^1,2David Morate, ^1,2Julia de León, ³Mário De Prá, ^1,2Javier Licandro, ^1,4Antonio Cabrera-Lavers, ⁵Humberto Campins, ⁶Noemí Pinilla-Alonso, ⁷Víctor Alí-Lagoa

¹Instituto de Astrofísica de Canarias (IAC), C/vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
²Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
³Observatório Nacional, Coordenação de Astronomia e Astrofísica, 20921-400 Rio de Janeiro, Brazil
⁴GTC Project Office, 38205 La Laguna, Tenerife, Spain
⁵Physics Department, University of Central Florida, PO Box 162385, Orlando, FL 32816-2385, USA
⁶Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, 37996 TN, USA
⁷Laboratoire Lagrange, OCA, Boulevard de l’Observatoire, BP 4229 06304 Nice Cedex 04, France

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Reference
Morate D, de León J, De Prá M, Licandro J, Cabrera-Lavers A, Campins H, Pinilla-Alonso N, Alí-Lagoa V (2016) Compositional study of asteroids in the Erigone collisional family using visible spectroscopy at the 10.4 m GTC. Astronomy & Astrophysics 586, A129
Link to Article [http://dx.doi.org/10.1051/0004-6361/201527453]

The most popular papers on Cosmochemistry Papers in February were:

1-Schwarz WH, Trieloff M, Bollinger K, Gantert N, Fernandes VA, Meyer H-P, Povenmire H, Jessberger EK, Guglielmino M, Koeberl (2016) Coeval ages of Australasian, Central American and Western Canadian tektites reveal multiple impacts 790 ka ago. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.12.037]

2-Ebert S, Bischoff A (2016) Genetic relationship between Na-rich chondrules and Ca,Al-rich inclusions? – Formation of Na-rich chondrules by melting of refractory and volatile precursors in the Solar Nebula. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2016.01.014]

3-Nguyen AN, Keller LP, Messenger S (2016) MINERALOGY OF PRESOLAR SILICATE AND OXIDE GRAINS OF DIVERSE STELLAR ORIGINS. The Astrophysical Journal 818, 51
Link to Article [http://dx.doi.org/10.3847/0004-637X/818/1/51]

4-Hutzler A et al. (2016) Description of a very dense meteorite collection area in western Atacama: Insight into the long-term composition of the meteorite flux to Earth. Meteoritics & Planetary Sciences (in Press)
Link to Article [DOI: 10.1111/maps.12607]

5-Kawasaki N,Itoh S,Sakamoto N, Yurimoto H (2016) Chronological study of oxygen isotope composition for the solar protoplanetary disk recorded in a fluffy Type A CAI from Vigarano. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.12.031]

^1,2M. Marsset, ²P. Vernazza, ^3,4M. Birlan, ⁵F. DeMeo, ⁵R. P. Binzel, ¹C. Dumas, ¹J. Milli, ^3,4M. Popescu4,3
¹European Southern Observatory (ESO), Alonso de Córdova 3107, 1900 Casilla Vitacura, Santiago, Chile
²Aix Marseille University, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
³IMCCE, Observatoire de Paris, 77 avenue Denfert-Rochereau, 75014 Paris Cedex, France
⁴Astronomical Institute of the Romanian Academy, 5 Cuţitul de Argint, 040557 Bucharest, Romania
⁵Department of Earth, Atmospheric and Planetary Sciences, MIT, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA

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Reference
Marsset M, Vernazza P, Birlan M, DeMeo F, Binzel RP, Dumas C, Milli J, Popescu M (2016) Compositional characterisation of the Themis family. Astronomy & Astrophysics 586 A15
Link to Article [http://dx.doi.org/10.1051/0004-6361/201526962]

¹C. Tubiana, ^1,2C. Snodgrass, ³R. Michelsen, ³H. Haack, ¹H. Böhnhardt, ⁴A. Fitzsimmons, ⁵I. P. Williams
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 33077 Göttingen, Germany
²Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
³Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, 1350 Copenhagen, Denmark
⁴Astrophysics Research Centre, Department of Physics and Astronomy, Queen’s University Belfast, Belfast BT7 1NN, UK
⁵School of Physics and Astronomy, Queen Mary, University of London, London E1 4NS, UK

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Reference
Tubiana C, Snodgrass C, Michelsen R, Haack H, Böhnhardt H, Fitzsimmons A, Williams IP (2016) 2P/Encke, the Taurid complex NEOs and the Maribo and Sutter’s Mill meteorites. Astronomy & Astrophysics 584, A97
Link to Article [http://dx.doi.org/10.1051/0004-6361/201425512]

¹M. Hilchenbach (>10)*
¹Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
*Find the extensive, full author and affiliation list on the publishers website

The COmetary Secondary Ion Mass Analyser instrument on board ESA’s Rosetta mission has collected dust particles in the coma of comet 67P/Churyumov–Gerasimenko. During the early-orbit phase of the Rosetta mission, particles and particle agglomerates have been imaged and analyzed in the inner coma at distances between 100 km and 10 km off the cometary nucleus and at more than 3 AU from the Sun. We identified 585 particles of more than 14 μm in size. The particles are collected at low impact speeds and constitute a sample of the dust particles in the inner coma impacting and fragmenting on the targets. The sizes of the particles range from 14 μm up to sub-millimeter sizes and the differential dust flux size distribution is fitted with a power law exponent of −3.1. After impact, the larger particles tend to stick together, spread out or consist of single or a group of clumps, and the flocculent morphology of the fragmented particles is revealed. The elemental composition of the dust particles is heterogeneous and the particles could contain typical silicates like olivine and pyroxenes, as well as iron sulfides. The sodium to iron elemental ratio is enriched with regard to abundances in CI carbonaceous chondrites by a factor from ~1.5 to ~15. No clear evidence for organic matter has been identified. The composition and morphology of the collected dust particles appear to be similar to that of interplanetary dust particles.

Reference
Hilchenbach M et al. (2016) COMET 67P/CHURYUMOV–GERASIMENKO: CLOSE-UP ON DUST PARTICLE FRAGMENTS. The Astrophysical Journal (Letters) 816, L32
Link to Article [http://dx.doi.org/10.3847/2041-8205/816/2/L32http://dx.doi.org/10.3847/2041-8205/816/2/L32]

^1,2Tuan H. Vu1, Robert Hodyss, ^1,2Mathieu Choukroun, ^1,2Paul V. Johnson
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
²NASA Astrobiology Institute

The composition of Europa’s subsurface ocean is a critical determinant of its habitability. However, our current understanding of the ocean composition is limited to its expression on the surface. This work investigates experimentally the composition of mixed sodium–magnesium–sulfate–chloride solutions when frozen to 100 K, simulating conditions that likely occur as ocean fluids are emplaced onto Europa’s surface. Micro-Raman spectroscopy is used to characterize phase composition of the frozen brines at 100 K. Our results show that solutions containing Na+, Cl−, Mg2+, and ${{\mathrm{SO}}_{4}}^{2-}$ preferentially crystallize into Na2SO4 and MgCl2 hydrated minerals upon freezing, even at elevated [Mg2+]/[Na+] ratios. The detection of epsomite (MgSO4•7H2O) on Europa’s surface, if confirmed, may thus imply a relatively sodium-poor ocean composition or a radiolytic process that converts MgCl2 to MgSO4 as suggested by Brown & Hand. The formation of NaCl on the surface, while dependent upon a number of factors such as freezing rate, may indicate an ocean significantly more concentrated in sodium than in magnesium.

Reference
Vu TH, Hodyss R, Choukroun M, Johnson PV (2016) CHEMISTRY OF FROZEN SODIUM–MAGNESIUM–SULFATE–CHLORIDE BRINES: IMPLICATIONS FOR SURFACE EXPRESSION OF EUROPA’S OCEAN COMPOSITION. The Astrophysical Journal (Letters) 816, L26
Link to Article [http://dx.doi.org/10.3847/2041-8205/816/2/L26]

¹S. Xu, ²M. Jura, ³P. Dufour, ²B. Zuckerman
¹European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching, Germany
²Department of Physics and Astronomy, University of California, Los Angeles CA 90095-1562, USA
³Institut de Recherche sur les Exoplanètes (iREx), Université de Montréal, Montréal, QC H3C 3J7, Canada

We report high-resolution spectroscopic observations of WD 1145+017—a white dwarf that was recently found to be transitted by multiple asteroid-sized objects within its tidal radius. We discovered numerous circumstellar absorption lines with linewidths of ~300 km s−1 from Mg, Ca, Ti, Cr, Mn, Fe, and Ni, possibly from several gas streams produced by collisions among the actively disintegrating objects. The atmosphere of WD 1145+017 is polluted with 11 heavy elements, including O, Mg, Al, Si, Ca, Ti, V:, Cr, Mn, Fe, and Ni. Evidently, we are witnessing the active disintegration and subsequent accretion of an extrasolar asteroid.

Reference
Xu S, Jura M, Dufour P, Zuckerman B (2016) EVIDENCE FOR GAS FROM A DISINTEGRATING EXTRASOLAR ASTEROID. The Astrophysical journal (Letters), 816 L22
Link to Article [http://dx.doi.org/10.3847/2041-8205/816/2/L22]

¹Laurence E. Nyquist, ²Chi-Yu Shih, ^1,3Francis M. McCubbin, ^3,4Alison R. Santos, ^3,4Charles K. Shearer, ²Zhan X. Peng, ^3,4Paul V. Burger,³Carl B. Agee
¹NASA Johnson Space Center, Mailcode XI, Houston, Texas, USA
²Jacobs, NASA Johnson Space Center, Houston, Texas, USA
³Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
⁴Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA

The bulk matrix domain of the Martian breccia NWA 7034 was examined petrographically and isotopically to better understand the provenance and age of the source material that make up the breccia. Both 147Sm-143Nd and 146Sm-142Nd age results for mineral separates from the bulk matrix portion of breccia NWA 7034 suggest that various lithological components in the breccia probably formed contemporaneously ~4.44 Ga ago. This old age is in excellent agreement with the upper intersection ages (4.35–4.45 Ga) for U-Pb discordia and also concordia defined by zircon and baddeleyite grains in matrix and igneous-textured clasts. Consequently, we confirm an ancient age for the igneous components that make up the NWA 7034 breccia. Substantial disturbance in the Rb-Sr system was detected, and no age significance could be gleaned from our Rb-Sr data. The disturbance to the Rb-Sr system may be due to a thermal event recorded by bulk-rock K-Ar ages of 1.56 Ga and U-Pb ages of phosphates at about 1.35–1.5 Ga, which suggest partial resetting from an unknown thermal event(s), possibly accompanying breccia formation. The NWA 7034 bulk rock is LREE enriched and similar to KREEP-rich lunar rocks, which indicates that the earliest Martian crust was geochemically enriched. This enrichment supports the idea that the crust is one of the enriched geochemical reservoirs on Mars that have been detected in studies of other Martian meteorites.

Reference
Nyquist E, Shih C-Y,McCubbin, FM,Santos AR, Shearer CK, Peng ZX, Burger PV, Agee CB (2016) Rb-Sr and Sm-Nd isotopic and REE studies of igneous components in the bulk matrix domain of Martian breccia Northwest Africa 7034. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12606]
Published by arrangement wit John Wiley & Sons

^1,2Kathryn A. Dyl et al.(>10*)
¹Department of Applied Geology, Curtin University, Perth, WA, Australia
²CSIRO Earth Sciences and Resource Engineering, Perth, WA, Australia
*Find the extensive, full author and affiliation list on the publishers website

Mason Gully, the second meteorite recovered using the Desert Fireball Network (DFN), is characterized using petrography, mineralogy, oxygen isotopes, bulk chemistry, and physical properties. Geochemical data are consistent with its classification as an H5 ordinary chondrite. Several properties distinguish it from most other H chondrites. Its 10.7% porosity is predominantly macroscopic, present as intergranular void spaces rather than microscopic cracks. Modal mineralogy (determined via PS-XRD, element mapping via energy dispersive spectroscopy [EDS], and X-ray tomography [for sulfide, metal, and porosity volume fractions]) consistently gives an unusually low olivine/orthopyroxene ratio (0.67−0.76 for Mason Gully versus ~1.3 for typical H5 ordinary chondrites). Widespread “silicate darkening” is observed. In addition, it contains a bright green crystalline object at the surface of the recovered stone (diameter ≈ 1.5 mm), which has a tridymite core with minor α-quartz and a rim of both low- and high-Ca pyroxene. The mineralogy allows the calculation of the temperatures and ƒ(O2) characterizing thermal metamorphism on the parent body using both the two-pyroxene and the olivine-chromite geo-oxybarometers. These indicate that MG experienced a peak metamorphic temperature of ~900 °C and had a similar ƒ(O2) to Kernouvé (H6) that was buffered by the reaction between olivine, metal, and pyroxene. There is no evidence for shock, consistent with the observed porosity structure. Thus, while Mason Gully has some unique properties, its geochemistry indicates a similar thermal evolution to other H chondrites. The presence of tridymite, while rare, is seen in other OCs and likely exogenous; however, the green object itself may result from metamorphism.

Reference
Dyl KA et al. (2016) Characterization of Mason Gully (H5): The second recovered fall from the Desert Fireball Network. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12605]
Published by arrangement with John Wiley & Sons

^1,2McCanta, M. C., ¹Beckett, J. R., ¹Stolper, E. M.
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
²Department of Earth and Ocean Sciences, Tufts University, Medford, Massachusetts, USA

Phosphorus zoning is observed in olivines in high-FeO (type IIA) chondrules in H chondrites over the entire range of petrologic grades: H3.1–H6. Features in P concentrations such as oscillatory and sector zoning, and high P cores are present in olivines that are otherwise unzoned in the divalent cations. Aluminum concentrations are low and not significantly associated with P zoning in chondrule olivines. In highly unequilibrated H chondrites, phosphorus zoning is generally positively correlated with Cr. Atomic Cr:P in olivine is roughly 1:1 (3:1 for one zone in one olivine in RC 075), consistent with Cr3+ charge-balancing P5+ substituting for Si4+. Normal igneous zonation involving the dominant chrome species Cr2+ was observed only in the LL3.0 chondrite Semarkona. In more equilibrated chondrites (H3.5–H3.8), Cr spatially correlated with P is occasionally observed but it is diffuse relative to the P zones. In H4–H6 chondrites, P-correlated Cr is absent. One signature of higher metamorphic grades (≥H3.8) is the presence of near matrix olivines that are devoid of P oscillatory zoning. The restriction to relatively high metamorphic grade and to grains near the chondrule–matrix interface suggests that this is a response to metasomatic processes. We also observed P-enriched halos near the chondrule–matrix interface in H3.3–H3.8 chondrites, likely reflecting the loss of P and Ca from mesostasis and precipitation of Ca phosphate near the chondrule surface. These halos are absent in equilibrated chondrites due to coarsening of the phosphate and in unequilibrated chondrites due to low degrees of metasomatism. Olivines in type IA chondrules show none of the P-zoning ubiquitous in type IIA chondrules or terrestrial igneous olivines, likely reflecting sequestration of P in reduced form within metallic alloys and sulfides during melting of type IA chondrules.

Reference
McCanta MC, Beckett JR, Stolper EM (2016) Correlations and zoning patterns of phosphorus and chromium in olivine from H chondrites and the LL chondrite Semarkona. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12604]
Published by arrangement with John Wiley & Sons