Maurizio Gemelli, Massimo D’Orazio and Luigi Folco

Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy

We evaluate the performance of a hand-held XRF (HHXRF) spectrometer for the bulk analysis of iron meteorites. Analytical precision and accuracy were tested on metal alloy certified reference materials and iron meteorites of known chemical composition. With minimal sample preparation (i.e., flat or roughly polished surfaces) HHXRF allowed the precise and accurate determination of most elements heavier than Mg, with concentrations > 0.01% m/m in metal alloy CRMs, and of major elements Fe and Ni and minor elements Co, P and S (generally ranging from 0.1 to 1% m/m) in iron meteorites. In addition, multiple HHXRF spot analyses could be used to determine the bulk chemical composition of iron meteorites, which are often characterised by sulfide and phosphide accessory minerals. In particular, it was possible to estimate the P and S bulk contents, which are of critical importance for the petrogenesis and evolution of Fe-Ni-rich liquids and iron meteorites. This study thus validates HHXRF as a valuable tool for use in meteoritics, allowing the rapid, non-destructive (a) identification of the extraterrestrial origin of metallic objects (i.e., archaeological artefacts); (b) preliminary chemical classification of iron meteorites; (c) identification of mislabelled/unlabelled specimens in museums and private collections and (d) bulk analysis of iron meteorites.

Reference
Gemelli M, D’Orazio M and Folco L (in press) Chemical Analysis of Iron Meteorites Using a Hand-Held X-Ray Fluorescence Spectrometer. Geostandards and Geoanalytical Research
[doi:10.1111/j.1751-908X.2014.00291.x]
Published by arrangement with John Wiley & Sons

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Andreas Nathues^a et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

^aMax Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Göttingen

The Dawn mission’s Framing Camera (FC) observed asteroid (4) Vesta in 2011 and 2012 using seven color filters and one clear filter from different orbits. In the present paper we analyze recalibrated HAMO color cubes (spatial resolution ∼60 m/pixel) with a focus on Dark Material (DM). We present a definition of highly concentrated DM based on spectral parameters, subsequently map the DM across the Vestan surface, geologically classify DM, study its spectral properties on global and local scales, and finally, compare the FC in-flight color data with laboratory spectra.
We have discovered an absorption band centered at 0.72 μm in localities of DM that show the lowest albedo values by using FC data as well as spectral information from Dawn’s imaging spectrometer VIR. Such localities are contained within impact-exposed outcrops on inner crater walls and ejecta material. Comparisons between spectral FC in-flight data, and laboratory spectra of meteorites and mineral mixtures in the wavelength range 0.4 to 1.0 μm, revealed that the absorption band can be attributed to the mineral serpentine, which is typically present in CM chondrites. Dark material in its purest form is rare on Vesta’s surface and is distributed globally in a non-uniform manner. Our findings confirm the hypothesis of an exogenic origin of the DM by the infall of carbonaceous chondritic material, likely of CM type. It further confirms the hypothesis that most of the DM was deposited by the Veneneia impact.

Reference
Nathues et al. (in press) Detection of Serpentine in Exogenic Carbonaceous Chondrite Material on Vesta from Dawn FC Data. Icarus
[doi:10.1016/j.icarus.2014.06.003]
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Louise Alexander^1,2, Joshua F. Snape^2,3,4, Ian A. Crawford^1,2, Katherine H. Joy^3,5 and Hilary Downes^1,2

¹Department of Earth and Planetary Science, Birkbeck College, University of London, London, UK
²The Centre for Planetary Sciences at UCL-Birkbeck, London, UK
³Department of Earth Sciences, University College London, London, UK
⁴Department of Physical Sciences, Open University, Milton Keynes, UK
⁵School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK

New data from a petrological and geochemical examination of 12 coarse basaltic fines from the Apollo 12 soil sample 12023,155 provide evidence of additional geochemical diversity at the landing site. In addition to the bulk chemical composition, major, minor, and trace element analyses of mineral phases are employed to ascertain how these samples relate to the Apollo 12 lithological basalt groups, thereby overcoming the problems of representativeness of small samples. All of the samples studied are low-Ti basalts (0.9–5.7 wt% TiO₂), and many fall into the established olivine, pigeonite, and ilmenite classification of Apollo 12 basaltic suites. There are five exceptions: sample 12023,155_1A is mineralogically and compositionally distinct from other Apollo 12 basalt types, with low pigeonite REE concentrations and low Ni (41–55 ppm) and Mn (2400–2556 ppm) concentrations in olivine. Sample 12023,155_11A is also unique, with Fe-rich mineral compositions and low bulk Mg# (=100 × atomic Mg/[Mg+Fe]) of 21.6. Sample 12023,155_7A has different plagioclase chemistry and crystallization trends as well as a wider range of olivine Mg# (34–55) compared with other Apollo 12 basalts, and shows greater similarities to Apollo 14 high-Al basalts. Two other samples (12023,155_4A, and _5A) are similar to the Apollo 12 feldspathic basalt 12038, providing additional evidence that feldspathic basalts represent a lava flow proximal to the Apollo 12 site rather than material introduced by impacts. We suggest that at least one parent magma, and possibly as many as four separate parent magmas, are required in addition to the previously identified olivine, pigeonite, and ilmenite basaltic suites to account for the observed chemical diversity of basalts found in this study.

Reference
Alexander L, Snape JF, Crawford IA, Joy KH and Downes H (in press) Searching for nonlocal lithologies in the Apollo 12 regolith: A geochemical and petrological study of basaltic coarse fines from the Apollo lunar soil sample 12023,155. Meteoritics & Planetary Science
[doi:10.1111/maps.12319]
Published by arrangement with John Wiley & Sons

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Brendt C. Hyde¹, James M. D. Day², Kimberly T. Tait¹, Richard D. Ash³, David W. Holdsworth⁴ and Desmond E. Moser⁵

¹Department of Natural History, Mineralogy, Royal Ontario Museum, Toronto, Ontario, Canada
²Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, California, USA
³Department of Geology, University of Maryland, College Park, Maryland, USA
⁴Robarts Research Institute, Imaging Research Laboratories, London, Ontario, Canada
⁵Department of Earth Sciences, Western University, London, Ontario, Canada

Terrestrial weathering of hot desert achondrite meteorite finds and heterogeneous phase distributions in meteorites can complicate interpretation of petrological and geochemical information regarding parent-body processes. For example, understanding the effects of weathering is important for establishing chalcophile and siderophile element distributions within sulfide and metal phases in meteorites. Heterogeneous mineral phase distribution in relatively coarsely grained meteorites can also lead to uncertainties relating to compositional representativeness. Here, we investigate the weathering and high-density (e.g., sulfide, spinel, Fe-oxide) phase distribution in sections of ultramafic achondrite meteorite Northwest Africa (NWA) 4872. NWA 4872 is an olivine-rich brachinite (Fo_{63.6 ± 0.5}) with subsidiary pyroxene (Fs_9.7 ± 0.1Wo_{46.3 ± 0.2}), Cr-spinel (Cr# = 70.3 ± 1.1), and weathered sulfide and metal. Raman mapping confirms that weathering has redistributed sulfur from primary troilite, resulting in the formation of Fe-oxide (-hydroxide) and marcasite (FeS₂). From Raman mapping, NWA 4872 is composed of olivine (89%), Ca-rich pyroxene (0.4%), and Cr-spinel (1.1%), with approximately 7% oxidized metal and sulfide and 2.3% marcasite-dominated sulfide. Microcomputed tomography (micro-CT) observations reveal high-density regions, demonstrating heterogeneities in mineral distribution. Precision cutting of the largest high-density region revealed a single 2 mm Cr-spinel grain. Despite the weathering in NWA 4872, rare earth element (REE) abundances of pyroxene determined by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) indicate negligible modification of these elements in this mineral phase. The REE abundances of mineral grains in NWA 4872 are consistent with formation of the meteorite as the residuum of the partial melting process that occurred on its parent body. LA-ICP-MS analyses of sulfide and alteration products demonstrate the mobility of Re and/or Os; however, highly siderophile element (HSE) abundance patterns remain faithful recorders of processes acting on the brachinite parent body(ies). Detailed study of weathering and phase distribution offers a powerful tool for assessing the effects of low-temperature alteration and for identifying robust evidence for parent-body processes.

Reference
Hyde BC, Day JMD, Tait KT, Ash RD, Holdsworth DW and Moser DE (in press) Characterization of weathering and heterogeneous mineral phase distribution in brachinite Northwest Africa 4872. Meteoritics & Planetary Science
[doi:10.1111/maps.12320]
Published by arrangement with John Wiley & Sons

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T. Öhman^1,2,3, G. Y. Kramer^1,2 and D. A. Kring^1,2

¹Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
²Center for Lunar Science and Exploration, NASA Lunar Science Institute
³Now at Arctic Planetary Science Institute, Rovaniemi, Finland

We used Moon Mineralogy Mapper (M³), Arecibo and Mini-RF radar, and Diviner radiometer data with Lunar Reconnaissance Orbiter (LRO) Camera and Kaguya Terrain Camera images to characterize the target, ejecta, and impact melt-rich lithologies in and around lunar central peak crater Kepler. M³ data indicate the impact melt rocks of crater floor to be high-Ca pyroxene dominated, distinct from the low-Ca pyroxene-dominated crater wall. The central uplift is high-Ca pyroxene dominated, and has higher albedo. These observations are consistent with thin mare basalts underlain by noritic Imbrium ejecta, underlain by gabbroic crustal material. M³ data reveal an enigmatic, splash-like feature of melt-rich material on the southeastern (uprange) crater wall and flank. M³ data also highlight halos around Kepler. In detail the halos are slightly variable, but in broad terms they define a consistent feature, offset to the inferred downrange direction, and interpreted to reflect the distribution of glass-bearing impact breccia. The radar data sets show most of the proximal ejecta to be radar-bright. However, Diviner rock abundance data do not indicate the presence of blocks on the surface nor can they be seen using LRO Narrow Angle Camera images. Thus, the blocks giving rise to the enhanced radar signal are buried. Beyond the radar-bright zone, a subtle radar-dark halo emerges, coincident with a region of very low rock abundance in Diviner data. This multidisciplinary approach provides a robust analysis of the main characteristics of a lunar complex crater and reveals previously unidentified features related to the distribution of impact melt.

Reference
Öhman T, Kramer GY and Kring DA (in press) Characterization of melt and ejecta deposits of Kepler crater from remote sensing data. Journal of Geophysical Research: Planets
[doi:10.1002/2013JE004501]
Published by arrangement with John Wiley & Sons

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C.D. Neish^a, J. Madden^b, L.M. Carter^c, B.R. Hawke^d, T. Giguere^d,e, V.J. Bray^f, G.R. Osinski^g, J.T.S. Cahill^h

^aDepartment of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL, 32901
^bFranklin and Marshall College, Lancaster, PA, 17603
^cNASA Goddard Space Flight Center, Greenbelt, MD, 20771
^dUniversity of Hawai’i at Manoa, Honolulu, HI, 96822
^eIntergraph Corporation, Box 75330, Kapolei, HI, 96707
^fLunar and Planetary Laboratory, University of Arizona, Tucson, AZ, 85721
^gCentre for Planetary Science and Exploration, Departments of Earth Sciences and Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7
^hThe Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723

In this study, we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims. Many of these craters were only recently discovered due to their unusual radar properties in the near-global Mini-RF data set. We find that most craters with exterior deposits of impact melt are small, ⩽ 20 km, and that the smallest craters have the longest melt flows relative to their size. In addition, exterior deposits of impact melt are more common in the highlands than the mare. This may be the result of differing target properties in the highlands and mare, the difference in titanium content, or the greater variation of topography in the highlands. We find that 80% of complex craters and 60% of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim, implying that pre-existing topography plays a dominant role in melt emplacement. This is likely due to movement during crater modification (complex craters) or breached crater rims (simple craters). We also find that impact melt flows have very high circular polarization ratios compared to other features on the Moon. This suggests that their surfaces are some of the roughest material on the Moon at the centimeter to decimeter scale, even though they appear smooth at the meter scale.

Reference
Neish CD, Madden J, Carter LM, Hawke BR, Giguere T, Bray VJ, Osinski GR and Cahill JTS (in press) Global distribution of lunar impact melt flows. Icarus
[doi:10.1016/j.icarus.2014.05.049]
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Glenn J. MacPherson¹ and Alexander N. Krot²

¹Department of Mineral Sciences, U.S. National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA
²Hawai‘i Institute of Geophysics and Planetology, School of Ocean, Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i, USA

CV (Vigarano type) carbonaceous chondrites, comprising Allende-like (CV_oxA) and Bali-like (CV_oxB) oxidized and reduced (CV_red) subgroups, experienced differing degrees of fluid-assisted thermal and shock metamorphism. The abundance and speciation of secondary minerals produced during asteroidal alteration differ among the subgroups: (1) ferroan olivine and diopside–hedenbergite solid solution pyroxenes are common in all CVs; (2) nepheline and sodalite are abundant in CV_oxA, rare in CV_red, and absent in CV_oxB; (3) phyllosilicates and nearly pure fayalite are common in CV_oxB, rare in CV_red, and virtually absent in CV_oxA; (4) andradite, magnetite, and Fe-Ni-sulfides are common in oxidized CVs, but rare in reduced CVs; the latter contain kirschsteinite instead. Thus, a previously unrecognized correlation exists between meteorite bulk permeabilities and porosities with the speciation of the Ca-, Fe-rich silicates (pyroxenes, andradite, kirschsteinite) among the CVox and CVred meteorites. The extent of secondary mineralization was controlled by the distribution of water ices, permeability, and porosity, which in turn were controlled by impacts on the asteroidal parent body. More intense shock metamorphism in the region where the reduced CVs originated decreased their porosity and permeability while simultaneously expelling intergranular ices and fluids. The mineralogy, petrography, and bulk chemical compositions of both the reduced and oxidized CV chondrites indicate that mobile elements were redistributed between Ca,Al-rich inclusions, dark inclusions, chondrules, and matrices only locally; there is no evidence for large-scale (>several cm) fluid transport. Published ⁵³Mn-⁵³Cr ages of secondary fayalite in CV, CO, and unequilibrated ordinary chondrites, and carbonates in CI, CM, and CR chondrites are consistent with aqueous alteration initiated by heating of water ice-bearing asteroids by decay of ²⁶Al, not shock metamorphism.

Reference
MacPherson GJ and Krot AN (in press) The formation of Ca-, Fe-rich silicates in reduced and oxidized CV chondrites: The roles of impact-modified porosity and permeability, and heterogeneous distribution of water ices. Meteoritics & Planetary Science
[doi:10.1111/maps.12316]
Published by arrangement with John Wiley & Sons

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Masayuki Uesugi¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹JAXA Space Exploration Center, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, Japan

We report the investigation of cutting methods for Hayabusa samples. The purpose of our study is to explore the possibility of applying multiple analyses to a single particle effectively. We investigated the cutting performance of a blade dicing saw, laser, focused ion beam (FIB), and physical breaking by microindenter. Cutting performance was examined by estimating the aspect ratio of the cut slit, i.e., depth over width of the slit. We also investigated the possible contamination and sample damage by cutting. The result of the investigation shows that we can cut the samples from <50 μm to 500 μm using those methods with aspect ratios from 10 to 20, although they would introduce some contamination or damage to the samples. Our investigations also provide an important basis for the analysis of samples obtained by future sample return missions.

Reference
Uesugi et al. (in press) Investigation of cutting methods for small samples of Hayabusa and future sample return missions. Meteoritics & Planetary Science
[doi:10.1111/maps.12322]
Published by arrangement with John Wiley & Sons

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F. Poulet^a, O. Ruesch^b, Y. Langevin^a, H. Hiesinger^b

^aInstitut d’Astrophysique Spatiale, CNRS/Université Paris Sud, 91405 Orsay Cedex
^bInstitut für Planetologie, Westfälische Wilhelms-Universität Münster, Münster

The observations of the surface of 4 Vesta by the Visible and Infrared Mapping Spectrometer (VIR) onboard the Dawn spacecraft reveals that its composition is dominated by pyroxenes with olivine in very localized spots. To derive new constraints on the surface composition of the asteroid, we apply a scattering model to VIR reflectance spectra. The model is first calibrated by performing a non-linear deconvolution of laboratory spectra of mineral mixtures and howardite eucrite diogenite (HED) meteorites. Abundance estimates of minerals are accurate to within 15–25% for the analyzed samples, while the estimated particle sizes are within the intervals of actual sizes. Grain size effects complicate spectral deconvolution and estimation of modal abundances of samples (both HED and mineral mixtures) that contain olivine. The magnesium-rich olivine detection threshold is 10-20% for large grain sizes (100’s μm) and several 10’s% for small grain sizes (<50 μm). Major expected minerals (low-calcium pyroxenes, high-calcium pyroxenes, plagioclase and olivine) can provide satisfactory fits of VIR spectra with excellent residuals ⩽1%. Terrains with the strongest low-calcium pyroxene signatures are well representative of diogenites. The best fits of any unit are obtained by including Fo70 olivine at an abundance level of 10% to 20%, with an uncertainty of ∼10%. Olivine is therefore likely to be ubiquitous over the whole surface of Vesta. Olivine is coarser grained (a few hundred μm) than other minerals such as orthopyroxene and clinopyroxene (grain sizes typically smaller than 100 μm). Both the grain size variance and the modal mineralogy are consistent with the lithologic size and mineral distributions of howardites containing olivine phenocryst-bearing melt. These howardites are the best petrologic analogues of Vesta. Such a surface assemblage could be the result of successive melting and mixing processes due to impacts. The compositional view confirms that Vesta underwent major homogenization processes, resulting in a relatively uniform modal mineralogy and explaining the lack of specific olivine enrichment in the Rheasilvia ejecta.

Reference
Poulet F, Ruesch O, Langevin Y and Hiesinger H (in press) Modal mineralogy of the surface of Vesta: Evidence for ubiquitous olivine and identification of meteorite analogue. Icarus
[doi:10.1016/j.icarus.2014.06.002]
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L. Neslušan¹ and M. Hajduková jr.²

¹Astronomical Institute, Slovak Academy of Sciences, 05960 Tatranská Lomnica, Slovakia
²Astronomical Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 84504 Bratislava, Slova

Aims. In our overall work, we attempt to predict some new meteor showers associated with as many as possible known periodic comets and to find the generic relationship of some already known showers with these comets. In this paper, we focus our attention on the meteor-shower complex of the long-period comet C/1917 F1 (Mellish), which is the known parent body of the December Monocerotids. Some other showers have also been suggested to be associated with this comet. We map its whole complex here.
Methods. For five perihelion passages of the parent comet in the past, we model associated theoretical streams, with each consisting of 10 000 test particles and follow their dynamical evolution until the present. Subsequently, we analyze the orbital characteristics of the parts of found streams that approach the Earth’s orbit.
Results. We confirm the generic relationship between the studied parent comet and December Monocerotids. The comet is probably also the parent body of the April ρ-Cygnids. The evolution of meteoroids to the orbits of April ρ-Cygnids is very long at about 20 millennia. If we follow even a longer evolutionary period, which is up to 50 millennia, then two diffuse showers with the radiant situated symmetrically to both the December Monocerotids and April ρ-Cygnids showers with respect to the apex of the Earth’s motion occur. Our simulation does not confirm any relationship between C/1917 F1 and the November Orionids, although this shower was found in all three databases of observed orbits.

Reference
Neslušan L and Hajduková jr. M (2014)The meteor-shower complex of comet C/1917 F1 (Mellish). Astronomy & Astrophysics 566:A33.
[doi:10.1051/0004-6361/201423382]
Reproduced with permission © ESO

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