¹M. Murphy Quinlan,²A.M. Walker,¹C.J. Davies
Earth and Planetary Science Letters 618, 118284 Link to Article [https://doi.org/10.1016/j.epsl.2023.118284]
¹School of Earth and Environment, University of Leeds, Leeds, UK
²Department of Earth Sciences, University of Oxford, Oxford, UK
Copyright Elsevier

Pallasite meteorites contain evidence for vastly different cooling timescales: rapid cooling at high temperatures (K/yrs) and slow cooling at lower temperatures (K/Myrs). Pallasite olivine also shows contrasting textures ranging from well-rounded to angular and fragmental, and some samples record chemical zoning. Previous pallasite formation models have required fortuitous changes to the parent body in order to explain these contrasting timescales and textures, including late addition of a megaregolith layer, impact excavation, or parent body break-up and recombination. We investigate the timescales recorded in Main Group Pallasite meteorites with a coupled multiscale thermal diffusion modelling approach, using a 1D model of the parent body and a 3D model of the metal-olivine intrusion region, to see if these large-scale changes to the parent body are necessary. We test a range of intrusion volumes and aspect ratios, metal-to-olivine ratios, and initial temperatures for both the background mantle and the intruded metal. We find that the contrasting timescales, textural heterogeneity, and preservation of chemical zoning can all occur within one simple ellipsoidal segment of an intrusion complex. These conditions are satisfied in 13% of our randomly generated models (2200 model runs), with small intrusion volumes (with a mean radius ≲100 m) and colder background mantle temperatures (≲1200 K) favourable. Large rounded olivine can be explained by a previous intrusion of metal into a hotter mantle, suggesting possible repeated bombardment of the parent body. We speculate that the formation of pallasitic zones within planetesimals may have been a common occurrence in the early Solar System, as our model shows that favourable pallasite conditions can be accommodated in a wide range of intrusion morphologies, across a wide range of planetesimal mantle temperatures, without the need for large-scale changes to the parent body. We suggest that pallasites represent a late stage of repeated injection of metal into a cooling planetesimal mantle, and that heterogeneity observed in micro-scale rounding or chemical zoning preservation in pallasite olivine can be explained by diverse cooling rates in different regions of a small intrusion.

¹Brouwers, Marc G.,¹Bonsor, Amy,^2,3Malamud, Uri
Monthly Notices of the Royal Astronomical Society 519, 2646-2662 Open Access Link to Article [DOI
10.1093/mnras/stac3316]
¹Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, United Kingdom
²Department of Physics, Technion − Israel Institute of Technology, Technion City, Haifa, 3200003, Israel
³School of the Environment and Earth Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 6997801, Israel

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Zamiatina, Daria A.,¹Zamyatin, Dmitry A.,¹Mikhalevskii, Georgii B.,¹Chebikin, Nikolai S.
Minerals 13, 686 Link to Article [DOI 10.3390/min13050686]
¹The Zavaritsky Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences, Ekaterinburg, 620016, Russian Federation

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¹Ray D.,¹Shukla A.D.,¹Bhardwaj, Anil
Current Science 124, 1138-1139 Link to Article [ISSN00113891]
¹Physical Research Laboratory, Ahmedabad, 380 009, India

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¹Briony Horgan et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2022JE007612]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West 19 Lafayette, IN 47906
Published by arrangement with John Wiley & Sons

The first samples collected by the Perseverance rover on the Mars 2020 mission were from 60 the Maaz formation, a lava plain that covers most of the floor of Jezero crater. Laboratory 61 analysis of these samples back on Earth would provide important constraints on the petrologic 62 history, aqueous processes, and timing of key events in Jezero crater. However, interpreting 63 these samples requires a detailed understanding of the emplacement and modification history of 64 the Maaz formation. Here we synthesize rover and orbital remote sensing data to link outcrop-65 scale interpretations to the broader history of the crater, including Mastcam-Z mosaics and 66 multispectral images, SuperCam chemistry and reflectance point spectra, RIMFAX ground 67 penetrating radar, and orbital hyperspectral reflectance and high-resolution images. We show 68 that the Maaz formation is composed of a series of distinct members corresponding to basaltic to 69 basaltic-andesite lava flows. The members exhibit variable spectral signatures dominated by 70 high-Ca pyroxene, Fe-bearing feldspar, and hematite, which can be tied directly to igneous 71 grains and altered matrix in abrasion patches. Spectral variations correlate with morphological 72 variations, from recessive layers that produce a regolith lag in lower Maaz, to weathered 73 polygonally fractured paleosurfaces and crater-retaining massive blocky hummocks in upper 74 Maaz. The Maaz members were likely separated by one or more extended periods of time, and 75 were subjected to variable erosion, burial, exhumation, weathering, and tectonic modification. 76 The two unique samples from the Maaz formation are representative of this diversity, and 77 together will provide an important geochronological framework for the history of Jezero crater.

^1,2Jean-Alix Barrat,³Addi Bischoff,⁴Brigitte Zanda
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.07.003]
¹Univ Brest, CNRS, UMR 6539 (Laboratoire des Sciences de l’Environnement Marin), Institut Universitaire Européen de la Mer (IUEM), Place Nicolas Copernic, 29280 Plouzané, France
²Institut Universitaire de France, Paris
³Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
⁴Muséum National d’Histoire Naturelle, Laboratoire de Minéralogie et de Cosmochimie du Muséum, CNRS UMR7202, 61 rue Buffon, 75005 Paris, France
Copyright Elsevier

We report on new trace element analyses of enstatite chondrites (ECs) to clarify their behavior during the metamorphism. During the transition from a type 3 to a type 5 or higher, silicates lose a large portion of their trace elements to sulfides. Our procedure allows us to obtain trace element abundances of the silicate fraction of an EC quite easily. The element patterns of these fractions (especially REE patterns) are quite different for EH and EL chondrites, and are furthermore dependent on the metamorphic grade. This procedure can be usefull to classify meteorites, in particular when the sulfides are altered. Applied to anomalous ECs, it allows direct recognition of the EH affinity of QUE 94204, and suggests that Zakłodzie, NWA 4301, and NWA 4799 derive from the same EH-like body of previously unsampled composition.

We have used the concentrations obtained on the silicate fractions of the most metamorphosed chondrites to discuss the chemical characteristics of the primitive mantles of reduced bodies of EH or EL affinity (i.e., after core segregation). Our data indicate that these mantles are very depleted in refractory lithophile elements (RLEs), particularly in rare earth elements (REEs), and notably show significant positive anomalies in Sr, Zr, Hf, and Ti. These estimates imply that the cores contain most of the REEs, U and Th of these bodies. Interestingly, the inferred primitive mantles of these reduced bodies contrast with that of the Earth. If the Earth accreted essentially from ECs, one would expect similar signatures to be preserved, which is not the case. This mismatch can be explained either by a later homogenization of the bulk silicate Earth, or alternatively, that the materials that were accreted were isotopically similar to ECs, but mineralogically different (i.e., oldhamite-free).

¹Francis M. McCubbin,¹, Jonathan A. Lewis,², Jessica J. Barnes,¹, Jeremy W. Boyce,^1,3Juliane Gross, ⁴Molly C. McCanta,^5,6Poorna Srinivasan, ⁷Brendan A. Anzures,¹Nicole G. Lunning,¹, Stephen M. Elardo,¹Lindsay P. Keller,⁹Tabb C. Prissel,^5,6Carl B. Agee
American Mineralogist 108, 1185-1200 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1185.pdf]
¹NASA Johnson Space Center, Mailcode XI, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
²Lunar and Planetary Laboratory, University of Arizona, 1629 E University Boulevard, Tucson, Arizona 85721, U.S.A.
³Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, U.S.A.
⁴Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, U.S.A. 5
⁵Institute of Meteoritics, University of New Mexico, 200 Yale Boulevard SE, Albuquerque, New Mexico 87131, U.S.A.
⁶Department of Earth and Planetary Sciences, University of New Mexico, 200 Yale Boulevard SE, Albuquerque, New Mexico 87131, U.S.A.
⁷Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
⁸Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, U.S.A.
⁹Jacobs, NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Socuety of America

We conducted a petrologic study of apatite within one LL chondrite, six R chondrites, and six CK
chondrites. These data were combined with previously published apatite data from a broader range of chondrite meteorites to determine that chondrites host either chlorapatite or hydroxylapatite with ≤33 mol% F
in the apatite X-site (unless affected by partial melting by impacts, which can cause F-enrichment of
residual apatite). These data indicate that either fluorapatite was not a primary condensate from the solar
nebula or that it did not survive lower temperature nebular processes and/or parent body processes.
Bulk-rock Cl and F data from chondrites were used to determine that the solar system has a Cl/F ratio of
10.5 ± 1.0 (3σ). The Cl/F ratios of apatite from chondrites are broadly reflective of the solar system Cl/F
value, indicating that apatite in chondrites is fluorine poor because the solar system has about an order
of magnitude more Cl than F. The Cl/F ratio of the solar system was combined with known apatite-melt
partitioning relationships for F and Cl to predict the range of apatite compositions that would form from
a melt with a chondritic Cl/F ratio. This range of apatite compositions allowed for the development of a
crude model to use apatite X-site compositions from achondrites (and chondrite melt rocks) to determine
whether they derive from a volatile-depleted and/or differentiated source, albeit with important caveats
that are detailed in the manuscript. This study further highlights the utility of apatite as a mineralogical
tool to understand the origin of volatiles (including H2O) and the diversity of their associated geological
processes throughout the history of our solar system, including at its nascent stage.

¹Christiaan P. A. van Buchem,^1,2Yamila Miguel,¹Mantas Zilinskas,³Wim van Westrenen
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13994]
¹Leiden Observatory, Leiden University, Leiden, The Netherlands
²SRON Netherlands Institute for Space Research, Leiden, The Netherlands
³Faculty of Science, Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
Published by arrangement with John Wiley & Sons

To date, over 500 short-period rocky planets with equilibrium temperatures above1500 K have been discovered. Such planets are expected to support magma oceans,providing a direct interface between the interior and the atmosphere. This provides a uniqueopportunity to gain insight into their interior compositions through atmosphericobservations. A key process in doing such work is the vapor outgassing from the lavasurface. LavAtmos is an open-source code that calculates the equilibrium chemicalcomposition of vapor above a dry melt for a given composition and temperature. Resultsshow that the produced output is in good agreement with the partial pressures obtainedfrom experimental laboratory data as well as with other similar codes from literature.LavAtmos allows for the modeling of vaporization of a wide range of different mantlecompositions of hot rocky exoplanets. In combination with atmospheric chemistry codes,this enables the characterization of interior compositions through atmospheric signatures.

¹Daisuke Nakashima,¹Yuri Fujioka,¹Kanchi Katayama,¹Tomoyo Morita,¹Mizuha Kikuiri,¹Kana Amano,¹Eiichi Kagawa,¹Tomoki Nakamura
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14036]
¹Department of Earth Science, Tohoku University, Sendai, Japan
Published by arrangement with John Wiley & Sons

Preparation procedures of polished sections of the Ryugu samples returned by theHayabusa2 spacecraft were established through tests using CI and CM chondrites as analogmaterials of the Ryugu samples and processing of the Ryugu samples. The proceduresconsisted of four steps: epoxy-coating, embedding in epoxy cylinders, cutting with a wiresaw, and dry polish by hand. There are three key points for successful preparation of thepolished sections: (1) ethanol-mixed epoxy with low viscosity for reinforcing the fragilesamples, (2) handling under dry conditions to avoid breakup of the samples on contact withliquids due to their highly porous nature, and (3) X-ray computed tomography data forexposing maximum surface areas of target mineral phases and clasts. These key points mayalso be important for processing of samples returned from asteroid Bennu and the MartianMoon Phobos, as those samples are likely to be hydrous carbonaceous chondrite-likematerials. The established procedures induce two side effects: zoning of the polished surfaceof the Ryugu samples in scanning electron microscope images reflecting differences incarbon contents due to permeation of low viscosity epoxy resin into the sample surface andfractures in anhydrous minerals possibly due to shear stress during dry polishing.

¹Teng Ee Yap,¹François L.H. Tissot
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115680]
¹The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
Copyright Elsevier

Nucleosynthetic isotope anomalies of planetary materials provide insight into their genetic ties, informing our understanding of early Solar System isotopic architecture and evolution. Isotope anomalies of non‑carbonaceous (NC) and carbonaceous (CC) materials in multi-element space suggests their variability primarily emerged from mixing between several primordial nebular source regions in the nascent protoplanetary disk. In particular, it has been suggested that the elemental and isotopic compositions of CC meteorites reflect admixtures of NC-like, CI-like, and CAI-like components. Despite the plethora of elements for which isotope anomalies have been characterized, no mixing model has quantitatively reproduced CC meteorite compositions for more than two elements.

In this paper, we leverage the recent characterization of Fe isotope anomalies in NC and CC materials, as well as CAIs, to place new constraints on the evolution of the early Solar System and the origin of the CC chondrites. We first respond to the recent proposal, based on Fe isotope analyses of returned samples from Cb-type asteroid Ryugu, that Ryugu and CI chondrites are genetically distinct from NC and CC bodies, originating from a third “CI reservoir” beyond the location of the CC reservoir. Namely, we propose that the appearance of such a trichotomy in meteoritic heritages arises from the current lack of Fe isotope data for CC achondrites. We go on to present a self-consistent mixing model that explains the Ti, Cr, Fe, and Ca concentrations and isotope anomalies of the CM, CV, CO, CK, and CR chondrite groups via admixing of (i) elementally OC-like material, (ii) CI/Ryugu-like material, (iii) isotopically CAI-like dust, and (iv) CAIs sensu stricto. We find that the CAI-like dust constitutes a major and broadly constant fraction (∼36%) of all CC chondrites, and identify the CI-like component with the bulk composition of the Solar System’s parent molecular cloud, denoting it BMC for “Bulk Molecular Cloud.” We interpret our results in the context of a qualitative model for early Solar System isotopic evolution.