, Université de Liège, Liège, Belgium
Published by arrangement with John Wiley & Sons

CI chondrites have been a proxy for the solar system since the mid-20th century. The photospheric and CI chondrite abundances (P and CI, respectively) show a strong correlation. CI as a proxy is also justified by the (i) smoothness of their abundances plotted as a function of odd mass number and (ii) agreement within the error of P as determined spectroscopically. But our statistical assessment of spectroscopic studies and solar wind from the Genesis mission indicates that the small, ~10%–30%, differences (residuals) between CI and P depend on the 50% condensation temperature (Tc50). So, if CI is to be used as a proxy for P, Cosmochemists may want to add a correction to individual elements. Our work is consistent with two published hypotheses: that (i) residuals are linear with Tc50 and (ii) that elements having Tc50 > 1343 K are depleted relative to those with 495 K < Tc50 < 1343 K in CI. We discuss other interpretations which are also feasible. Understanding these small differences of the CI and P for different elements and their variation with Tc50 can help constrain future models of solar system formation and the history of CI chondrites.