^1,2K.E. Miller, ^1,2D.S. Lauretta, ^2,3,4,5H.C. Connolly Jr., ⁶E.L. Berger, ⁷K. Nagashima, ²K. Domanik
Geochimica et Cosmochimica Acta (in Press) Link to Article [http://doi.org/10.1016/j.gca.2017.04.009]
¹Space Sciences Division, Southwest Research Institute, San Antonio, TX 78238
²Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
³Department of Geology, School of Earth and the Environment, Rowan University, 201 Mullica Hill Road, Glassboro, N. J. 08028 USA
⁴Earth and Environmental Sciences, The Graduate Center of the City University of New York, Brooklyn, NY 10016, USA
⁵Earth and Planetary Science, American Museum of Natural History, Central Park West, New York, NY 10024, USA
⁶GeoControl Systems Inc. – Jacobs JETS – NASA Johnson Space Center, Houston, TX 77058, USA
⁷Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Manoa, Honolulu, HI 96822, USA
Copyright Elsevier

Sulfide assemblages are commonly found in chondritic meteorites as small inclusions in the matrix or in association with chondrules. These assemblages are widely hypothesized to form through pre-accretionary corrosion of metal by H2S gas or through parent body processes. We report here on two unequilibrated R chondrite samples that contain large, chondrule-sized sulfide nodules in the matrix. Both samples are from Mount Prestrud (PRE) 95404. Chemical maps and spot and broad-beam electron microprobe analyses (EMPA) were used to assess the distribution, stoichiometry, and bulk composition of sulfide nodules and silicate chondrules in the clasts. Oxygen isotope data were collected via secondary ion mass spectrometry (SIMS) to assess the relationship of chondrules to other chondrite groups. Scanning electron microscopy (SEM), focused ion beam (FIB), and transmission electron microscopy (TEM) analyses were used to assess fine-scale features and identify crystal structures in sulfide assemblages. Thermodynamic models were used to assess the temperature, sulfur fugacity (fS2), total pressure, dust-to-gas ratio, and oxygen fugacity (fO2) conditions during sulfide nodule and chondrule formation.

The unequilibrated clasts include a mixture of type I and type II chondrules, as well as non-porphyritic chondrules. Chondrule oxygen isotopes overlap with ordinary-chondrite chondrules. Sulfide nodules average 200 µm in diameter, have rounded shapes, and are primarily composed of pyrrhotite, pentlandite, and magnetite. Some are deformed around chondrules in a petrologic relationship similar in appearance to compound chondrules. Both nodules and sulfides in chondrules include phosphate inclusions and Cu-rich lamellae, which suggests a genetic relationship between sulfides in chondrules and in the matrix. Ni/Co ratios for matrix and chondrule sulfides are solar, while Fe and Ni are non-solar and inversely related.

We hypothesize that sulfide nodules formed via pre-accretionary melt processes. During chondrule formation, precursors composed of a mixture of silicate and sulfide material were heated to form immiscible melt droplets, which separated and cooled to form Si-rich chondrules and S-rich nodules. Sulfide melt was stabilized by a high total pressure (∼1 atm) in a dust- or ice-enriched environment. Heating of this material contributed to a high fS2 (2 × 10-3 atm at 1138 °C), and high fO2 (IW – 1 to IW – 4), in an environment with peak temperatures between 1539 °C and 1750 °C. Oxygen isotopic compositions in this region were similar to those recorded by the LL-chondrite chondrules.

¹Raphael J. Baumgartner, ¹Marco L. Fiorentini, ²Jean-Pierre Lorand, ^3,4David Baratoux, ⁵Federica Zaccarini, ⁶Ludovic Ferrière, ⁷Marko K. Prašek,⁸Kerim Sener
Geochimica et Cosmochimica Acta (in Press) Link to Article [http://doi.org/10.1016/j.gca.2017.04.011]
¹Centre for Exploration Targeting, School of Earth Sciences, ARC Centre of Excellence for Core to Crust Fluid Systems, University of Western Australia, 6009 Crawley, Australia
²Laboratoire de Planétologie et Géodynamique de Nantes, Université de Nantes and Centre National de la Recherche Scientifique, UMR 6112 44322 Nantes, France
³Géosciences Environnement Toulouse, CNRS, IRD and University of Toulouse, 31400 Toulouse, France
⁴Institut Fondamental d’Afrique Noire Cheikh Anta Diop, 5005 Dakar, Senegal
⁵Department of Applied Geological Sciences and Geophysics, University of Leoben, 8700 Leoben, Austria
⁶Natural History Museum Vienna, 1010 Vienna, Austria
⁷McGill University, Department of Earth and Planetary Sciences, H3A 0E8, Montreal, Canada
⁸Matrix Exploration Pty Ltd, 6112 Armadale, Australia
Copyright Elsevier

¹Emily A. Pringle, ^1,2Frédéric Moynier, ^2,3Pierre Beck, ⁴Randal Paniello, ^5,6Dominik C. Hezel
Earth and Planetary Science Letters 468. 62-71 Link to Article [http://doi.org/10.1016/j.epsl.2017.04.002]
¹Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, CNRS UMR 7154, 1 rue Jussieu, 75238 Paris, France
²Institut Universitaire de France, Paris, France
³Institut d’Astrophysique et de Planétologie de Grenoble, Université Grenoble Alpes, France
⁴Department of Earth and Planetary Sciences, Washington University in St. Louis, USA
⁵University of Cologne, Department of Geology and Mineralogy, Zülpicher Str. 49b, 50674 Köln, Germany
⁶Department of Mineralogy, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
Copyright Elsevier

¹Ryuji Okazaki, ^2,3Keisuke Nagao
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12819]
¹Faculty of Sciences, Department of Earth and Planetary Sciences, Kyushu University, Nishi-ku, Fukuoka, Japan
²Graduate School of Science, Geochemical Research Center, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
³Korea Polar Research Institute, Incheon, Yeonsu-gu, South Korea
Published by arrangement with John Wiley & Sons

The Sutter’s Mill (SM) CM chondrite fell in California in 2012. The CM chondrite group is one of the most primitive, consisting of unequilibrated minerals, but some of them have experienced complex processes occurring on their parent body, such as aqueous alteration, thermal metamorphism, brecciation, and solar wind implantation. We have determined noble gas concentrations and isotopic compositions for SM samples using a stepped heating gas extraction method, in addition to mineralogical observation of the specimens. The primordial noble gas abundances, especially the P3 component trapped in presolar diamonds, confirm the classification of SM as a CM chondrite. The mineralogical features of SM indicate that it experienced mild thermal alteration after aqueous alteration. The heating temperature is estimated to be 500 °C. The variation in the heating temperature of thermal alteration is consistent with the texture as a breccia. The heterogeneous distribution of solar wind noble gases is also consistent with it. The cosmic-ray exposure (CRE) age for SM is calculated to be 0.059 ± 0.023 Myr based on cosmogenic 21Ne by considering trapped noble gases as solar wind, the terrestrial atmosphere, P1 (or Q), P3, A2, and G components. The CRE age lies at the shorter end of the CRE age distribution of the CM chondrite group.

^1,2,3Tomáš Kohout et al (>10)*
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12871]
¹Department of Physics, University of Helsinki, Finland
²Institute of Geology, The Czech Academy of Sciences, Praha, Czech Republic
³Finnish Fireball Network, Finland
*Find the extensive, full author and affiliation list on the publishers website
Published by arrangement with John Wiley & Sons

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short-lived radionuclides are compatible with an atmospheric pre-entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The 10Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre-entry radius.

¹A. J. King, ¹P. F. Schofield, ¹S. S. Russell
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12872]
¹Department of Earth Sciences, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The CM carbonaceous chondrite meteorites experienced aqueous alteration in the early solar system. They range from mildly altered type 2 to almost completely hydrated type 1 chondrites, and offer a record of geochemical conditions on water-rich asteroids. We show that CM1 chondrites contain abundant (84–91 vol%) phyllosilicate, plus olivine (4–8 vol%), magnetite (2–3 vol%), Fe-sulfide (120 °C), although higher water/rock ratios may also have played a role. The modal data provide constraints for interpreting the composition of asteroids and the mineralogy of samples returned from these bodies. We predict that “CM1-like” asteroids, as has been proposed for Bennu—target for the OSIRIS-REx mission—will have a high abundance of Mg-rich phyllosilicates and Fe-oxides, but be depleted in calcite.

¹Randy L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12869]
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

This report presents bulk composition data for 10 lunar meteorite stones from Oman for which the names have been approved since June, 2012. On the basis of composition and reported find location, four new meteorites are represented among this group of stones. Data from neutron activation analysis of 371 subsamples of all lunar meteorites from Oman and Saudi Arabia analyzed in this laboratory are presented.

¹Mokkapati Shyam Prasad, ¹N. G. Rudraswami, ¹Agnelo A. De Araujo, ¹Vijay D. Khedekar
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12858]
¹CSIR-National Institute of Oceanography, Dona Paula, Goa, India
Published by arrangement with John Wiley & Sons

Fe-Ni metal is a common constituent of most meteorites and is an indicator of the thermal history of the respective meteorites, it is a diagnostic tool to distinguish between groups/subgroups of meteorites. In spite of over a million micrometeorites collected from various domains, reports of pure metallic particles among micrometeorites have been extremely rare. We report here the finding of a variety of cosmic metal particles such as kamacite, plessite, taenite, and Fe-Ni beads from deep-sea sediments of the Indian Ocean, a majority of which have entered the Earth unaffected by frictional heating during atmospheric entry. Such particles are known as components of meteorites but have never been found as individual entities. Their compositions suggest precursors from a variety of meteorite groups, thus providing an insight into the metal fluxes on the Earth. Some particles have undergone heating and oxidation to different levels during entry developing features similar to I-type cosmic spherules, suggesting atmospheric processing of individual kamacites/taenite grains as another hitherto unknown source for the I-type spherules. The particles have undergone postdepositional aqueous alteration transforming finally into the serpentine mineral cronstedtite. Aqueous alteration products of kamacite reflect the local microenvironment, therefore they have the potential to provide information on the composition of water in the solar nebula, on the parent bodies or on surfaces of planetary bodies. Our observations suggest it would take sustained burial in water for tens of thousands of years under cold conditions for kamacites to alter to cronstedtite.

^1,2Alan E. Rubin, ³Chi Ma
Chemie der Erde – Geochemistry (in Press) Link to Article [http://doi.org/10.1016/j.chemer.2017.01.005]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA
²Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, USA
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
Copyright Elsevier

¹Andrew S. Rivkin, ²Ellen S. Howell, ³Joshua P. Emery, ⁴Jessica Sunshine
Icarus (in Press) Link to Article [http://doi.org/10.1016/j.icarus.2017.04.006]
¹Johns Hopkins University Applied Physics Laboratory, 11101 Johns Hopkins Rd, Laurel MD, 20723 USA 443-778-2811
²University of Arizona, Lunar and Planetary Laboratory
³University of Tennessee
⁴University of Maryland
Copyright Elsevier

Water and hydroxyl, once thought to be found only in the primitive airless bodies that formed beyond roughly 2.5-3 AU, have recently been detected on the Moon and Vesta, which both have surfaces dominated by evolved, non-primitive compositions. In both these cases, the water/OH is thought to be exogenic, either brought in via impacts with comets or hydrated asteroids or created via solar wind interactions with silicates in the regolith or both. Such exogenic processes should also be occurring on other airless body surfaces. To test this hypothesis, we used the NASA Infrared Telescope Facility (IRTF) to measure reflectance spectra (2.0 to 4.1 μm) of two large near-Earth asteroids (NEAs) with compositions generally interpreted as anhydrous: 433 Eros and 1036 Ganymed. OH is detected on both of these bodies in the form of absorption features near 3 μm. The spectra contain a component of thermal emission at longer wavelengths, from which we estimate thermal of 167±98 J m−2s−1/2K−1 for Eros (consistent with previous estimates) and 214±80 J m−2s−1/2K−1 for Ganymed, the first reported measurement of thermal inertia for this object. These observations demonstrate that processes responsible for water/OH creation on large airless bodies also act on much smaller bodies.