¹Hibiya, Y.,¹Iizuka, T.,²Yamashita, K.,³Yoneda, S.,⁴Yamakawa, A.
Geostandards and Geoanalytical Research (in Press) Link to Article [DOI: 10.1111/ggr.12249]
¹Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
²Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
³Department of Science and Engineering, National Museum of Nature and Science, Tsukuba, 305-0005, Japan
⁴National Institute for Environmental Studies (NIES), 16-2 Onogawa, Tsukuba, 305-8506, Japan

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^1,2Einsle, J.F.,³Eggeman, A.S.,²Martineau, B.H.,⁴Saghi, Z.,²Collins, S.M.,¹Blukis, R.,⁵Bagot, P.A.J.,²Midgley, P.A.,¹Harrison, R.J.
Proceedings of the National Academy of Sciences of the United States of America 115, E11436-E11445 Link to Article [DOI: 10.1073/pnas.1809378115]
¹Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom
²Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, United Kingdom
³School of Materials, University of Manchester, Manchester, M13 9PL, United Kingdom
⁴Commissariat à l’Energie Atomique et aux Energies Alternatives, Laboratoire d’électronique des Technologies de l’Information, MINATEC Campus, Grenoble, F-38054, France
⁵Department of Materials, University of Oxford, Oxford, OX1 3PH, United Kingdom

Meteorites contain a record of their thermal and magnetic history, written in the intergrowths of iron-rich and nickel-rich phases that formed during slow cooling. Of intense interest from a magnetic perspective is the “cloudy zone,” a nanoscale intergrowth containing tetrataenite—a naturally occurring hard ferromagnetic mineral that has potential applications as a sustainable alternative to rare-earth permanent magnets. Here we use a combination of high-resolution electron diffraction, electron tomography, atom probe tomography (APT), and micromagnetic simulations to reveal the 3D architecture of the cloudy zone with subnanometer spatial resolution and model the mechanism of remanence acquisition during slow cooling on the meteorite parent body. Isolated islands of tetrataenite are embedded in a matrix of an ordered superstructure. The islands are arranged in clusters of three crystallographic variants, which control how magnetic information is encoded into the nanostructure. The cloudy zone acquires paleomagnetic remanence via a sequence of magnetic domain state transformations (vortex to two domain to single domain), driven by Fe–Ni ordering at 320^◦C. Rather than remanence being recorded at different times at different positions throughout the cloudy zone, each subregion of the cloudy zone records a coherent snapshot of the magnetic field that was present at 320^◦C. Only the coarse and intermediate regions of the cloudy zone are found to be suitable for paleomagnetic applications. The fine regions, on the other hand, have properties similar to those of rare-earth permanent magnets, providing potential routes to synthetic tetrataenite-based magnetic materials.

^1,2Laura E. Jenkins, ^1,2Roberta L. Flemming, ^1,2Phil J. A. McCausland
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13245]
¹Department of Earth Sciences, The University of Western Ontario, London, Ontario, N6A 5B7 Canada
²Centre for Planetary Science and Exploration (CPSX), The University of Western Ontario, London, Ontario, N6A 5B7 Canada
Published by arrangement with John Wiley & Sons

All Martian meteorites have experienced shock metamorphism to some degree. We quantitatively determined shock‐related strain in olivine crystals to measure shock level and peak shock pressure experienced by five Martian meteorites. Two independent methods employing nondestructive in situ micro X‐ray diffraction (μXRD) are applied, i.e., (1) the lattice strain method, in which the lattice strain value (ε) for each olivine grain is derived from a Williamson–Hall plot using its diffraction pattern (peak width variation with diffraction angle) with reference to a best fit calibration curve of ε values obtained from experimentally shocked olivine grains; (2) the strain‐related mosaicity method, allowing shock stage to be estimated by measuring the streaking along the Debye rings of olivine grain diffraction spots to define their strain‐related mosaic spread, which can then be compared with olivine mosaicity in ordinary chondrites of known shock stage. In this study, both the calculated peak shock pressures and the estimated shock stages for Dar al Gani 476 (45.6 ± 0.6 GPa), Sayh al Uhaymir 005/8 (46.1 ± 2.2 GPa), and Nakhla (18.0 ± 0.6 GPa) compare well with literature values. Formal shock assessments for North West Africa 1068/1110 (53.9 ± 2.1 GPa) and North West Africa 6234 (44.6 ± 3.1 GPa) have not been reported within the literature; however, their calculated peak shock pressures fall within the range of peak shock pressures defining their estimated shock stages. The availability of nondestructive and quantitative μXRD methods to determine shock stage and peak shock pressure from olivine crystals provides a key tool for shock metamorphism analysis.

¹E.Vos,^1,2O.Aharonson,²N.Schorghofer
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.01.018]
¹Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
²Planetary Science Institute, Tucson, AZ 85719, USA
Copyright Elsevier

The layered polar caps of Mars have long been thought to be related to variations in orbit and axial tilt. We dynamically link Mars’s past climate variations with the stratigraphy and isotopic composition of its ice by modeling the exchange of H2O and HDO among three reservoirs. The model shows that the interplay among equatorial, mid-latitude, and north-polar layered deposits (NPLD) induces significant isotopic changes in the cap. The diffusive properties of the sublimation lags and dust content in our model result in a cap size consistent with current Mars. The layer thicknesses are mostly controlled by obliquity variations, but the precession period of 50 kyr dominates the variations in the isotopic composition during epochs of relatively low and nearly constant obliquity such as at present. Isotopic sampling of the top 100 m may reveal climate oscillations unseen in the layer thicknesses and would thus probe recent precession-driven climate cycles.

¹Josefine A.M.Nanne,²Francis Nimmo,³Jeffrey N.Cuzzi,¹Thorsten Kleine
Earth and Planetary Science Letters 511, 44-54 Link to Article [https://doi.org/10.1016/j.epsl.2019.01.027]
¹Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
²Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
³Space Science Division, Ames Research Center, Moffett Field, CA 94035, USA
Copyright Elsevier

The isotopic composition of meteorites reveals a fundamental dichotomy between non-carbonaceous (NC) and carbonaceous (CC) meteorites. However, the origin of this dichotomy—whether it results from processes within the solar protoplanetary disk or is an inherited heterogeneity from the solar system’s parental molecular cloud—is not known. To evaluate the origin of the NC–CC dichotomy, we report Ni isotopic data for a comprehensive set of iron meteorites, with a special focus on groups that have not been analyzed before and belong to the CC group. The new Ni isotopic data demonstrate that the NC–CC dichotomy extends to Ni isotopes, and that CC meteorites are characterized by a ubiquitous ⁵⁸Ni excess over NC meteorites. These data combined with prior observations reveal that, in general, the CC reservoir is characterized by an excess in nuclides produced in neutron-rich stellar environments, such as ⁵⁰Ti, ⁵⁴Cr, ⁵⁸Ni, and r-process Mo isotopes. Because the NC–CC dichotomy exists for refractory (Ti, Mo) and non-refractory (Ni, Cr) elements, and is only evident for nuclides produced in specific, neutron-rich stellar environments, it neither reflects thermal processing of presolar carriers in the disk, nor the heterogeneous distribution of isotopically anomalous Ca–Al-rich inclusions (CAI). Instead, the NC–CC dichotomy reflects the distinct isotopic composition of later infalling material from the solar system’s parental molecular cloud, which affected the inner and outer regions of the disk differently. Simple models of the infall process by themselves can support either infall of increasingly NC-like material onto an initially CC-like disk, or infall of increasingly CC-like material in the absence of disk evolution by spreading. However, provided that CAIs formed close to the Sun, followed by rapid outward transport, their isotopic composition likely reflects that of the earliest infalling material, implying that the composition of the inner disk (i.e., the NC reservoir) is dominated by later infalling material, whereas the outer disk (i.e., the CC reservoir) preserved a compositional signature of the earliest disk. The isotopic difference between the inner and outer disk was likely maintained through the rapid formation of Jupiter, which prevented complete homogenization between material from inside (NC reservoir) and outside (CC reservoir) its orbit.

^1,5Noriyuki Kawasaki,²Changkun Park,³Naoya Sakamoto,²Sun Young Park,⁴Hyun Na Kim,⁵Minami Kuroda,^5,3,1Hisayoshi Yurimoto
Earth and Planetary Science Letters 511, 25-35 Link to Article [https://doi.org/10.1016/j.epsl.2019.01.026]
¹Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210, Japan
²Division of Earth-System Sciences, Korea Polar Research Institute, Incheon 21990, Republic of Korea
³Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo 001-0021, Japan
⁴Department of Geoenvironmental Sciences, Kongju National University, Chungcheongnam-do 32588, Republic of Korea
⁵Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
Copyright Elsevier

Al–Mg mineral isochrons of three Ca–Al-rich inclusions (CAIs) that formed primarily by condensation, one fine-grained, spinel-rich inclusion and two fluffy Type A CAIs, from the reduced CV chondrites Efremovka and Vigarano were obtained by in situ Al–Mg isotope measurements using secondary ion mass spectrometry. The slope of the isochron obtained for the fine-grained, spinel-rich inclusion gives an initial ²⁶Al/²⁷Al value, (²⁶Al/²⁷Al)₀, of (5.19 ± 0.17) × 10⁻⁵. This is essentially identical to the Solar System initial ²⁶Al/²⁷Al determined by whole-rock Al–Mg isochron studies for CAIs in CV chondrites. In contrast, the isochron slopes for the two fluffy Type A CAIs from their Al–Mg mineral isochrons, (4.703 ± 0.082) × 10⁻⁵ and (4.393 ± 0.084) × 10⁻⁵, are significantly lower than the Solar System initial value. The range of (²⁶Al/²⁷Al)₀ values of the three CAIs, from (5.19 ± 0.17) to (4.393 ± 0.084) × 10⁻⁵, corresponds to a formation age spread of 0.17 ± 0.04 Myr. This formation age spread is similar to that of igneous CAIs from CV chondrites. The data suggest that condensation and melting of minerals occurred in the hot nebular gas contemporaneously for ∼0.2 Myr at the very beginning of our Solar System, if ²⁶Al was distributed homogeneously in the CAI forming region. Alternatively, the observed variations in (²⁶Al/²⁷Al)₀ among fluffy Type A CAIs would also raise a possibility of heterogeneous distributions of ²⁶Al in the forming region.

¹S.S.Hopkins,^2,3J.Prytulak,¹J.Barling,⁴S.S.Russell,²B.J.Coles,⁵A.N.Hallidaya
Earth and Planetary Science Letters 511, 12-24 Link to Article [https://doi.org/10.1016/j.epsl.2019.01.008]
¹Department of Earth Sciences, University of Oxford, OX1 3AN, United Kingdom
²Department of Earth Sciences and Engineering, Imperial College, London, SW7 2AZ, United Kingdom
³Department of Earth Sciences, Durham University, DH1 3LE, United Kingdom
⁴Natural History Museum, London, SW7 5BD, United Kingdom
⁵The Earth Institute, Columbia University, Hogan Hall, 2910 Broadway, New York, NY 10025, USA
Copyright Elsevier

We present the first high-precision vanadium (V) isotope data for lunar basalts. Terrestrial magmatic rock measurements can display significant V isotopic fractionation (particularly during (Fe, Ti)oxide crystallisation), but the Earth displays heavy V (i.e. higher ⁵¹V/⁵⁰V) isotopic compositions compared to meteorites. This has been attributed to early irradiation of meteorite components or nucleosynthetic heterogeneity. The Moon is isotopically-indistinguishable from the silicate Earth for many refractory elements and is expected to be similar in its V isotopic composition.

Vanadium isotope ratios and trace element concentrations were measured for 19 lunar basalt samples. Isotopic compositions are more variable (∼2.5‰) than has been found thus far for terrestrial igneous rocks and extend to lighter values. Magmatic processes do not appear to control the V isotopic composition, despite the large range in oxide proportions in the suite. Instead, the V isotopic compositions of the lunar samples are lighter with increasing exposure age (te). Modelling nuclear cross-sections for V production and burnout demonstrates that cosmogenic production may affect V isotope ratios via a number of channels but strong correlations between V isotope ratios and te^⁎ [Fe]/[V] implicate Fe as the primary target element of importance. Similar correlations are found in the latest data for chondrites, providing evidence that most V isotope variation in chondrites is due to recent cosmogenic production via Fe spallation. Contrary to previous suggestions, there is no evidence for resolvable differences between the primary V isotopic compositions of the Earth, Moon, chondrites and Mars.

¹Y.Zhao,^1,2J.de Vries,^1,2A.P.van den Berg,³M.H.G.Jacobs,¹W.van Westrenen
Earth and Planetary Science 511, 1-11 Link to Article [https://doi.org/10.1016/j.epsl.2019.01.022]
¹Faculty of Science, Vrije Universiteit Amsterdam, the Netherlands
²Dept. Earth Sciences, Utrecht University, the Netherlands
³Institute of Metallurgy, Clausthal University of Technology, Germany
Copyright Elsevier
The ilmenite-bearing cumulates (IBC) formed from the solidification of the lunar magma ocean are thought to have significantly affected the long-term evolution of the lunar interior and surface. Their high density is considered to trigger Rayleigh–Taylor instabilities which allow them to sink into the solidified cumulates below and drive a large-scale overturn in the lunar mantle. Knowledge of how the IBC participate in the overturn is important for studying the early lunar dynamo, chemistry of surface volcanism, and the existence of present-day partial melt at the lunar core–mantle boundary. Despite early efforts to study this process as Rayleigh–Taylor instabilities, no dynamical models have quantified the degree of IBC sinking systematically. We have performed quantitative 2-D geodynamical simulations to measure the extent to which IBC participate in the overturn after their solidification, and tested the effect of a range of physical and chemical parameters. Our results show that IBC overturn most likely happened when the magma ocean had not yet fully solidified, with the residual melt decoupling the crust and IBC, resulting in 50–70% IBC sinking. Participation of the last dregs of remaining magma ocean melt is unlikely, leaving its high concentrations of radiogenic elements close to the surface. Our simulations further indicate that foundered IBC can stay relatively stable at the core–mantle boundary until the present day, at temperatures consistent with the presence of a partially molten zone in the deep mantle as inferred from geophysical data. 30–50% of the primary IBC remain at shallow depths throughout lunar history, enabling their assimilation by rising magma to form high-Ti basalts.

¹Loroch, D.,¹Klemme, S.,¹Berndt, J.,¹Rohrbach, A.
Data in Brief 21, 2447-2463 Link to Article [DOI: 10.1016/j.dib.2018.10.100]
¹Institute for Mineralogy, University of Münster, Corrensstrasse 24, Münster, 48149, Germany

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^1,2Dieter Stöffler, ¹Christopher Hamann,³Knut Metzler
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13246]
¹Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, , 10115 Berlin, Germany
²Humboldt‐Universität zu Berlin, , 10099 Berlin, Germany
³Institute of Planetology, University of Münster, , 48149 Münster, Germany
Published by arrangement with John Wiley & Sons

With this addendum we provide some correction and additional information regarding the above cited publication. It addresses the following two topics. (1) Clarification for a correct application of the criteria for certain shock stages of chondrites, in particular stage C‐S6. (2) Correction of a printing error in the table that contains the shock classification system of chondrites.