¹Shingo Kameda et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114348]
¹Rikkyo University, Japan
Copyright Elsevier

Global multiband images of the C-type asteroid (162173) Ryugu were obtained by the optical navigation camera telescope (ONC-T) onboard Hayabusa2. The 0.7-μm absorption depth of the surface reflectance spectrum, which indicates the presence of hydrous minerals, was not clearly seen on Ryugu using flat field correction data obtained in the preflight measurement. The flat field correction data were obtained in the preflight calibration test only at room temperatures (24–28 °C), whereas most observations around Ryugu were performed at a charge-coupled device (CCD) temperature of approximately −30 °C. To obtain higher accuracy measurements, we used a new flat field correction method using the Ryugu surface reflection data. We confirmed that the flat-field patterns are different in high and low temperature conditions. The 0.7-μm absorption map generated by the new method shows that the 0.7-μm absorption near the equator (5°N–5°S) is stronger than that from 30°N to 30°S. We found that the excess of the absorption depth at low latitudes was 0.072%, corresponding to 2.7σ. The spectral analysis also shows that the Ryugu surface at low latitudes is bluer than that at high latitudes and bluer materials tend to show stronger 0.7-μm absorption than redder materials, suggesting that this region has been subjected to less space weathering and less solar heating.

¹Noel A.Scudder,¹Briony H.N.Horgan,²Elizabeth B.Rampe,^1,3Rebecca J.Smith,⁴Alicia M.Rutledge
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114344]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USA
²Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Mailcode XI2, 2101 NASA Parkway, Houston, TX 77058, USA
³Department of Geosciences, Stony Brook University, 255 Earth and Space Sciences Building, Stony Brook, NY 11794, USA
⁴Department of Astronomy and Planetary Science, Northern Arizona University, NAU Box 6010, Flagstaff, AZ 86011, USA
Copyright Elsevier

The natural chemical and physical variations that occur within volcanic rocks (petrology) provide critical insights into mantle and crust conditions on terrestrial bodies. Visible/near-infrared (VNIR; 0.3–2.5 μm) and thermal infrared (TIR; 5–50 μm) spectroscopy are the main tools available to remotely characterize these materials from satellites in orbit. However, the accuracy of petrologic information that can be gained from spectra when rocks exhibit complex variations in mineralogy, crystallinity, and microtexture occurring together in natural settings is not well constrained. Here, we compare the spectra of a suite of volcanic planetary analog rocks from the Three Sisters Volcanic Complex, Oregon to their mineralogy, chemistry, and microtexture from X-ray diffraction, X-ray fluorescence, and electron microprobe analysis. Our results indicate that TIR spectroscopy is an effective petrologic tool in such rocks for modeling bulk mineralogy, crystallinity, and mineral chemistry. Given a library with appropriate glass endmembers, TIR modeling can derive glass abundance with similar accuracy as other major mineral groups and provide first-order estimates of glass wt.% SiO2 in glass-rich samples, but cannot effectively detect variations in microtexture and minor oxide minerals. In contrast, VNIR spectra often yield non-unique mineralogic interpretations due to overlapping absorption bands from olivine, glass, and Fe-bearing plagioclase. In addition, we find that sub-micron oxides hosted in transparent matrix material that are common in fine-grained extrusive rocks can lower albedo and suppress mafic absorption bands, leading to very different VNIR spectra in rocks with the same mineralogy and chemistry. Mineralogical interpretations from VNIR spectra should not be treated as rigorous petrologic indicators, but can supplement TIR-based petrology by providing unique constraints on oxide minerals, microtexture, and alteration processes.

¹Steven Goderis,²Mehmet Yesiltas,³Hamed Pourkhorsandi,⁴Naoki Shirai,⁵Manu Poudelet,⁵Martin Leitl,⁶Akira Yamaguchi,³Vinciane Debaille,¹Philippe Claeys
Antarctic Record 65,1-20 Link to Article [doi/10.15094/00016237]
¹Analytical-, Environmental-, and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan
2, B-1050 Brussels, Belgium.
²Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, Turkey 39100. ³Laboratoire G-Time, Université Libre de Bruxelles, CP 160/02, 50, Av. F.D. Roosevelt,
1050 Brussels, Belgium.
⁴Department of Chemistry, Tokyo Metropolitan University, 1-1 Minamiosawa,
19 Hachioji, Tokyo 192-0397.
⁵International Polar Foundation, Rue des vétérinaires, 42c/1 1070, Brussels, 21 Belgium.
⁶National Institute of Polar Research, 10

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^1,2Hamed Pourkhorsandi,¹Vinciane Debaille,^1,3Rosalind M.G.Armytage,^1,4Matthias van Ginneken,²PierreRochette,²JérômeGattacceca
Chemical Geology 652, 120056 Link to Article [https://doi.org/10.1016/j.chemgeo.2020.120056]
¹Laboratoire G-Time, Université Libre de Bruxelles, CP, 160/02, 50, Av. F.D. Roosevelt, 1050 Brussels, Belgium
²Aix-Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
³Jacobs/JETS, NASA Johnson Space Center, 2101 NASA Parkway, Mailcode XI3, Houston, TX, 77058, USA
⁴Royal Belgium Institute of Natural Sciences, rue Vautier 29, B-1000 Bruxelles, Belgium

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¹Masaaki Miyahara,^2,3Akira Yamaguchi,¹Masato Saitoh,¹Kanta Fukimoto,⁴Takeshi Sakai,⁴Hiroaki Ohfuji,⁵Naotaka Tomioka,⁶Yu Kodama,⁷Eiji Ohtani
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13608]
¹Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi‐Hiroshima, 739‐8526 Japan
²National Institute of Polar Research, Tokyo, 190‐8518 Japan
³Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo, 190‐8518 Japan
⁴Geodynamics Research Center, Ehime University, Matsuyama, 790‐8577 Japan
⁵Kochi Institute for Core Sample Research, Japan Agency for Marine‐Earth Science and Technology (JAMSTEC), Nankoku, Kochi, 783‐8502 Japan
⁶Marine Works Japan, Nankoku, Kochi, 783‐8502 Japan
⁷Department of Earth Sciences, Graduate School of Science, Tohoku University, Sendai, 980‐8578 Japan
Published by arrangement with John Wiley & Sons

Shock‐induced melting textures and high‐pressure polymorphs in 178 ordinary chondrites of all chemical groups and petrologic types were investigated. The shock‐induced melting modes were classified into three types, namely pocket, line, and network. The type of shock‐induced melting depends on the petrologic type. The width of the shock‐induced melt increased with increasing the petrologic type number. The approximate estimated shock‐pressure ranges recorded in and around the shock‐induced melts of the H‐group ordinary chondrites based on the identified high‐pressure polymorphs were as follows: H3, less than 2 GPa; H4–H6, 2–6 GPa. For ordinary chondrites of the L/LL group, the values were as follows: L/LL3, 2–6 GPa; L/LL4, 2–14 GPa; L5: 14–20 GPa; LL5, 2–14 GPa; L6, 17–23 GPa; and LL6, 14–18 GPa. After adopting the estimated shock pressures into the onion shell‐structured parent body model, the shock pressure on the surface was much lower than in the interior. One possibility is that the apparent lower shock pressure on the surface is due to spallation during the impact. Considering the features of the high‐pressure polymorphs, the major disruption history of the parent bodies is different in each chemical group, although the L/LL chondrite parent bodies may have a similar major disruption history.

¹Akira Yamaguchi,¹Kazuyuki Shiraishi,²Ralph Harvey
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13624]
¹National Institute of Polar Research, Tachikawa, Tokyo, 190‐8518 Japan
²Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, Ohio, 44106‐7216 USA
Published by arrangement with John Wiley & Sons

^1,2Lukasz Farbaniec,^1,2David J.Chapman,¹Jack R.W.Patten,²Liam C.Smith,³James D.Hogan,⁴Alexander Rack,^1,2Daniel E.Eakins
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114346]
¹Institute of Shock Physics, Imperial College London, London SW7 2AZ, UK
²Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
³Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G2R3, Canada
⁴European Synchrotron Radiation Facility, CS40220, 38043 Grenoble Cedex 9, France
Copyright Elsevier

The relationship between the dynamic mechanical properties of stony meteorites and their microstructures was investigated in-situ for an L-type ordinary chondrite using a split-Hopkinson pressure bar apparatus and ultra-high speed phase-contrast X-ray radiography at the European Synchrotron Radiation Facility (ESRF). Synchrotron X-ray microtomography (CT) was performed both prior to and immediately following dynamic compression to correlate key structural features between the initial microstructure and recovered fragments as well as to identify the leading mechanisms for fracture and fragmentation. Real-time visualization of damage evolution in the specimens revealed the very first cracks to be initiated at the sites of FeNi-metal nodules. These cracks propagated rapidly through the largest group of chondrules (the porphyritic olivine type chondrules) along the loading direction, which led to the formation of column-like fragments. CT analysis of the collected fragments confirmed the dominant mode of fracture to be transgranular with a clear link between FeNi-metal nodule statistics and the size distribution of fragments, emphasizing their role in mechanical failure and fragmentation process. The resulting fragmentation was used to validate the predictions of brittle fragmentation models, and found to be in good agreement with the laboratory-scale impacts. In turn, these models can help unravel the consequences of impact-induced fragmentation processes that have helped shape the solar system.

¹Foucher et al. (>10)
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2021.105162]
¹CNRS, Centre de Biophysique Moléculaire, CNRS, Centre de Biophysique Moléculaire, UPR 4301, Rue Charles Sadron, CS80054, 45071, Orléans Cedex 2, France

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¹Dijun Guo,^1,2,3Wenzhe Fa,⁴Xiaojia Zeng,¹Jun Du,^4,3Jianzhong Liu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114327]
¹Institute of Remote Sensing and Geographical Information System, School of Earth and Space Sciences, Peking University, Beijing, China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
³CAS Center for Excellence in Comparative Planetology, Hefei, China
⁴Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Copyright Elsevier

China’s Chang’e-4 mission has carried out the first ever lunar farside landing exploration on the floor of the Von Kármán crater, a geologically complex region located in the most ancient and deepest South Pole-Aitken (SPA) basin. In order to demonstrate the characteristics of materials in the landing area, we investigated the regional geochemistry and thickness of non-mare ejecta overlaying the mare basalts. Comparative analyses of FeO, TiO2 and Th concentrations suggest that the landing site surface is dominated by non-mare ejecta from nearby craters (e.g., Finsen crater) with part of basaltic materials. The ejecta thickness is estimated based on the excavation depth of dark-haloed and non-dark-haloed craters by using support-vector machine, a supervised machine learning method for classification. The results show that the ejecta thickness in the region of 40 km across the landing site varies from near zero to ~80 m with a mean value of ~41 m. The ejecta at the CE-4 landing site is ~40 m thick, which is comparable to the in situ observations by the Lunar Penetrating Radar onboard the Yutu-2 rover. Our results provide valuable information for interpretation of the on-going returned data and geologic analysis of the Chang’e-4 exploration region.

¹M.R.M.Izawa,^2,3P.L.King,⁴P.Vernazza,^3,5J.A.Berger,³W.A.McCutcheon
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114328]
¹Institute for Planetary Materials, Okayama University – Misasa, 827 Yamada, Misasa, Tottori 682-0122, Japan
²Research School of Earth Sciences, Australian National University Canberra, ACT 2601, Australia
³Inst. Meteoritics, Univ. New Mexico, Albuquerque, NM 87131, USA
⁴Lab. d’Astrophys. de Marseille, Pôle de l’Etoile Site de Château-Gombert 38, Marseille cedex 13, France
⁵NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058, United States
Copyright Elsevier

Salt-rich deposits may be more widespread on planetary surfaces than is generally appreciated. Remote observations, laboratory studies of meteorites, and cosmochemical constraints all point towards widespread occurrences of salts (including halides, sulfates, and (bi)carbonates) on asteroids, icy bodies, Mars, and elsewhere. We have investigated the mid-infrared (1.8–25 μm) reflectance spectral properties of mixtures of chondritic (ordinary, enstatite and carbonaceous) meteorites with potassium bromide; a mid-infrared transmissive salt like all halides. Our results demonstrate that halide-chondrite mixtures provide spectral signatures that either reveal the presence of transmissive materials or provide evidence for highly porous regolith. Previously, the nature of the surfaces of the asteroids 624 Hektor and 21 Lutetia was inferred using a limited range of spectra from halide-chondrite mixtures. Here, we provide an extensive dataset of halide-chondrite mixtures to encompass a wider set of possible surface compositions.