New potential pyrrhotite and pentlandite reference materials for sulfur and iron isotope microanalysis

1,2Chen L.,2,3Liu Y.,2,3Li Y.,2,3,4Li Q.-L.,2,3,4Li X.-H.
Journal of Analytical Atomic SpectrometryVolume 36, 1431-1440 Link to Article [DOI 10.1039/d1ja00029b]
1Institute of Earth Sciences, China University of Geosciences Beijing, Beijing, China
2State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
3Innovation Academy of Earth Science, Chinese Academy of Sciences, Beijing, China
4College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China

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Space weathering of the 3-μm phyllosilicate feature induced by pulsed laser irradiation

1B.S.Prince,2,3M.J.Loeffler
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114736]
1Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, AZ 86011, United States of America
2Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ 86011, United States of America
3Center for Materials Interfaces in Research and Applications, Northern Arizona University, Flagstaff, AZ 86011, United States of America
Copyright Elsevier

Here we present results from pulsed laser irradiation of CI and CM simulant samples in an effort to simulate space weathering on airless bodies via micrometeorite impacts. For this study, we focused on determining what type of alteration occurs in the 3-μm absorption region, as this region will be critical to ascertain compositional information of the surface regolith of hydrated asteroids. Generally, using entirely in situ spectral analysis, we find that the laser produces similar effects in both samples. Specifically, irradiation causes the blue spectral slope to decrease until it is relatively flat and that the sample darkens initially with laser irradiation but brightens back to about half of its original level by the end of the irradiation. Furthermore, we also find that laser irradiation causes the band depth on the 3-μm absorption band to increase by as much as 30%, yet the shape of the entire absorption band does not change and the band minima of the 2.72 μm shifts less than 0.001 μm after laser irradiation. The constancy of the latter two parameters, which will be most critical to compositional analysis, suggests that this spectral region could be very useful to determine the asteroid composition on surfaces on hydrated asteroids that have undergone extensive aqueous alteration even if the surface had been subject to a significant amount of space weathering. Whether the same conclusion will be generally applicable to other surfaces containing minerals with a wide range of aqueous alteration is currently unclear but will be tested in future studies.

Cavezzo, the first Italian meteorite recovered by the PRISMA fireball network. Orbit, trajectory, and strewn-field

1D. Gardiol et al. (>10)
Monthly Notices of the Royal Astronomical Society 501, 1215–1227 Link to Article [https://doi.org/10.1093/mnras/staa3646]
1INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, I-10025 Pino Torinese, TO, Italy

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Structural organization of space polymers

1McGeoch J.E.M.,2McGeoch M.W.
Physics of Fluids 33, 067118 Linkto Article [DOI 10.1063/5.0054860]
1Department of Molecular and Cellular Biology, Harvard University, 52 Oxford St., Cambridge, 02138, Massachusetts, United States
2PLEX Corporation, 275 Martine St., Suite 100, Fall River, 02723, Massachusetts, United States

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Calcium isotope cosmochemistry

1,2,3Valdes M.C.,4,5Bermingham K.R.,6Huang S.,7Simon J.I.
Chemical Geology 581, 120396 Link to Article [DOI 10.1016/j.chemgeo.2021.120396]
1Robert A. Pritzker Center for Meteoritics and Polar Studies, Negaunee Integrative Research Center, The Field Museum of Natural History, Chicago, IL, United States
2Department of Geophysical Sciences, The University of Chicago, Chicago, IL, United States
3Department of Earth Sciences, University of Cambridge, Cambridge, UK, United Kingdom
4Department of Earth and Planetary Science, Rutgers University, Piscataway, NJ, United States
5Department of Geology, University of Maryland, College Park, MD, United States
6Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, NV, United States
7Center for Isotope Cosmochemistry and Geochronology, Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, TX, United States

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Terrestrial planet compositions controlled by accretion disk magnetic field

1,2,3McDonough W.F.,2Yoshizaki T.
Progress in Earth and Planetary Science 8, 39 Link to Article [DOI 10.1186/s40645-021-00429-4]
1Department of Geology, University of Maryland, College Park, 8000 Regents Drive, College Park, 20742, MD, United States
2Department of Earth Science, Tohoku University, 6-3, Aoba, Aramaki, Aoba, Sendai, 980-8578, Japan
3Research Center of Neutrino Sciences, Tohoku University, 6-3, Aoba, Aramaki, Aoba, Sendai, 980-8578, Japan

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Complementary nucleosynthetic isotope anomalies of Mo and W in chondrules and matrix in the Allende carbonaceous chondrite: The case for hydrothermal metamorphism and its implications

1Ian S. Sanders,2Edward R. D. Scott
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13742]
1Department of Geology, Trinity College, Dublin 2, Ireland
2Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i, 96822 USA
Published by arrangement with John Wiley & Sons

The remarkable complementary isotopic relationship in the Allende chondrite between chondrules (depleted in s-process molybdenum and tungsten) and matrix (enriched in these nuclides) has been interpreted as evidence that the anomalies were established during chondrule formation, and that chondrules were, therefore, not made by planetesimal collisions. We question this interpretation, and to better understand the complementary relationship, we review nucleosynthetic isotopic variations of Mo and W in bulk carbonaceous chondrites, their components, and acid leachates extracted from them. Mo isotopic data almost always track a mixing line between pure s-process Mo and s-process-depleted Mo (i.e., with excess p-process and r-process Mo in a fixed ratio). Tungsten data track an equivalent mixing line. Guided by our review, we develop a model suggesting how the isotopic variations in Allende’s chondrules and matrix could be attributable to hydrothermal alteration in the parent body. In our model, anomalous Mo and W, both depleted in s-process isotopes, are easily leached from their carriers in the matrix, then transported in solution and precipitated preferentially in water-deficient components, such as chondrules, where the aqueous solvent is consumed. The model operates after accretion so does not inform chondrule-forming mechanisms. It also goes some way to explaining variations of Mo and W isotopes in Ca-Al-rich inclusions in Allende, and variations of s-process Mo in bulk carbonaceous chondrites.

Nucleosynthetic Pt isotope anomalies and the Hf-W chronology of core formation in inner and outer solar system planetesimals

1Fridolin Spitzer,1Christoph Burkhardt,2Francis Nimmo,1Thorsten Kleine
Earth and Planetary Science Letters 576, 117211 Link to Article [https://doi.org/10.1016/j.epsl.2021.117211]
1Institut für Planetologie, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
2Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
Copyright Elsevier

The 182Hf-182W chronology of iron meteorites provides crucial information on the timescales of accretion and differentiation of some of the oldest planetesimals of the Solar System. Determining accurate Hf-W model ages of iron meteorites requires correction for cosmic ray exposure (CRE) induced modifications of W isotope compositions, which can be achieved using in-situ neutron dosimeters such as Pt isotopes. Until now it has been assumed that all Pt isotope variations in meteorites reflect CRE, but here we show that some ungrouped iron meteorites display small nucleosynthetic Pt isotope anomalies. These provide the most appropriate starting composition for the correction of CRE-induced W isotope variations in iron meteorites from all major chemical groups, which leads to a ∼1 Ma upward revision of previously reported Hf-W model ages. The revised ages indicate that core formation in non-carbonaceous (NC) iron meteorite parent bodies occurred at ∼1–2 Ma after CAI formation, whereas most carbonaceous (CC) iron meteorite parent bodies underwent core formation ∼2 Ma later. We show that the younger CC cores have lower Fe/Ni ratios than the earlier-formed NC cores, indicating that core formation under more oxidizing conditions occurred over a more protracted timescale. Thermal modeling of planetesimals heated by 26Al-decay reveals that this protracted core formation timescale is consistent with a higher fraction of water ice in CC compared to NC planetesimals, implying that in spite of distinct core formation timescales, NC and CC iron meteorite parent bodies accreted about contemporaneously within ∼1 Ma after CAI formation, but at different radial locations in the disk.

Network of thermal cracks in meteorites due to temperature variations: new experimental evidence and implications for asteroid surfaces

1,2Guy Libourel,1Clément Ganino,1Marco Delbo,3Mathieu Niezgoda,4Benjamin Remy,5Lionel Aranda,1Patrick Michel
Monthly Notices of the Royal Astronomical Society 500, 1905–1920 Link to Article [https://doi.org/10.1093/mnras/staa3183]
1Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Université Côte d’Azur, UMR 7293, Boulevard de l’Observatoire, CS 34229, F-06304 Nice Cedex 4, France
2School of Ocean, Earth Science and Technology, Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96821, USA
3Commissariat à l’Energie Atomique et aux Energies Alternatives, CEA/DES/ISAS/DM2S/STMF/LMEC, PC 47, F-91191 Gif-sur-Yvette cedex, France
4Université de Lorraine, Laboratoire d’Energétique et de Mécanique Théorique Appliquée, CNRS, UMR 7563, 2 avenue de la Forêt de Haye, TSA 60604, F-54518 Vandoeuvre-les-Nancy Cedex, France
5Département Chimie et Physique des Solides et des Surfaces, Institut Jean Lamour, Université de Lorraine, UMR 7198, F-54000 Nancy, France

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