¹Driss Takir, ¹Joshua P. Emery, ¹Harry Y. McSween Jr.
¹Department of Earth and Planetary Sciences and Planetary Geosciences Institute, University of Tennessee, Knoxville, TN 37996, United States

Proposed mineralogical linkages between CM/CI carbonaceous chondrites and outer Main Belt asteroids remain uncertain due to a dearth of diagnostic absorptions in visible and near-infrared (∼0.4 to 2.5 μm) spectra of the two sets of objects. Absorptions near 3 μm in both sets hold promise for illuminating the potential linkages. Spectral comparisons of meteorites and asteroids have been challenging because meteorite spectra have usually been acquired in ambient terrestrial environments, and hence were contaminated by atmospheric water. In this study, we compare near-infrared spectra of chondrites measured in the laboratory under asteroid-like conditions (Takir et al. 2013) and spectra of asteroids measured with the long-wavelength cross-dispersed (LXD: 1.9-4.2-μm) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF) (Takir and Emery 2012). Using the 3-μm band shape, we find that spectral Group 2 CM and CI (Ivuna) chondrites are possible meteorite analogs for asteroids with the sharp 3-μm features, which are predominately located in the 2.5 < a < 3.3 AU region. Spectral Group 2 CM chondrites contain phyllosilicate phases intermediate between endmembers Fe-serpentine and Mg-serpentine, with a petrological subtype ranging from 2.2 to 2.1 (Takir et al. 2013). No meteorite match was found for asteroids showing a rounded 3-μm feature, which tend to be located farther from the Sun (3.0 < a < 4.0 AU), or for asteroids with distinctive spectra like 1 Ceres or 52 Europa. The study of the 3-μm band in meteorites and asteroids has implications for the understanding of phyllosilicate mineralogy and its distribution in the outer Main Belt region.

Reference
Takir D, EmeryJP, McSween Jr. HY (2015) Toward an Understanding of Phyllosilicate Mineralogy in the Outer Main Asteroid Belt. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.042]
Copyright Elsevier

¹Nazarov, M.A., ¹Shornikov, S.I., ¹Demidova, S.I.
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, Russian Federation

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Reference
Nazarov MA, Shornikov SI, Demidova SI (2015) Origin of native silicon and iron silicides in the Dhofar 280 lunar Meteorite. Petrology 23, 168-175
Link to Article [DOI: 10.1134/S0869591115020071]

¹Demidova, S.I., ¹Nazarov, M.A., ²Ntaflos, T., ³Brandstätter, F.
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, Russian Federation
²Department für Lithosphärenforschung, Universität Wien, Althanstrasse 14, Wien, Austria
³Naturhistorisches Museum, Burgring 7, Wien, Austria

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Reference
Demidova SI, Nazarov MA, Ntaflo T, Brandstätter F (2015) Possible serpentine relicts in lunar meteorites.
Petrology 23, 116-126
Link to Article [DOI: 10.1134/S0869591115020034]

¹Badyukov, D.D., ²Raitala, J., ²Kostama, P., ³Ignatiev, A.V. 
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, Russian Federation
²Department of Physics, University of Oulu, PO Box 3600, Oulu, Finland
³Far East Geological Institute, Far East Branch, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159, Vladivostok, Russian Federation

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Reference
Badyukov DD, Raitala J, Kostama P, Ignatiev AV (2015) Chelyabinsk meteorite: Shock metamorphism, black veins and impact melt dikes, and the Hugoniot. Petrology 23, 103-115
Link to Article [DOI: 10.1134/S0869591115020022]

¹Ivanova, M.A., ² Petaev, M.I. 
¹Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, 19 Kosygin St., Moscow, Russian Federation
²Harvard University Department of Earth and Planetary Sciences and Department of Solar, Stellar and Planetary Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States

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Reference
Ivanova MA, Petaev MI (2015) Characteristics and origin of the components of the carbonaceous chondrite NWA 470. Petrology 23, 150-167.
Link to Article [DOI: 10.1134/S0869591115020058]

¹Pati, J.K., ^2,3Reimold, W.U, ²Greshake, A., ²Schmitt, R.T., ^4,5Koeberl, C., ¹Pati, P., ¹Prakash, K
¹Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Allahabad, India
²Museum für Naturkunde Berlin, Invalidenstrasse 43, Berlin, Germany
³Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin, Germany
⁴Department of Lithospheric Research, University of Vienna, Althanstrasse 14, Vienna, Austria
⁵Natural History Museum, Burgring 7, Vienna, Austria

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Reference
Pati JK, Reimold WU, Greshake A, Schmitt RT, Koeberl C, Pati P, Prakash K (2015) Pseudotachylitic breccia from the Dhala impact structure, north-central India: Texture, mineralogy and geochemical characterization. Tectonophysics 649 18-32
Link to Article [DOI: 10.1016/j.tecto.2015.01.021]

¹Elizabeth C. Sklute, ¹Timothy D. Glotch, ²Jennifer L. Piatek, ¹William R. Woerner, ¹Alexis A. Martone, ¹Meredith L. Kraner
¹Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, U.S.A.
²Department of Physics and Earth Sciences, Central Connecticut State University, New Britain, Connecticut 06050, U.S.A.

The hydroxy sulfate jarosite [(K,Na,H3O)Fe3(SO4)2(OH)6] has both been discovered on Mars, and is associated with areas of highly acidic runoff on Earth. Because jarosite is extremely sensitive to formation conditions, it is an important target mineral for remote sensing applications. Yet at visible and near infrared (VNIR) wavelengths, where many spacecraft spectrometers collect data, the spectral abundance of a mineral in a mixture is not linearly correlated with the surface abundance of that mineral. Radiative transfer modeling can be used to extract quantitative abundance estimates if the optical constants (the real and imaginary indices of refraction, n and k) for all minerals in the mixture are known. Unfortunately, optical constants for a wide variety of minerals, including sulfates like jarosite, are not available. This is due, in part, to the inherent difficulty in obtaining such data for minerals that tend to crystallize naturally as fine-grained (~10 μm) powders, like many sulfates including jarosite. However, the optical constants of powders can be obtained by inverting the equation of radiative transfer and using it to model laboratory spectra. In this paper, we provide robust n and k data for synthetic potassium, hydronium, and sodium jarosite in the VNIR. We also explicitly describe the calculation procedures (including access to our Matlab code) so that others may obtain optical constants of additional minerals. Expansion of the optical constants library in the VNIR will facilitate the extraction of quantitative mineral abundances, leading to more in-depth evaluations of remote sensing target locations.

Reference
Sklute EC, Glotch TD, Piatek JL, Woerner WR, Martone AA, Kraner ML (2015) Optical constants of synthetic potassium, sodium, and hydronium jarosite. American Mineralogist 100, 1110-1122
Link to Article [doi: 10.2138/am-2015-4824]

Copyright: The Mineralogical Society of America

¹N.G. Rudraswami, ¹M. Shyam Prasad, ^1,2K. Nagashima, ³R.H. Jones
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
²Hawaii Institute of Geophysics and Planetology, Hawai‘i at Māanoa, 1680 East-West-Road, Honolulu, HI 96822, USA
³Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA

Most olivine relict grains in cosmic spherules selected for the present study are pristine and have not been disturbed during their atmospheric entry, thereby preserving their chemical, mineralogical and isotopic compositions. In order to understand the origin of the particles, oxygen isotope compositions of relict olivine grains in twelve cosmic spherules collected from deep sea sediments of the Indian Ocean were studied using secondary ion mass spectrometry. Most of the data lie close to the CCAM (Carbonaceous Chondrite Anhydrous Mineral) line, with Δ17O ranging from –5 to 0‰. The data overlap oxygen isotopic compositions of chondrules from carbonaceous chondrites such as CV, CK, CR and CM, which suggests that chondrules from carbonaceous chondrites are the source of relict grains in cosmic spherules. Chemical compositions of olivine in cosmic spherules are also very similar to chondrule olivine from carbonaceous chondrites. Several olivine relict grains in three cosmic spherules are 16O-rich (Δ17O –21.9 to –18.7‰), similar to oxygen isotopic compositions observed in calcium aluminium rich inclusions (CAIs), amoeboid olivine aggregates (AOAs), and some porphyritic chondrules from carbonaceous chondrites. These grains appear to have recorded the initial oxygen isotopic composition of the inner solar nebula. Three olivine grains from two cosmic spherules have δ18O values > +20‰, which could be interpreted as mixing with stratospheric oxygen during atmospheric entry.

Reference
Rudraswami NG, Shyam Prasad M, Nagashima K, Jones RH (2015) Oxygen isotopic composition of relict olivine grains in cosmic spherules: Links to chondrules from carbonaceous chondrites. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.05.004]

Copyright Elsevier

¹Shohei Kaneko, ^1,2Masaaki Miyahara, ^1,3Eiji Ohtani, ⁴Tomoko Arai, ⁵Naohisa Hirao,⁶Kazuhisa Sato
¹Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
²Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan
³V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Science, 630090 Novosibirsk, Russia
⁴Planetary Exploration Research Center, Chiba Institute of Technology, Chiba 275-0016, Japan
⁵Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo, Hyogo 679-5198, Japan
⁶Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan * E-mail: miyahara@hiroshima-u.ac.jp

High-pressure polymorphs recovered in terrestrial craters are evidence of meteoroid impact events on the Earth’s surface. Despite countless impact craters on the Moon, high-pressure polymorphs have not been reported to date in returned Apollo samples. On the other hand, recent studies report that the high-pressure polymorphs of silica, coesite, and stishovite occur in shocked lunar meteorites. We investigated regolith breccia 15299, which was returned by the Apollo 15 mission, using the combined techniques of focused ion beam (FIB), synchrotron X-ray diffraction (XRD), and transmission electron microscopy (TEM). The regolith breccia 15299 studied here consists of a mafic impact melt breccia with millimeter-sized, coarse-grained, low-Ti basalt clasts. The mafic melt breccia consists of fragments of minerals (olivine, pyroxene, plagioclase, silica, and ilmenite) and glass. Several quartz, tridymite, and cristobalite grains of 10–100 μm across occur in the mafic impact melt breccia. Vesicular melt veins of less than ~200 μm wide cut across the mafic melt breccia matrix and mineral fragments. Some silica grains are entrained in the melt veins. One of the silica grains entrained in the melt veins consist of stishovite [a = 4.190(1), c = 2.674(1) Å, V = 46.95 Å3, space group P42/mnm] along with tridymite and silica glass. This is the first report of high-pressure polymorphs from returned lunar samples. TEM images show that the stishovite is needle-like in habit, and up to ~400 nm in size. Considering the lithologies and shock features of 15299, it is inferred that the stishovite possibly formed by the Imbrium impact or subsequent local impact event(s) in the Procellarum KREEP Terrane (PKT) of the nearside of the Moon.

Reference
Kaneko S, Miyahara M, Ohtani E, Arai T, Hirao N, Sato K (2015) Discovery of stishovite in Apollo 15299 sample.
American Mineralogist 100, 1308-1311
Link to Article [doi: 10.2138/am-2015-5290]

Copyright: The Mineralogical Society of America

¹Larry G. Evans et al. (>10)*
¹Computer Sciences Corporation, Lanham-Seabrook, MD 20706, USA

Orbital measurements obtained by the MESSENGER Gamma-Ray Spectrometer have been analyzed to determine the surface abundance of chlorine in Mercury’s northern hemisphere. The derived Cl/Si mass ratio is 0.0057 ± 0.001, which for an assumed Si abundance of 24.6 wt% corresponds to 0.14 ± 0.03 wt% Cl. The abundance of Cl is a factor of 2.9 ± 1.3 higher in the north polar region (>80° N) than at latitudes 0°−60° N, a latitudinal variation similar to that observed for Na. Our reported Cl abundances are consistent with measured bulk concentrations of neutron-absorbing elements on Mercury, particularly those observed at high northern latitudes. The Cl/K ratio on Mercury is chondritic, indicating a limited impact history akin to that of Mars, which accreted rapidly. Hypotheses for the origin of Mercury’s high metal-to-silicate ratio must be able to reproduce Mercury’s observed elemental abundances, including Cl. Chlorine is also an important magmatic volatile, and its elevated abundance in the northern polar region of Mercury indicates that it could have played a role in the production, ascent, and eruption of flood volcanic material in this region. We have identified several candidate primary mineralogical hosts for Cl on Mercury including the halide minerals lawrencite (FeCl2), sylvite (KCl), and halite (NaCl), as well as Cl-bearing alkali sulfides. Amphiboles, micas, apatite, and aqueously-deposited halides, in contrast, may be ruled out as mineralogical hosts of Cl on Mercury.

Reference
Evans LG et al. (2015) Chlorine on the Surface of Mercury: MESSENGER Gamma-Ray Measurements and Implications for the Planet’s Formation and Evolution. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.039]

Copyright Elsevier