¹Masayuki Uesugi,²Motoo Ito,³Hikaru Yabuta,⁴Hiroshi Naraoka,⁴Fumio Kitajima,⁵Yoshinori Takano,⁶Hajime Mita,⁷Yoko Kebukawa,⁸Aiko Nakato,⁹Yuzuru Karouji
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13236]
¹Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo, 679‐5198 Japan
²Institute for Core Sample Research, Japan Agency for Marine‐Earth Science Technology (JAMSTEC), Nankoku, Kochi, 783‐8502 Japan
³Department of Earth and Planetary Systems Science, Hiroshima University, Hiroshima, 739‐8526 Japan
⁴Department of Earth and Planetary Science, Faculty of Science, Kyushu University, Hakozaki, Fukuoka, 812‐8581 Japan
⁵Department of Biogeochemistry, Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Yokosuka, 237‐0061 Japan
⁶Life, Environment and Materials Science, Fukuoka Institute of Technology, Fukuoka, 811‐0295 Japan
⁷Faculty of Engineering, Yokohama National University, Yokohama, 240‐8501 Japan
⁸Division of Earth and Planetary Sciences, Kyoto University,Sakyo, Kyoto, 606‐8502 Japan
⁹Space Exploration Innovation Hub Center, Japan Aerospace Exploration Agency (JAXA), , Sagamihara, Kanagawa, 252‐5210 Japan
Published by arrangement with John Wiley & Sons

Carbonaceous materials in the sample catcher of the Hayabusa spacecraft were assigned as category 3 particles. We investigated the category 3 particles with a suite of in situ microanalytical methods. Possible contaminants collected from the cleanrooms of the spacecraft assembly and extraterrestrial sample curation center (ESCuC) were also analyzed in the same manner as category 3 particles for comparison. Our data were integrated with those of the preliminary examination team for category 3 particles. Possible origins for the category 3 particles include contamination before and after the operation of the Hayabusa spacecraft.

¹Morgan A. Cox,¹Aaron J. Cavosie,²Ludovic Ferrière,¹Nicholas E. Timms,¹Phil A. Bland,¹Katarina Miljković,^1,3Timmons M. Erickson,³Brian Hess
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13238]
¹Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, , Perth, WA, 6102 Australia
²Natural History Museum, , A‐1010 Vienna, Austria
³Jacobs‐JETS, Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, , Houston, Texas, 77058 USA
⁴NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin–Madison, , Madison, Wisconsin, 53706 USA
Published by arrangement with John Wiley & Sons

Yallalie is a ~12 km diameter circular structure located ~200 km north of Perth, Australia. Previous studies have proposed that the buried structure is a complex impact crater based on geophysical data. Allochthonous breccia exposed near the structure has previously been interpreted as proximal impact ejecta; however, no diagnostic indicators of shock metamorphism have been found. Here we report multiple (27) shocked quartz grains containing planar fractures (PFs) and planar deformation features (PDFs) in the breccia. The PFs occur in up to five sets per grain, while the PDFs occur in up to four sets per grain. Universal stage measurements of all 27 shocked quartz grains confirms that the planar microstructures occur in known crystallographic orientations in quartz corresponding to shock compression from 5 to 20 GPa. Proximity to the buried structure (~4 km) and occurrence of shocked quartz indicates that the breccia represents either primary or reworked ejecta. Ejecta distribution simulated using iSALE hydrocode predicts the same distribution of shock levels at the site as those found in the breccia, which supports a primary ejecta interpretation, although local reworking cannot be excluded. The Yallalie impact event is stratigraphically constrained to have occurred in the interval from 89.8 to 83.6 Ma based on the occurrence of Coniacian clasts in the breccia and undisturbed overlying Santonian to Campanian sedimentary rocks. Yallalie is thus the first confirmed Upper Cretaceous impact structure in Australia.

¹Michael Willig,¹Andreas Stracke
Earth and Planetary Science Letters 509, 55-65 Link to Article [https://doi.org/10.1016/j.epsl.2018.12.004]
¹Westfälische Wilhelms-Universität Münster, Corrensstr. 24, 48149 Münster, Germany
Copyright Elsevier

Combined Ce and Nd isotope ratios provide a time-integrated record of the light rare earth element (LREE) abundances of their source materials. Here, we present new high precision Ce isotope data for chondrites and basalts from ocean islands (OIB) and mid ocean ridges (MORB). The new Ce isotope ratios in chondritic meteorites define a precise new CHUR reference value. In Ce–Nd isotopic space, the MORB and OIB form a well-defined array that intersects with the Ce–Nd chondritic reference value. The simplest first-order explanation is that the bulk silicate Earth (BSE) has chondritic LREE and Ce–Nd isotope ratios. We show, however, that the intercept and slope of the Ce–Nd isotope mantle array depend on several factors. Perhaps most important are whether the BSE is chondritic and how closely the mantle average reflected in the MORB and OIB data corresponds to the Ce–Nd isotope ratio of the BSE. A significant difference between the accessible mantle’s average Ce–Nd isotope ratio and that of BSE could result from the permanent storage of a considerable proportion of Earth’s total LREE budget in the continental crust or potential isolated reservoirs. We show that the formation of isolated reservoirs either has a minor effect on the average Ce–Nd composition of the average mantle, or is geochemically and geodynamically implausible. If, due to formation of the continental crust, a significant shift in the average mantle’s Ce–Nd isotope composition relative to BSE occurs, this shift is parallel to the Ce–Nd mantle array, and does not affect its chondritic intercept. The chondritic intercept of the Ce–Nd isotope mantle array therefore is strong evidence that BSE’s relative LREE and Ce–Nd isotope composition is chondritic. However, an apparent difference between the accessible mantle’s average Ce–Nd isotope ratio and that of BSE could also result if MORB and OIB do not sample the accessible mantle in a representative manner. Although we cannot entirely exclude the latter, it would require a fortuitous combination of factors to cause the observed chondritic intercept of the Ce–Nd isotope mantle array. We therefore conclude that the bulk silicate Earth has chondritic LREE and Ce–Nd isotope ratios.