¹Takeshima, Yuko,^1,2Hyodo, Hironobu,³Tsujimori, Tatsuki,⁴Gouzu, Chitaro,
^4,5,6Itaya, Tetsumaru
Minerals 13, 31 Open Access Link to Article [DOI 10.3390/min13010031]
¹Graduate School of Science, Okayama University of Science, Okayama, 700-0005, Japan
²Institute of Frontier Science and Technology, Okayama University of Science, Okayama, 700-0005, Japan
³Center for Northeast Asian Studies, Tohoku University, Aoba, Sendai, 980-8576, Japan
⁴Hiruzen Institute for Geology & Chronology, 2-12 Nakashima, Naka-ku, Okayama, 703-8252, Japan
⁵Japan Geochronology Network, 2-12 Nakashima, Naka-ku, Okayama, 703-8252, Japan
⁶Institute of GeoHistory, Japan Geochronology Network, 1599 Susai, Akaiwa, 701-2503, Japan

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¹Ming Ma,¹Chen Jingran,^2,3Shengbo Chen,²Peng Lu,¹Chao Sun,¹Chenghao Han
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115645]
¹School of Surveying and Exploration Engineering, Jilin Jianzhu University, Changchun 130118, China
²School of Geo-Exploration Science and Techniques, Jilin University, Changchun 130026, China
³Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei 230026, China
Copyright Elsevier

Topographic correction for lunar optical and thermal infrared remote sensing images is a challenging task. Although geometrical, photometrical or albedo-dependent correction methods have been used in an attempt to eliminate topographic effects in the initial lunar reflectance and emissivity images, these methods did not perform well on lunar steep slopes, large crater interiors or walls. In this paper, a novel neural network topographic correction (NNTC) model that was trained based on the relationships between flat (< 0.1° slope angle) and rugged pixels with similar Kaguya FeO abundance and optical maturity parameters (OMATs) (relative ratio < 0.1%) was applied to the Lunar Reconnaissance Orbiter (LRO) Diviner standard Christiansen feature (CF) image. The topographic correction accuracy is 0.03 μm, and no outliers are produced. Visual comparisons with the previous topographic corrected reflectance and emissivity images indicate that the topographic effects on various slope and aspect pixels were effectively corrected. The excavated anorthosite materials in the highland crater (such as the Jackson, Giordano Bruno and Tycho) interiors, surroundings, ejecta, and ray deposits have very similar NNTC CF values. The crater structures in maria or cryptomaria are identified more clearly. In addition, the NNTC method has the potential to be a universal topographic correction method for lunar optical and thermal infrared images, and it provides reliable data sources and a new method for space weathering correction.

^1,2 Stefanescu, Doru M.
International Journal of Metalcasting (in Press) Link to Article [DOI 10.1007/s40962-023-00971-5]
¹The University of Alabama, Tuscaloosa, AL, United States
²The Ohio State University, Columbus, OH, United States

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¹T. Prabu,¹Kasinathan Muthukkumaran,²I. Venugopal,³S. Anbazhagan
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2023.105710]
¹Dept. of Civil Engineering, National Institute of Technology, Tiruchirappalli, 620015, Tamilnadu, India
²Department of Civil Engineering, M S Ramaiah Institute of Technology, Bangalore, Karnataka, India
³Faculty of Science, Director, Centre for Geoinformatics & Planetary Studies, Professor of Geology, Periyar University, Salem, 636011, Tamilnadu, India

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¹William R. HYDE,²Adam A. GARDE,²Nynke KEULEN,²Sebastian N. MALKKI,^3,4Steven J. JARET,⁵Tod WAIGHT,⁶Pierre BECK,⁷Iain McDONALD,¹Nicolaj K. LARSEN
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.13987]
¹Globe Institute, University of Copenhagen, Copenhagen K, Denmark
²Geological Survey of Denmark and Greenland, Copenhagen K, Denmark
³Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
⁴Department of Physical Sciences, Kingsborough Community College, City University of New York, Brooklyn, New York, USA
⁵Department of Geosciences and Natural Resource Management (Geology Section), University of Copenhagen, Copenhagen K,Denmark
⁶Universit ́e Grenoble Alpes, CNRS, IPAG, Grenoble, France
⁷School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK
Published by arrangement with John Wiley & Sons

Impact melt rocks formed during hypervelocity impact events are ideal forstudying impact structures. Here, we describe impact melt rock samples collected proximalto the 31 km wide 58 Ma Hiawatha impact structure, northwest Greenland, which iscompletely covered by the Greenland Ice Sheet. The melt rocks contain diagnostic shockindicators (e.g., planar deformation features [PDF] in quartz and shocked zircon) and formthree groups based on melt textures and chemistry: (i) hypocrystalline, (ii) glassy, and (iii)carbonate-based melt rocks. The exposed foreland directly in front of the structure consistsof metasedimentary successions and igneous plutons; however, the carbonate-basedimpactites indicate a mixed target sequence with a significant carbonate-rich component.Well-preserved organic material in some melt rocks indicates that North Greenland at thetime of impact was host to abundant organic material, likely a dense high-latitude temperateforest. Geochemical signatures of platinum-group elements in selected samples indicate anextraterrestrial component and support previous identification of a highly fractionated ironimpactor in glaciofluvial sand. Our results illustrate the possibility to study impact structureshidden beneath a thick ice sheet based on transported samples and this opens a new avenuefor identifying other potential impact craters in Greenland and Antarctica.

¹Nicolas D. GARRONI,¹Gordon R. OSINSKI
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.13993]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

Carbonates from the impact melt-bearing breccia in the 2016 IODP/ICDPExpedition 364 drill core at Site M0077 were systematically documented and characterizedpetrographically and geochemically. Calcite, the only carbonate mineral present, is abundantthroughout this deposit as five distinct varieties: (1) subangular carbonate clasts (Type A); (2)subround/irregular carbonate clasts with clay altered rims (Type B); (3) fine-crystalline matrixcalcite (Type C); (4) void-filling sparry calcite (Type D); and (5) microcrystalline carbonatewith flow textures (Type E). Quantitative geochemical analysis shows that calcite in allcarbonate varieties are low in elemental impurities (<2.0 cumulative wt% on average);however, relative concentrations of MgO and MnO vary, which provides distinction betweeneach variety: MgO is highest in calcite from Types A, B, and C carbonates (0.2–0.8 wt% onaverage); MnO is highest in calcite from Types B, C, and D carbonates (0.2–1.3 wt% onaverage); and calcite from Type E carbonate is most pure (<0.1 wt% on average MgO andMnO, cumulatively). Based on textural and geochemical variations between carbonate types,we interpret that some of the carbonate target rocks melted during impact and wereimmiscible within the silicate-dominated melt sheet prior to the resurgence of seawater. TypeB clasts were formed by molten fuel–coolant interaction, as the incoming seawater erodedthrough the melt sheet and encountered carbonate melt (Type E). Post-impact meteoric-dominated hydrothermal activity produced the Mn-elevated calcite from Type C and Dcarbonates, and altered the Type B clasts to be elevated in Mn and host a clay-rich rim.

¹R.C. Greenwood et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13968]
¹Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
Published by arrangement with John Wiley & Sons

As part of an integrated consortium study, we have undertaken O, Cd, Cr, Si, Te, Ti, and Zn whole rock isotopic measurements of the Winchcombe CM2 meteorite. δ66Zn values determined for two Winchcombe aliquots are +0.29 ± 0.05‰ (2SD) and +0.45 ± 0.05‰ (2SD). The difference between these analyses likely reflects sample heterogeneity. Zn isotope compositions for Winchcombe show excellent agreement with published CM2 data. δ114Cd for a single Winchcombe aliquot is +0.29 ± 0.04‰ (2SD), which is close to a previous result for Murchison. δ130Te values for three aliquots gave indistinguishable results, with a mean value of +0.62 ± 0.01‰ (2SD) and are essentially identical to published values for CM2s. ε53Cr and ε54Cr for Winchcombe are 0.319 ± 0.029 (2SE) and 0.775 ± 0.067 (2SE), respectively. Based on its Cr isotopic composition, Winchcombe plots close to other CM2 chondrites. ε50Ti and ε46Ti values for Winchcombe are 3.21 ± 0.09 (2SE) and 0.46 ± 0.08 (2SE), respectively, and are in line with recently published data for CM2s. The δ30Si composition of Winchcombe is −0.50 ± 0.06‰ (2SD, n = 11) and is essentially indistinguishable from measurements obtained on other CM2 chondrites. In conformity with petrographic observations, oxygen isotope analyses of both bulk and micromilled fractions from Winchcombe clearly demonstrate that its parent body experienced extensive aqueous alteration. The style of alteration exhibited by Winchcombe is consistent with relatively closed system processes. Analysis of different fractions within Winchcombe broadly support the view that, while different lithologies within an individual CM2 meteorite can be highly variable, each meteorite is characterized by a predominant alteration type. Mixing of different lithologies within a regolith environment to form cataclastic matrix is supported by oxygen isotope analysis of micromilled fractions from Winchcombe. Previously unpublished bulk oxygen isotope data for 12 CM2 chondrites, when combined with published data, define a well-constrained regression line with a slope of 0.77. Winchcombe analyses define a more limited linear trend at the isotopically heavy, more aqueously altered, end of the slope 0.77 CM2 array. The CM2 slope 0.77 array intersects the oxygen isotope field of CO3 falls, indicating that the unaltered precursor material to the CMs was essentially identical in oxygen isotope composition to the CO3 falls. Our data are consistent with earlier suggestions that the main differences between the CO3s and CM2s reflect differing amounts of water ice that co-accreted into their respective parent bodies, being high in the case of CM2s and low in the case of CO3s. The small difference in Si isotope compositions between the CM and CO meteorites can be explained by different proportions of matrix versus refractory silicates. CMs and COs may also be indistinguishable with respect to Ti and Cr isotopes; however, further analysis is required to test this possibility. The close relationship between CO3 and CM2 chondrites revealed by our data supports the emerging view that the snow line within protoplanetary disks marks an important zone of planetesimal accretion.

¹A.В. VERCHOVSKY,¹F. A. J. ABERNETHY,¹M. ANAND,¹S. J. BARBER,¹R. FINDLAY,¹I. A. FRANCHI,¹R. C. GREENWOOD,¹M. M. GRADY
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.13983]
¹School of Physical Sciences, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

Two bulk Winchcombe along with six other CM2 meteorite samples weresubjected to quantitative evolved gas analysis. The observed release patterns for almost allvolatile species demonstrate close similarity for all the samples and especially between thosefor Winchcombe. This can be considered as a fingerprint for this petrological type ofmeteorites. We identified several gases including H2,H2O, O2, CO, CO2, and SO2releasedin different temperature ranges. The sources and mechanisms of their release were alsoestablished. Some of the gases, H2, CO, and CO2, are released as a result of oxidation ofmacromolecular organic material from oxygen derived from oxygen-bearing minerals (a partof CO2is also released as a result of decomposition of carbonates). The others, O2andH2O, are associated with the phase transformation/decomposition of phyllosilicates and(oxy)hydrates, while a high-temperature release of SO2is associated mostly with thedecomposition of sulfides and in few cases also with sulfates. A low-temperature release ofSO2is due to evaporation and oxidation of elemental sulfur from the meteoritic matrix andorganic material. The total concentrations of H (mostly represented by H2O), C, and S,calculated according to calibration of the quadrupole mass spectrometer with referencegases and decomposition of solid samples (CaSO42H2O and NaHCO3) are in reasonableagreement with those determined by independent methods. Variations in the ratio of thecarbon amounts released as CO2and CO (CCO2/CCO) between the samples could be anindicator of their terrestrial weathering.

¹Gordon R. OSINSKI,¹Adam B. COULTER,¹Roberta L. FLEMMING,¹Alexandra OZARUK,¹Annemarie E. PICKERSGILL,¹Alaura C. SINGLETON
Meteoritics & Planetary Science (in Press) Open Sccess Link to Article [doi: 10.1111/maps.13986]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

The~5 km diameter Gow Lake impact structure formed in the Canadian Shield ofnorthern Saskatchewan approximately 197 Myr ago. This structure has not been studied indetail since its discovery during a regional gravity survey in the early 1970s. We report hereon field observations from a 2011 expedition that, when combined with subsequentlaboratory studies, have revealed a wealth of new information about this poorly studiedCanadian impact structure. Initially considered to be a prototypical central peak (i.e., acomplex) impact structure, our observations demonstrate that Gow Lake is actually atransitional impact structure, making it one of only two identified on Earth. Despite its age,a well-preserved sequence of crater-fill impactites is preserved on Calder Island in themiddle of Gow Lake. From the base upward, this stratigraphy is parautochthonous targetrock, lithic impact breccia, clast-rich impact melt rock, red clast-poor impact melt rock, andgreen clast-poor impact melt rocks. Discontinuous lenses of impact melt-bearing brecciaalso occur near the top of the red impact melt rocks and in the uppermost green impactmelt rocks. The vitric particles in these breccias display irregular and contorted outlines.This, together with their setting within crater-fill melt rocks, is indicative of an origin asflows within the transient cavity and not an airborne mode of origin. Following impact, ahydrothermal system was initiated, which resulted in alteration of the crater-fill impactites.Major alteration phases are nontronite clay, K-feldspar, and quartz.

¹L.C. Chaves,¹M.S. Thompson,²M.J. Loeffler,³C.A. Dukes,⁴P.S. Szabo,¹B.H.N. Horgan 
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115634]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, United States of America
²Department of Physics and Astronomy, Northern Arizona University, 527 South Beaver Street, Flagstaff, AZ 86011, United States of America
³Materials Science and Engineering, University of Virginia, 395 McCormick Road, Charlottesville, VA 22904, United States of America
⁴Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720, United States of America
Copyright Elsevier

Magnetite is a relevant mineral component of asteroids as it has been identified in carbonaceous chondrites, on the surface of asteroid Bennu through remote sensing observations, and in samples returned from asteroid Ryugu. However, the effects of space weathering processes on magnetite have not yet been explored. To investigate how this mineral phase responds to space weathering, here we simulate micrometeoroid bombardment and solar wind irradiation of magnetite using pulsed laser and ion irradiation experiments. We performed X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and visible to near-infrared (VNIR) reflectance spectroscopy analyses to characterize the chemical, microstructural, and spectral response of magnetite to simulated space weathering. In addition, we carried out ion impact simulations using the SDTrimSP software to evaluate the calculated response of magnetite to 1 keV H⁺ and 4 keV He⁺ ions and compared these results to our XPS and TEM results. Ion irradiation simulated ~750 years on the surface of asteroid Bennu, with a solar-wind appropriate total H:He fluence ratio (~24). Within this time, depletion of O was observed with H⁺ and He⁺ ion irradiation, with significantly greater change via protons due to the larger fluence, where preferential sputtering promotes the formation of a metallic iron layer at the magnetite surface. This suggests that solar wind ions act as reducing agents on Fe oxides, with a fraction remaining implanted in these phases. Indeed, we observe elongated defects contained in a crystalline rim created by He⁺ implanted ions in the TEM. Pulsed laser irradiation, analogous to micrometeoroid impacts, generates melts on the surface of the magnetite grains. The impact melts and H⁺-generated metallic iron rims both result in increased VNIR spectral reflectance, but lower fluence He⁺ implantation has no significant spectral effect. These results suggest that space weathered magnetite could contribute to bright regions detected in remote sensing analyses of the Ryugu and Bennu surfaces by the Hayabusa2 and OSIRIS-REx missions and will contribute to the identification and interpretation of space weathered magnetite in returned samples retrieved from both asteroids.