^1,2M. Cañada-Assandri, ^1,2R. Gil-Hutton, ³A.O. Ribeiro
¹Complejo Astrónmico El Leoncito (CONICET), Av. España 1512 sur, J5402DSP. San Juan, Argentina
²Universidad Nacional de San Juan, Av. Ignacio de la Roza 590 oeste, J5402DCS. San Juan, Argentina
³Observatorio Nacional, Rua General José Cristino 77, Rio de Janeiro, 20921-400, Brazil

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Reference
Cañada-Assandri M, Gil-Hutton R, Ribeiro AO (2014) The Hungaria population: A comparison between sub-Groups. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2014.11.004]

^1,2,3Xiaoxia Duan,¹Marcel Regelous
¹GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Schloßgarten 5, 91054 Erlangen, Germany
²Institute of Geology and Geophysics, Chinese Academy of Sciences, 100029 Beijing, PR China
²University of Chinese Academy of Sciences, 100049 Beijing, PR China

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Reference
Duan X, Regelous M (2014) Rapid determination of 26 elements in iron meteorites using matrix removal and membrane desolvating quadrupole ICP-MS. Journal Analalytical Atomic Spectrometry 29, 2379-2387.
Link to Article [DOI:10.1039/C4JA00244J]

¹Rahat Khan, ¹Yuta Yokozuka, ¹Saki Terai, ¹Naoki Shirai, ¹Mitsuru Ebihara
¹Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Japan

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Reference
Khan R, Yokozuka Y, Terai S, Shirai N, Ebihara M (2014) Accurate determination of Zn in geological and cosmochemical rock samples by isotope dilution inductively coupled plasma mass spectrometry. Journal Analytical Atomic Spectrometry (in Press)
Link to Article [DOI: 10.1039/C4JA00344F]

¹J. Guignard, ²M.J. Toplis
¹European Synchrotron Radiaton Facility (ESRF), 71 Avenue des Martyrs, 38000, Grenoble
²Institut de Recherche en Astrophysique et Planétologie (UMR5277 CNRS/Université Paul Sabatier), Observatoire Midi-Pyrénées, 14, Av. E. Belin, 31400 Toulouse, France

The textural characteristics of opaque iron-rich phases (kamacite-taenite and troilite) have been quantified in the eight H-chondrites (two H4, three H5 and three H6) that have been the subject of previous thermo-chronological studies. These samples are of interest as they have temperature-time paths during cooling that have been shown to be consistent with radiogenic heating by 26Al on a single parent-body, thus offering the possibility to quantitatively link textural characteristics to thermal history. In addition to these eight samples, two other H5 samples (Forest City & Misshof) and two primitive achondrites (Acapulco & Lodran) were studied for comparison. The textural characteristics measured include: i) phase proportions, ii) the length of metal-sulphide contacts, iii) dihedral angle at contacts with silicate grains, iv) grain shape and circularity, v) grain size and size distributions. The absolute and relative proportions of metals and sulphides are found to be approximately constant in all studied H chondrites, consistent with evolution in a chemically closed system. With increasing degree of thermal metamorphism, H-chondrites are found to show evidence for separation of metal and sulphide phases, increasing grain circularity, increasing grain size, and modification of size distributions characterized by the elimination of small grains. Variations of these parameters are found to be almost identical for sulphides and metals suggesting similar growth mechanisms for these two phases. Furthermore, trends between samples place them consistently in the same order: Sainte Marguerite (H4), Forest Vale (H4), Nadiabondi (H5), Richardton (H5), Forest City (H5), Misshof (H5), Allegan (H5), Kernouvé (H6), Guareña (H6) and Estacado (H6). In all cases Acapulco and Lodran extend the trends observed among the H-chondrites. In general, it is found that characteristics requiring material transport over shorter length scales (i.e. within grains) show greater variation for low petrographic type (H4/H5) and reach textural equilibrium earlier in the sequence than characteristics which require transport over larger distances (i.e. between grains). In the latter case (e.g. slopes of crystal size distribution), variations are most marked for H6 samples, trends that are significantly extended by Acapulco and Lodran, highlighting the role of silicate melt on variations in textural properties. Crystal size distributions imply normal grain growth (NGG) for both metals and sulphides, possibly controlled by grain boundary migration of olivine and/or pyroxene. Comparison of these results with geochemically constrained thermal models of the H-chondrite parent body shows an excellent correlation between average crystal sizes, and inferred depths in the original parent body, consistent with expectations based on thermal modelling. This study highlights the potential of grain-size as a quantitative marker of the degree of thermal metamorphism, although further work on a wider set of samples will be required to explore the limits of this approach.

Reference
Guignard J, Toplis MJ (2014) Textural properties of iron-rich phases in H ordinary chondrites and quantitative links to the degree of thermal metamorphism. Geochimica et Cosmochimica Acta (in Press)

Link to Article: [DOI: 10.1016/j.gca.2014.11.006]

Copyright Elsevier

¹D.S.Lauretta et al. (>10)*
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
*Find the extensive, full author and affiliation list on the publishers website

We review the results of an extensive campaign to determine the physical, geological, and dynamical properties of asteroid (101955) Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. We combine these data with cosmochemical and dynamical models to develop a hypothetical timeline for Bennu’s formation and evolution. We infer that Bennu is an ancient object that has witnessed over 4.5 Gyr of solar system history. Its chemistry and mineralogy were established within the first 10 Myr of the solar system. It likely originated as a discrete asteroid in the inner Main Belt approximately 0.7–2 Gyr ago as a fragment from the catastrophic disruption of a large (approximately 100-km), carbonaceous asteroid. It was delivered to near-Earth space via a combination of Yarkovsky-induced drift and interaction with giant-planet resonances. During its journey, YORP processes and planetary close encounters modified Bennu’s spin state, potentially reshaping and resurfacing the asteroid. We also review work on Bennu’s future dynamical evolution and constrain its ultimate fate. It is one of the most Potentially Hazardous Asteroids with an approximately 1-in-2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter. OSIRIS-REx will return samples from the surface of this intriguing asteroid in September 2023.

Reference
Lauretta DS et al. (2014) The OSIRIS-REx target asteroid (101955) Bennu: Constraints on its physical, geological, and dynamical nature from astronomical observations. Meteoritics and Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12353]

Published by arrangement with John Wiley & Sons 

^1,2,3Jemma Davidson et al. (>10)*
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
²Planetary and Space Sciences, The Open University, Milton Keynes, Buckinghamshire, UK
³Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA
*Find the extensive, full author and affiliation list on the publishers website

Here, we report the mineralogy, petrography, C-N-O-stable isotope compositions, degree of disorder of organic matter, and abundances of presolar components of the chondrite Roberts Massif (RBT) 04133 using a coordinated, multitechnique approach. The results of this study are inconsistent with its initial classification as a Renazzo-like carbonaceous chondrite, and strongly support RBT 04133 being a brecciated, reduced petrologic type >3.3 Vigarano-like carbonaceous (CV) chondrite. RBT 04133 shows no evidence for aqueous alteration. However, it is mildly thermally altered (up to approximately 440 °C); which is apparent in its whole-rock C and N isotopic compositions, the degree of disorder of C in insoluble organic matter, low presolar grain abundances, minor element compositions of Fe,Ni metal, chromite compositions and morphologies, and the presence of unequilibrated silicates. Sulfides within type I chondrules from RBT 04133 appear to be pre-accretionary (i.e., did not form via aqueous alteration), providing further evidence that some sulfide minerals formed prior to accretion of the CV chondrite parent body. The thin section studied contains two reduced CV3 lithologies, one of which appears to be more thermally metamorphosed, indicating that RBT 04133, like several other CV chondrites, is a breccia and thus experienced impact processing. Linear foliation of chondrules was not observed implying that RBT 04133 did not experience high velocity impacts that could lead to extensive thermal metamorphism. Presolar silicates are still present in RBT 04133, although presolar SiC grain abundances are very low, indicating that the progressive destruction or modification of presolar SiC grains begins before presolar silicate grains are completely unidentifiable.

Reference
Davidson J et al. (2014) Petrography, stable isotope compositions, microRaman spectroscopy, and presolar components of Roberts Massif 04133: A reduced CV3 carbonaceous chondrite. Meteoritics & Planetary Society (in Press)
Link to Article [DOI: 10.1111/maps.12377]

Published by Arrangement with John Wiley & Sons

¹Patrick H. Donohue, ¹Clive R. Neal
¹Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA

Quantitative textural analysis is a powerful tool in the investigation of basalt crystallization. We present the first comprehensive crystal size distribution analysis of Apollo 17 high-titanium lunar basalts, with a focus on ilmenite. Crystal size distributions of ilmenite, pyroxene, plagioclase, olivine and armalcolite were determined for 18 high-Ti mare basalt samples from the Apollo 17 mission. A subset of the ilmenite size distribution (size bins of <0.6mm in length) reflects growth at post-eruption or post-emplacement cooling rates. Growth of these small ilmenite crystals is controlled by cooling rate and not bulk composition or ilmenite abundance. CSD characteristics tied to cooling rate determined by experiments yield estimates of cooling rate in natural samples. Matrix ilmenite grew at rates up to 250°C/hr, while most samples contained phenocrysts that originated in environments cooling at <3°C/hr. Textural characteristics of ilmenite phenocrysts are used to develop a relative stratigraphy for the samples within a lava flow based upon comparisons with terrestrial analogues.

Reference
Donohue PH, Neal CR (2014) Quantitative textural analysis of ilmenite in Apollo 17 high-titanium mare basalts. Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.11.002]

Copyright Elsevier

¹Kathleen E. Vander Kaaden, ¹Carl B. Agee, ¹Francis M. McCubbin
¹Institute of Meteoritics, Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA

The density and compressibility of four synthetic molten lunar picritic glasses was investigated from 0-10 GPa and 1748-2473 K. The picritic glasses were collected from the lunar surface during the Apollo missions, and they are hypothesized to have rapidly quenched as glass beads during pyroclastic fire fountain eruptions. The specific melt compositions investigated in the present study are the Apollo 15 green glass Type C (A15C, TiO2 = 0.26 wt%), the Apollo 14 yellow glass (A14Y, TiO2 = 4.58 wt%), the Apollo 17 orange glass 74220-type (A17O TiO2 = 9.12 wt%), and the Apollo 14 black glass (A14B, TiO2 = 16.40 wt%). These glasses are reported to represent primary unfractionated melts, making them a prime candidate for experimental studies into lunar basalt density and compressibility during partial melting of the lunar mantle. Sink-float experiments were conducted on the synthetic molten lunar glass compositions using a piston-cylinder apparatus (P 2.5 GPa) in order to bracket the density of the melts. New sink-float data are reported for A15C, A14Y, and A17O, which are combined with previously published density and compressibility data on A15C, A17O, and A14B. Although the Ti-rich liquids are highly compressible at lower pressures, they become nearly incompressible at much higher pressures when compared to the molten low-Ti glasses. Consequently, the melts with the most TiO2 (A14B) are the least dense at higher pressures, a reversal of what is seen at lower pressures. This change in density and compressibility is attributed to changes in coordination of Ti and Fe in the silicate melt structure. As Ti4+ abundances in the silicate melt increase, predominantly [IV]Ti4+ and [IV]Fe2+ change to [VI]Ti4+ and [VI]Fe2+ in the melt structure. All of the data from the present study were used to calculate a Birch-Murnaghan equation-of-state (BM-EOS) for each melt composition. The BM-EOS model for each composition was then combined with previously published estimates for the residual mantle source mineralogy and depth of origin for each of the glasses to assess the density of the partial melt with respect to its point of origin. This information was used to determine whether or not the melt would rise or sink with respect to its source region. We determined that all melt compositions, with the exception of the A17O melt, should have been able to rise to the crust-mantle boundary as a result of buoyancy forces alone, although different mechanisms are likely required for magma ascent through the lunar crust. For the rise of A17O, other modes of ascent through the lunar mantle are required to extract this melt composition from the mantle, and volatiles are not a plausible solution on the grounds of melt density alone.

Reference
Vander Kaaden KE, Agee CB, McCubbin FM (2014) Density and compressibility of the molten lunar picritic glasses: Implications for the roles of Ti and Fe in the structures of silicate melts. Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.10.029]

Copyright Elsevier

¹Yuka Fujii, ¹Jun Kimura, ²James Dohm, ³Makiko Ohtake
¹Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan.
²The University Museum, The University of Tokyo, Tokyo, Japan.
³Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan.

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Reference
Fujii Y, Kimura J, Dohm J, Ohtake M (2014) Geology and Photometric Variation of Solar System Bodies with Minor Atmospheres: Implications for Solid Exoplanets. Astrobiology 14(9) 753-768.
Link to Article [doi:10.1089/ast.2014.1165]

¹Adam Culka, ¹Kateřina Osterrothová, ²Ian Hutchinson, ²Richard Ingley, ²Melissa McHugh, ³Aharon Oren, ⁴Howell G. M. Edward,¹Jan Jehlička
¹Institute of Geochemistry, Mineralogy, and Mineral Resources, Charles University in Prague, Prague, Czech Republic
²Department of Physics and Astronomy, University of Leicester, Leicester, UK
³Department of Plant and Environmental Sciences, The Alexander Silverman Institute of Life Sciences, The Edmond J. Safra Campus, Givat Ram, Jerusalem, Israel
⁴Division of Chemical and Forensic Sciences, University of Bradford, Bradford BD7 1DP, UK

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Reference
Culka A, Osterrothová K,Hutchinson I, Ingley R, McHugh M, Oren A, Edwards HGM, Jehlička J (2014) Research article: Detection of pigments of halophilic endoliths from gypsum: Raman portable instrument and European Space Agency’s prototype Analysis. Philosophical Transactions of the Royal Society A.,372 20140203
Link to Article [doi:10.1098/rsta.2014.0203]