¹Motoo Ito et al. (>10)*
¹Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
*Find the extensive, full author and affiliation list on the publishers Website

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Reference
Ito M et al. (2014) H, C, and N isotopic compositions of Hayabusa category 3 organic samples. Earth, Planets and Space  66, 91
Link to Article [doi:10.1186/1880-5981-66-91]

¹Michelle S Thompson, ²Roy Christoffersen, ¹Thomas J Zega, ³Lindsay P Keller
¹ Lunar and Planetary Laboratory, University of Arizona, 1629 E University Blvd, Tucson, AZ 85721, USA
²Jacobs, NASA Johnson Space Center, Mail Code KR, Houston, TX 77058,USA
³NASA JSC Mail Code KR, Houston, TX 77058, USA

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Reference
Thompson MS, Christofferson R, Zega TJ, Keller LP (2014) Microchemical and structural evidence for space weathering in soils from asteroid Itokawa. Earth, Planets and Space 66, 89
Link to Article [doi:10.1186/1880-5981-66-89]

¹Micah J. Schaible, ¹Raúl A. Baragiola
¹Laboratory of Atomic and Surface Physics, University of Virginia, Charlottesville, VA

Hydroxyl on the lunar surface revealed by remote measurements has been thought to originate from solar wind hydrogen implantation in the regolith. The hypothesis is tested here through experimental studies of the rate and mechanisms of OH bond formation due to H+ implantation of amorphous SiO2 and olivine in ultrahigh vacuum. The samples were implanted with 2–10 keV H+, in the range of solar wind energies and the OH absorption band at ~2.8 µm measured by transmission FTIR spectroscopy. For 2 keV protons in SiO2, the OH band depth saturated at fluences F ~5 × 1016 H+/cm2 to a maximum 0.0032 absorption band depth, corresponding to a column density ηs = 1.1 × 1016 OH/cm2. The corresponding values for 5 keV protons in olivine are > 2 × 1017/cm2, 0.0067 and 4.0 × 1016 OH/cm2. The initial conversion rate of implanted H+ into hydroxyl species was found to be ~90% and decreased exponentially with fluence. There was no evidence for molecular water formation due to proton irradiation. Translating the laboratory measurements in thin plate samples to the granular lunar regolith, it is estimated that the measurements can account for a maximum of 17% relative OH absorption in reflectance spectroscopy of mature soils, consistent with spacecraft observations in the infrared of the Moon.

Reference
Schaible MJ, Baragiola RA (2014) The role of solar wind in SiOH bond formation on the surfaces of airless bodies in space. Journal of Geophysical Research: Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004650]

Published by arrangement with John Wiley & Sons

^1,6Kereszturi, A., ²Blumberger, Z., ³Józsa, S., ⁴May, Z., ⁵Müller, A., ⁵Szabó, M. ⁵Tóth, M.
¹Research Center for Astronomy and Earth Sciences, Konkoly Thege Miklós Astronomical Institute, Astrophysical and Geochemical Laboratory, Hungarian Academy of Sciences, Budapest, Hungary
²Eotvos Lorand University of Sciences, Faculty of Science, Centre of Environmental Sciences, Hungarian Academy of Sciences, Budapest, Hungary
³Faculty of Science, Department of Petrology and Geochemistry, Eotvos Lorand University of Sciences, Hungarian Academy of Sciences, Budapest, Hungary
⁴Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary
⁵Research Center for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, Hungarian Academy of Sciences, Budapest, Hungary
⁶NASA Astrobiology Institute; Thermodynamics, Disequilibrium and Evolution Focus Group

Analysis of the NWA 2086 CV3 chondrite showed a matrix/chondrule ratio of 52%, similar to Bali, Mokoia, and Grosanaja. Nearly twice as many chondrule fragments as intact ones demonstrate that an early fragmentation phase occurred prior to final accretion. After this event, no substantial mechanical change or redeposition is evident. Rims with double-layered structures were identified around some chondrules, which, in at least one case, is attributed to an accretionary origin. The rim’s outer parts with a diffuse appearance were formed by in situ chemical alteration. During this later process, Mg content decreased, Fe content increased, and olivine composition was homogenized, producing a rim composition close to that of the matrix. This alteration occasionally happened along fractures and at confined locations, and was probably produced by fluid interactions. Iron oxides are the best candidate for a small grain-sized alteration product; however, technical limitations in the available equipment did not allow exact phase identification. These results suggest that NWA 2086 came from a location (possible more deeply buried) in the CV parent body than Mokoia or Bali, and suffered less impact effects—although there is no evidence of sustained thermal alteration. This meteorite may represent a sample of the CV parent asteroid interior and provide a useful basis for comparison with other CV meteorites in the future.

Reference
Kereszturi A, Blumberger Z, Józsa S, May Z, Müller A, Szabó M, Tóth M (2014) Alteration processes in the CV chondrite parent body based on analysis of NWA 2086 meteorite. Meteoritics & Planetary Science (in Press).
Link to Article [doi: 10.1111/maps.12336]

Published by arrangement with John Wiley & Sons

¹Ennis, M. E., ¹McSween, H. Y.
^1,2Department of Earth and Planetary Sciences, Planetary Geoscience Institute, University of Tennessee, Knoxville, Tennessee, USA

Crystal size distribution (CSD) and spatial distribution pattern (SDP) analyses are applied to the early crystallizing phases, olivine and pyroxene, in olivine-phyric shergottites (Elephant moraine [EET] 79001A, Dar al Gani [DaG] 476, and dhofar [Dho] 019) from each sampling locality inferred from Mars ejection ages. Trace element zonation patterns (P and Cr) in olivine are also used to characterize the crystallization history of these Martian basalts. Previously reported 2-D CSDs for these meteorites are re-evaluated using a newer stereographically corrected methodology. Kinks in the olivine CSD plots suggest several populations that crystallized under different conditions. CSDs for pyroxene in DaG 476 and EET 79001A reveal single populations that grew under steady-state conditions; pyroxenes in Dho 019 were too intergrown for CSD analysis. Magma chamber residence times of several days for small grains to several months for olivine megacrysts are calculated using the CSD slopes and growth rates inferred from previous experimental data. Phosphorus imaging in olivines in DaG 476 and Dho 019 indicate rapid growth of skeletal, sector-zoned, or patchy cores, probably in response to delayed nucleation, followed by slow growth, and finally rapid dendritic growth with back-filling to form oscillatory zoning in rims. SPD analyses indicate that olivine and pyroxene crystals grew or accumulated in clusters rather than as randomly distributed grains. These data reveal complex solidification histories for Martian basalts, and are generally consistent with the formation at depth of olivine megacryst cores, which were entrained in ascending magmas that crystallized pyroxenes, small olivines, and oscillatory rims on megacrysts.

Reference
Ennis ME, McSween HY (2014) Crystallization kinetics of olivine-phyric shergottites. Meteoritics & Planetary Science (in Press)
Link to Article [doi: 10.1111/maps.12349]

Copyright Elsevier

¹Andrew J. Westphal et al. (>10)*
¹Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA, USA.
*Find the extensive, full author and affiliation list on the publishers Website

Seven particles captured by the Stardust Interstellar Dust Collector and returned to Earth for laboratory analysis have features consistent with an origin in the contemporary interstellar dust stream. More than 50 spacecraft debris particles were also identified. The interstellar dust candidates are readily distinguished from debris impacts on the basis of elemental composition and/or impact trajectory. The seven candidate interstellar particles are diverse in elemental composition, crystal structure, and size. The presence of crystalline grains and multiple iron-bearing phases, including sulfide, in some particles indicates that individual interstellar particles diverge from any one representative model of interstellar dust inferred from astronomical observations and theory.

Reference
Westphal AJ et al. (2014) Evidence for interstellar origin of seven dust particles collected by the Stardust spacecraft. Science 345, 6198, 786-791
Link to Article [DOI: 10.1126/science.1252496]

Reprinted with permission from AAAS

¹Ben Rozitis,¹Eric MacLennan,¹Joshua P. Emery
¹Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA

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Reference
Rozitis B, MacLennan E, Emery JP (2014) Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA. Nature 512, 174–176
Link to Article [doi:10.1038/nature13632]

¹Joachim Audouard, ¹François Poulet, ¹Mathieu Vincendon, ¹Jean‐Pierre Bibring, ¹Brigitte Gondet, ¹Yves Langevin, ²Ralph E. Milliken, ³Denis Jouglet

¹Institut d’Astrophysique Spatiale (UPSUD/CNRS), Orsay, France
²Dept. Geological Sciences, Brown University, Providence, RI, U.S.A.
³CNES, Toulouse, France

Here we discuss one of the current reservoirs of water on Mars, the regolith and rocks exposed at the surface. This reservoir is characterized by the presence of H2O- and OH-bearing phases that produce a broad absorption at a wavelength of ~3 µm in near-infrared (NIR) reflectance spectra. This absorption is present in every ice-free spectrum of the Martian surface obtained thus far by orbital NIR spectrometers. We present a quantitative analysis of the global distribution of the 3 µm absorption using the Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA) imaging spectrometer that has been mapping the surface of Mars at kilometer scale for more than ten years. Based on laboratory reflectance spectra of a wide range of hydrous minerals and phases, we estimate a model-dependent water content of 4 ± 1 wt. % in the equatorial and mid-latitudes. Surface hydration increases with latitude, with an asymmetry in water content between the northern and southern hemispheres. The surface hydration is compared to various parameters (albedo, dust, geological units, time, relative humidity, atmospheric water pressure, and in situ measurements performed by Phoenix and Curiosity) to constrain the nature of the reservoir. We conclude that the nature of the surface hydration of the Martian low latitudes is not adsorbed water but rather more tightly-bound water molecules and hydroxyl groups in the structure of the materials of the near-top surface. A frost-related process best explains the implementation of water into and onto the first microns of the high latitudes Martian regolith.

Reference
Audouard J, Poulet F, Vincendon M, Bibring J-P, Gondet B, Langevin Y, Milliken RE, Jouglet D (2014) Water in the Martian regolith from OMEGA/Mars Express. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2014JE004649]

Published by arrangement with John Wiley & Sons

¹D.L.Blaney et al. (>10)*
¹Jet Propulsion Laboratory, Pasadena, California Institute of Technology, CA, USA
*Find the extensive, full author and affiliation list on the publishers Website

A suite of eight rocks analyzed by the Curiosity Rover while it was stopped at the Rocknest sand ripple show the greatest chemical divergence of any potentially sedimentary rocks analyzed in the early part of the mission. Relative to average martian soil and to the stratigraphically lower units encountered as part of the Yellowknife Bay formation, these rocks are significantly depleted in MgO, with a mean of 1.3 wt %, and high in Fe, averaging over 20 wt % FeOT. with values between 15 – 26 wt% FeOT. The variable iron and low magnesium, and rock texture make it unlikely that these are igneous rocks. Rock surface textures range from rough to smooth, can be pitted or grooved, and show various degrees of wind erosion. Some rocks display poorly defined layering while others seem to show possible fractures. Narrow vertical voids are present in Rocknest-3, one of the rocks showing the strongest layering. Rocks in the vicinity of Rocknest may have undergone some diagenesis similar to other rocks in the Yellowknife Bay Formation as indicated by the presence of soluble calcium phases. The most reasonable scenario is that fine-grained sediments, potentially a mixture of feldspar-rich rocks from Bradbury Rise and normal martian soil, was lithified together by an iron-rich cement.

Reference
Blaney DL et al. (2014) Chemistry and texture of the rocks at Rocknest, Gale Crater: Evidence for sedimentary origin and diagenetic Alteration. Journal of Geophysical Research Planets (in Press)
Link to Article [doi: 10.1002/2013JE004590]

Published by arrangement with John Wiley & Sons

^1,2Ian A. Crawford, ³Katherine H. Joy
¹Department of Earth and Planetary Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK
²Centre for Planetary Sciences at UCL/Birkbeck, Gower Street, London WC1E 6BT, UK
³School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester M13 9PL, UK

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Reference
Crawford IA, Joy KH (2014) Lunar exploration: opening a window into the history and evolution of the inner Solar System. Philosophical Transactions of the Royal Society A13, 372, 2024
Link to Article [doi:10.1098/rsta.2013.0315]