¹Ebihara, M. et al. (>10)*
¹Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
*Find the extensive, full author and affiliation list on the publishers website

Two silicate grains (RB-QD04-0049 and RA-QD02-0064, whose estimated masses are 0.050 μg and 0.048 μg, respectively) recovered from the asteroid Itokawa by the Hayabusa spacecraft were studied for their mineralogical characteristics by synchrotron X-ray diffraction and synchrotron X-ray microtomography and further analyzed for their bulk chemical compositions by instrumental neutron activation analysis (INAA). According to X-ray tomography, RB-QD004-0049 is composed of olivine, high-Ca pyroxene, plagioclase, Ca-phosphate, and troilite, whereas RA-QD002-0064 entirely consists of olivine. INAA data are consistent with these mineral compositions except for rare earth elements (REEs). Although the grain RB-QD004-0049 contains measurable REEs, which seems to be consistent with the presence of Ca-phosphate, their abundances are anomalously high. Very low abundance of Co implies less than 0.1 mass% of metals in these two grains by calculation, which is in contrast to the result for the previously analyzed grain RA-QD02-0049 (Ebihara et al., 2011). FeO/Sc ratios of the grains fall within the range of those for ordinary chondrite olivines, implying that these grains are extraterrestrial in origin. FeO/MnO ratios also confirm this conclusion and further suggest that the Hayabusa grains analyzed in this study are similar to material found in LL chondrites rather than CK chondrites although olivines from LL and CK chondrites have similar Fa# (molar% of Fe relative to [Fe+Mg] in olivine) (~30) to those of the Hayabusa grains including the two grains analyzed in this study.

Reference
Ebihara M et al. (2015) Chemical and mineralogical compositions of two grains recovered from asteroid Itokawa. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12418]

Publsihed by arrangement with John Wiley&Sons

^1,2Hezel, D. C. et al. (>10)*
¹Department of Mineralogy, Natural History Museum, London, UK
²Department of Geology and Mineralogy, University of Cologne, Köln, Germany
*Find the extensive, full author and affiliation list on the publishers website

Meteorite fusion crust formation is a brief event in a high-temperature (2000–12,000 K) and high-pressure (2–5 MPa) regime. We studied fusion crusts and bulk samples of 10 ordinary chondrite falls and 10 ordinary chondrite finds. The fusion crusts show a typical layering and most contain vesicles. All fusion crusts are enriched in heavy Fe isotopes, with δ56Fe values up to +0.35‰ relative to the solar system mean. On average, the δ56Fe of fusion crusts from finds is +0.23‰, which is 0.08‰ higher than the average from falls (+0.15‰). Higher δ56Fe in fusion crusts of finds correlate with bulk chondrite enrichments in mobile elements such as Ba and Sr. The δ56Fe signature of meteorite fusion crusts was produced by two processes (1) evaporation during atmospheric entry and (2) terrestrial weathering. Fusion crusts have either the same or higher δ18O (0.9–1.5‰) than their host chondrites, and the same is true for Δ17O. The differences in bulk chondrite and fusion crust oxygen isotope composition are explained by exchange of oxygen between the molten surface of the meteorites with the atmosphere and weathering. Meteorite fusion crust formation is qualitatively similar to conditions of chondrule formation. Therefore, fusion crusts may, at least to some extent, serve as a natural analogue to chondrule formation processes. Meteorite fusion crust and chondrules exhibit a similar extent of Fe isotope fractionation, supporting the idea that the Fe isotope signature of chondrules was established in a high-pressure environment that prevented large isotope fractionations. The exchange of O between a chondrule melt and an 16O-poor nebula as the cause for the observed nonmass dependent O isotope compositions in chondrules is supported by the same process, although to a much lower extent, in meteorite fusion crusts.

Reference
Hezel DC et al. (2015) Fe and O isotope composition of meteorite fusion crusts: possible natural analogues to chondrule formation? Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12414]
Published by arrangement with John Wiley&Sons

¹Steven J. Jaret,¹William R. Woerner,¹Brian L. Phillips,^1,2Lars Ehm,¹Hanna Nekvasil,^3,4Shawn P. Wright,¹Timothy D. Glotch
¹Department of Geosciences, Stony Brook University, Stony Brook, NY
²Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY
³Department of Geosciences, Auburn University, Auburn, AL
⁴Planetary Science Institute, Tucson, AZ

We present the results of a combined study of shocked labradorite from the Lonar Crater, India, using optical microscopy, micro-Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, high-energy X-ray total scattering experiments, and micro-Fourier transform infrared (micro-FTIR) spectroscopy. We show that maskelynite of shock class 2 is structurally more similar to fused glass than to crystalline plagioclase. However, there are slight but significant differences – preservation of original pre-impact igneous zoning, anisotropy at infrared wavelengths, X-ray anisotropy, and preservation of some intermediate range order – which are all consistent with a solid-state transformation from plagioclase to maskelynite.

Reference
Jaret SJ, Woerner WR, Phillips BL, Ehm L,Nekvasil H, Wright SP, Glotch TD (2015) Maskelynite Formation via Solid-State Transformation: Evidence of Infrared and X-Ray Anisotropy. Journal of Geophysical Research Planets (in Press)
Link to Article [10.1002/2014JE004764]

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¹Fumio Kitajima et al. (>10)*
¹Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University, Hakozaki 812-8581, Fukuoka, Japan
*Find the extensive, full author and affiliation list on the publishers website

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Kitajima F et al. (2015) A micro-Raman and infrared study of several Hayabusa category 3 (organic) particles. Earth, Planets & Space 67:20

Link to Article [doi:10.1186/s40623-015-0182-6]

¹Abrar H. Quadery,¹Shaun Pacheco,¹Alan Au,¹Natalie Rizzacasa,¹Joshua Nichols,¹Timothy Le,¹Cameron Glasscock,^1,2Patrick K. Schelling
¹Department of Physics, University of Central Florida, Orlando, Florida, USA
²Advanced Material Processing and Analysis Center, University of Central Florida, Orlando, Florida, USA

Classical molecular dynamics was used to study the annealing of anion and cation Frenkel defects in olivine and orthopyroxene minerals. While it was found that for both minerals, reorganization of the Si-O bonds, often accompanied by large Si displacements, occurs to maintain the fourfold coordination of the SiO4 tetrahedra, important differences are observed in their annealing behavior. Specifically, cation defects are substantially more mobile in olivine than in orthopyroxene leading torapid annihilation of cation Frenkel defects and formation of extended defects in olivine. By contrast, the diffusion rate of anion defects in orthopyroxene is much higher than that in olivine, and also exhibits large anisotropy. Consequently, it was found that diffusion in orthopyroxene occurs without significant annihilation of anion Frenkel defects or trapping of anion interstitials or vacancies into clusters. The results obtained here are discussed in the context of space weathering of olivine and orthopyroxene. Specifically, two important observations are made which may explain previous experimental results. First, ion irradiation experiments that show reduced tolerance for radiation damage in orthopyroxene may be explained by the rapid, one-dimensional anion mobility which prevents healing of the lattice. Second, laser heating experiments which show that orthopyroxene has enhanced tolerance to reduction and the evolution of nanophase Fe inclusions could be due to the observed rapid anion diffusion in orthopyroxene, which might allow the bulk to act as a reservoir for the surface.

Reference
Quadery AH,Pacheco S,Au A, Rizzacasa N, Nichols J, Le T, Glasscock C, Schelling PK (2015) Atomic-scale simulation of space weathering in olivine and orthopyroxene. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004683]

Published by arrangement with John Wiley&Sons

¹Allan H. Treiman,²Juliane Gross
¹Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058-1113, U.S.A.
²Department of Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024, U.S.A.

Among the lunar samples that were returned by the Apollo missions are many cumulate plutonic rocks with high Mg# [molar Mg/(Mg+Fe) in %] and abundances of KREEP elements (potassium, rare earth elements, phosphorus, U, Th, etc.) that imply KREEP-rich parental magmas. These rocks, collectively called the magnesian suite, are nearly absent from sampling sites distant from Imbrium basin ejecta, including those of lunar highlands meteorites. This absence has significant implications for the early differentiation of the Moon and its distribution of heat-producing elements (K, Th, U). Here, we analyze a unique fragment of basalt with the mineralogy and mineral chemistry of a magnesian suite rock, in the lunar highlands meteorite Allan Hills (ALH) A81005. In thin section, the fragment is 700 × 300 μm, and has a sub-ophitic texture with olivine phenocrysts, euhedral plagioclase grains (An97-70),and interstitial pyroxenes. Its minerals are chemically equilibrated. Olivine has Fe/Mn ~ 70 (consistent with a lunar origin), and Mg# ~80, which is consistent with rocks of the magnesian suite and far higher than in mare basalts. It has a rich suite of minor minerals: fluorapatite, ilmenite, Zr-armalcolite, chromite, troilite, silica, and Fe metal (Ni = 3.8%, Co = 0.17%). The metal is comparable to that in chondrite meteorites, which suggests that the fragment is from an impact melt. The fragment itself is not a piece of magnesian suite rock (which are plutonic), but its mineralogy and mineral chemistry suggest that its protolith (which was melted by impact) was related to the magnesian suite. However, the fragment’s mineral chemistry and minor minerals are not identical to those of known magnesian suite rocks, suggesting that the suite may be more varied than apparent in the Apollo samples. Although ALHA81005 is from the lunar highlands (and likely from the farside), Clast U need not have formed in the highlands. It could have formed in an impact melt pool on the nearside and been transported by meteoroid impact. Lunar highlands meteorites should be searched for rock fragments related to the magnesian-suite rocks, but the fragments are rare and may have mineral compositions similar to some meteoritic (impactor) materials.

Reference
Treiman AH, Gross J (2015) A rock fragment related to the magnesian suite in lunar meteorite Allan Hills (ALHA) 81005. American Mineralogist, 100, 414-426
Link to Article [doi:10.2138/am-2015-4800]

Copyright: The Mineralogical Society of America

¹Young, E.D., ¹Manning, C.E., ¹Schauble, E.A., ²Shahar, A., ³Macris, C.A., ²Lazar, C., Jordan, M.
¹Department of Earth, Planetary and Space Sciences, UCLA, United States
²Geophysical Laboratory, Carnegie Institution of Washington, United States
³California Institute of Technology, United States

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Young ED, Manning CE, Schauble EA, Shahar A, Macris CA, Lazar C, Jordan M (2015) High-temperature equilibrium isotope fractionation of non-traditional stable isotopes: Experiments, theory, and applications. Chemical Geology 395, 176-195
Link to Article [DOI: 10.1016/j.chemgeo.2014.12.013]

^1,2Prabhjot Kaur, ^1,2Prakash Chauhan, ^1,2A.S. Rajawat, ^1,2A.S. Kiran Kumar
¹Space Applications Centre, ISRO, Ahmedabad-380015, India
²Nirma University, Ahmedabad, India

Study of dark-haloed craters (DHCs) can provide important information about the geology, mineralogy and evolution of certain hidden mare deposits known as cryptomare. Some DHCs have been identified in the Mare Nectaris region of the near side of the Moon. Beaumont L represents one such DHC situated on the western flank of the Nectaris basin. Moon Mineralogical Mapper (M3) images were used to investigate the composition of DHCs. Morphological investigations have been carried out using Terrain mapping Camera (TMC) and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC) images. The morphological details captured by TMC and LROC Narrow Angle Camera (NAC) images provide evidence that Beaumont-L is of impact origin and do not show evidence of a volcanic origin. The compositional analysis using M3 data, indicate the presence of an olivine rich cryptomare unit excavated due to the Beaumont L impact. Our study also confirms that the band I feature in the reflectance spectra of Beaumont L is completely attributable to olivine deposits without contribution from any type of glass/melt deposits. The presence of olivine in Beaumont L suggests either excavation of olivine-rich cryptomare or a subsurface mafic pluton.

Reflectance
Kaur P, Chauhan P, Rajawat AS, Kumar ASK (2015) Study of olivine-rich dark halo crater – Beaumont L in mare Nectaris using High resolution remote sensing data. Icarus (in Press)
Link to Article [doi:10.1016/j.pss.2015.02.001]

Copyright Elsevier

¹R. E. Arvidson et al. (>10)*
¹Dept. of Earth and Planetary Sciences, Washington University in Saint Louis, St. Louis, MO, USA
*Find the extensive, full author and affiliation list on the publishers website

CRISM hyperspectral (1.0-2.65 µm) along-track oversampled observations (ATOs) covering Victoria, Santa Maria, Endeavour, and Ada craters were processed to 6 m/pixel and used in combination with Opportunity observations to detect and map hydrated Mg and Ca-sulfate minerals in the Burns formation. The strongest spectral absorption features were found to be associated with outcrops that are relatively young and fresh (Ada) or preferentially scoured of dust, soil, and coatings by prevailing winds. At Victoria and Santa Maria the scoured areas are on the southeastern rims and walls, opposite to the sides where wind-blown sands extend out of the craters. At Endeavour the deepest absorptions are in Botany Bay, a subdued and buried rim segment that exhibits high thermal inertias, extensive outcrops, and is interpreted to be a region of enhanced wind scour extending up and out of the crater. Ada, Victoria, and Santa Maria outcrops expose the upper portion of the preserved Burns formation and show spectral evidence for the presence of kieserite. In contrast, gypsum is pervasive spectrally in the Botany Bay exposures. Gypsum, a relatively insoluble evaporative mineral, is interpreted to have formed close to the contact with the Noachian crust as rising ground waters brought brines close to and onto the surface, either as a direct precipitate or during later diagenesis. The presence of kieserite at the top of the section is hypothesized to reflect precipitation from evaporatively concentrated brines or dehydration of polyhydrated sulfates, in both scenarios as the aqueous environment evolved to very arid conditions.

Reference
Arvidson RE et al. (2015) Mars Reconnaissance Orbiter and Opportunity Observations of the Burns Formation: Crater-Hopping at Meridiani Planum. Journal of Geopysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004686]

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¹N. Mangold et al. (>10)*
¹Laboratoire de Planétologie et Géodynamique de Nantes, CNRS, UMR6112, Université de Nantes, Nantes, France
*Find the extensive, full author and affiliation list on the publishers website

The Yellowknife Bay formation represents a ~5 m thick stratigraphic section of lithified fluvial and lacustrine sediments analyzed by the Curiosity rover in Gale crater, Mars [Grotzinger et al., 2014]. Previous works have mainly focused on the mudstones that were drilled by the rover at two locations. The present study focuses on the sedimentary rocks stratigraphically above the mudstones by studying their chemical variations in parallel with rock textures. Results show that differences in composition correlate with textures and both manifest subtle but significant variations through the stratigraphic column. Though the chemistry of the sediments does not vary much in the lower part of the stratigraphy, the variations in alkali elements indicate variations in the source material and/or physical sorting. as shown by the identification of alkali feldspars. The sandstones contain similar relative proportions of hydrogen to the mudstones below, suggesting the presence of hydrous minerals that may have contributed to their cementation. Slight variations in magnesium correlate with changes in textures suggesting that diagenesis, through cementation and dissolution modified the initial rock composition and texture simultaneously. The upper part of the stratigraphy (~1m thick) displays rocks with different compositions suggesting a strong change in the depositional system. The presence of float rocks with similar compositions found along the rover traverse suggests some of these outcrops extend further away in the nearby hummocky plains.

Reference
Mangold N. et al. (2015) Chemical variations in Yellowknife Bay formation sedimentary rocks analyzed by ChemCam onboard the Curiosity rover on Mars. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004681]

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