¹Charles K. Shearer, ¹Stephen M. Elardo, ²Noah E. Petro, ³Lars E. Borg,¹Francis M. McCubbin
¹Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A.
²NASA, Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A.
³Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California 94550, U.S.A.

The Mg-suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation. This review examines the mineralogy, geochemistry, petrology, chronology, and the planetary-scale distribution of this suite of highlands plutonic rocks, presents models for their origin, examines petrogenetic relationships to other highlands rocks, and explores the link between this style of magmatism and early stages of lunar differentiation. Of the models considered for the origin of the parent magmas for the Mg-suite, the data best fit a process in which hot (solidus temperature at ≥2 GPa = 1600 to 1800 °C) and less dense (ρ ~3100 kg/m3) early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn. Some decompressional melting would occur, but placing a hot cumulate horizon adjacent to the plagioclase-rich primordial crust and KREEP-rich lithologies (at temperatures of

Reference
Shearer CK, Elardo SM, Petro NE, Borg LE, McCubbin FM (2015) Origin of the lunar highlands Mg-suite: An integrated petrology, geochemistry, chronology, and remote sensing perspective. American Mineralogist, 100,294-325
Link to Article [doi: 10.2138/am-2015-4817]

Copyright: The Mineralogical Society of America

^1,4Michael J. Gaffey, ^2,4Vishnu Reddy, ^1,4Sherry-Fieber-Beyer ³Edward Cloutis
¹Space Studies Department, John D. Odegard School of Aerospace Sciences, University of North Dakota, Grand Forks, ND 58202-9008
²Planetary Science Institute, 1700 E Fort Lowell Rd, Suite 106, Tucson, AZ 85719
³Department of Geography, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba, Canada R3B 2E9
⁴Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement No. NNX-08AE38A with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program

During a survey of the S-type asteroids, Gaffey et al. (1993) identified asteroid (354) Eleonora as anomalous with a 1 μm absorption feature ∼2.5 times stronger than any S-asteroid of comparable size. Subsequent investigation revealed significant differences in the 1 μm absorption feature between the visible & very near-infrared CCD spectra (λ < ∼1.0 μm) and other spectral data sets for this asteroid. There were also significant spectral differences among the several CCD survey spectra (SMASS-I, SMASS-II & S3OS2) of Eleonora. These differences could potentially arise from spectral variations across the asteroid surface, from observational phase angle differences, from surface temperature differences, from viewing geometry for a nonspherical body, or from the use of standard stars with deviated to different degrees from a true solar standard.

In June 2011 asteroid (354) Eleonora was observed over two nights using the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatory in order to test these possible scenarios and to better understand the nature and history of Eleonora and its relationships to other asteroids and to the meteorites. Analysis of this data set has eliminated the following options as the cause of the differences in the 1 μm absorption feature within the CCD data sets and between the CCD data sets and the other spectral data: (1) rotational spectral variations; (2) variation in surface composition with latitude; (3) observation phase; (4) surface temperature variations with differing heliocentric distance in the asteroid’s elliptical orbit; (5) spectral effects of viewing geometry for a nonspherical body; and (6) differences in spectral standard stars. We conclude that none of the CCD spectra of (354) Eleonora are reliable, and that within the limits of their spectral coverage, analyses of the three CCD spectra would produce significantly different – and generally unreliable – indications of surface mineralogy. An effort needs to be made to determine whether “bad” CCD spectra are rare with the case of (354) Eleonora being an uncommon occurrence or whether there is a broader problem with the CCD asteroid survey data sets, and if so, how to identify the “bad” spectra..

While CCD Survey spectra show apparently irreconcilable differences, the near-infrared spectra of (354) Eleonora from various observers show only minor differences, primarily in the overall spectral slope, most of which can be attributed to slight differences in the standard stars used to calibrate the data.

In June 2011, 226 near-infrared (∼0.76 – 2.5 μm) spectra of (354) Eleonora were obtained using the SpeX instrument on the NASA Infrared Telescope Facility at Mauna Kea Observatory. These spectra were consistent with the six sets of NIR spectra obtained for Eleonora by previous observers. The primary variation observed in this new data set was an approximately 10% variation in spectral slope between ∼0.8 μm and ∼1.6 μm during the rotation period of the asteroid.

Mineralogically diagnostic spectral parameters extracted from this new data are most consistent with a surface assemblage of fine-grained intimately mixed olivine (∼60-70%, ∼Fo61-71) and low nickel (<∼7-8% Ni) NiFe metal. The Fo estimate is consistent with previous estimates (Fo66±5) by Sanchez et al. (2014), but not with the estimate (∼Fo90) of Sunshine et al. (2007). The surface assemblage appears to contain a small component (∼8-10%) of igneous pyroxene (weakly constrained at ∼Fs50Wo10). The parent lithology of the surface regolith may be similar to a pallasite assemblage, although none of the three known types of pallasites are good mineralogical matches.

Reference
Gaffey MJ, Reddy V, Sherry-Fieber-Beyer, Cloutis E (2014)Asteroid (354) eleonora: Plucking an odd duck. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.12.036]

Copyright Elsevier

^1,2Grevesse, N., ³Scott, P., ⁴Asplund, M. ⁵Sauval, A.J
¹Centre Spatial de Liège, Université de Liège, avenue Pré AilyAngleur-Liège, Belgium
²Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 août, 17, B5CLiège, Belgium
³Department of Physics, Imperial College London, Blackett Laboratory, Prince Consort RoadLondon, United Kingdom
⁴Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd.Weston Creek, ACT, Australia
⁵Observatoire Royal de Belgique, avenue circulaire, 3Bruxelles, Belgium

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Grevesse N , Scott P, Asplund M, Sauval AJ (2014) The elemental composition of the Sun III. The heavy elements Cu to Th.
Astronomy and Astrophysics 573
Link to Article [DOI: 10.1051/0004-6361/201424111]

^1,2Usui, T., ²Jones, J. H. ²Mittlefehldt, D. W.
¹Astromaterials Research & Exploration Science Directorate, Johnson Space Center, NASA, Houston, Texas, USA
²Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, Japan

Melting experiments of a synthesized, alkali-bearing, H-chondrite composition were conducted at ambient pressure with three distinct oxygen fugacity conditions (IW-1, IW, and IW+2). Oxygen fugacity conditions significantly influence the compositions of partial melts. Partial melts at IW-1 are distinctly enriched in SiO2 relative to those of IW and IW+2 melts. The silica-enriched, reduced (IW-1) melts are characterized by high alkali contents and have silica-oversaturated compositions. In contrast, the silica-depleted, oxidized (≥IW) melts, which are also enriched in alkali contents, have distinctly silica-undersaturated compositions. These experimental results suggest that alkali-rich, felsic, asteroidal crusts as represented by paired achondrites Graves Nunataks 06128 and 06129 should originate from a low-degree, relatively reduced partial melt from a parent body having near-chondritic compositions. Based on recent chronological constraints and numerical considerations as well as our experimental results, we propose that such felsic magmatism should have occurred in a parent body that is smaller in size and commenced accreting later than those highly differentiated asteroids having basaltic crusts and metallic cores.

Reference
Usui T, Jones, JH, Mittlefehldt DW (2015) A partial melting study of an ordinary (H) chondrite composition with application to the unique achondrite Graves Nunataks 06128 and 06129. Meteoritics & Planetary Science (in Press)
Link to Article [doi: 10.1111/maps.12392]

Published by arrangement with John Wiley&Sons

¹K. Righter, ²L. R. Danielson, ²K. M. Pando, ³J. Williams, ³M. Humayun, ⁴R. L. Hervig, ⁴T. G. Sharp4
¹Mailcode KT, NASA Johnson Space Center, Houston, Texas, USA
²Jacobs Technology, JETS, NASA Johnson Space Center, Houston, Texas, USA
³National High Magnetic Field Laboratory and Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, Florida, USA
⁴ASU School of Earth and Space Exploration, Tempe, Arizona, USA

Highly siderophile elements (HSEs) can be used to understand accretion and core formation in differentiated bodies, due to their strong affinity for FeNi metal and sulfides. Coupling experimental studies of metal–silicate partitioning with analyses of HSE contents of Martian meteorites can thus offer important constraints on the early history of Mars. Here, we report new metal–silicate partitioning data for the PGEs and Au and Re across a wide range of pressure and temperature space, with three series designed to complement existing experimental data sets for HSE. The first series examines temperature effects for D(HSE) in two metallic liquid compositions—C-bearing and C-free. The second series examines temperature effects for D(Re) in FeO-bearing silicate melts and FeNi-rich alloys. The third series presents the first systematic study of high pressure and temperature effects for D(Au). We then combine our data with previously published partitioning data to derive predictive expressions for metal–silicate partitioning of the HSE, which are subsequently used to calculate HSE concentrations of the Martian mantle during continuous accretion of Mars. Our results show that at midmantle depths in an early magma ocean (equivalent to approximately 14 GPa, 2100 °C), the HSE contents of the silicate fraction are similar to those observed in the Martian meteorite suite. This is in concert with previous studies on moderately siderophile elements. We then consider model calculations that examine the role of melting, fractional crystallization, and sulfide saturation/undersaturation in establishing the range of HSE contents in Martian meteorites derived from melting of the postcore formation mantle. The core formation modeling indicates that the HSE contents can be established by metal–silicate equilibrium early in the history

Reference
Righter K, Danielson LR, Pando KM, Williams J, Humayun M, Hervig RL, Sharp TG (2015) Highly siderophile element (HSE) abundances in the mantle of Mars are due to core formation at high pressure and temperature. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12393]

Published by arrangement with John Wiley&Sons

^1,2Shuying Yang, ^1,2Munir Humayun, ³Kevin Righter, ^1,4Gwendolyn Jefferson, ^1,5Dana Fields, ⁶Anthony J. Irving
¹National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA
²Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, Florida, USA
³National Aeronautics and Space Administration, Johnson Space Center, Houston, Texas, USA
⁴Carter High School, Rialto, California, USA
⁵Rickards High School, Tallahassee, Florida, USA
⁶Department of Earth & Space Sciences, University of Washington, Seattle, Washington, USA

Elemental abundances for volatile siderophile and chalcophile elements for Mars inform us about processes of accretion and core formation. Such data are few for Martian meteorites, and are often lacking in the growing number of desert finds. In this study, we employed laser ablation inductively coupled plasma–mass spectrometry (LA-ICP-MS) to analyze polished slabs of 15 Martian meteorites for the abundances of about 70 elements. This technique has high sensitivity, excellent precision, and is generally accurate as determined by comparisons of elements for which literature abundances are known. However, in some meteorites, the analyzed surface is not representative of the bulk composition due to the over- or underrepresentation of a key host mineral, e.g., phosphate for rare earth elements (REE). For other meteorites, the range of variation in bulk rastered analyses of REE is within the range of variation reported among bulk REE analyses in the literature. An unexpected benefit has been the determination of the abundances of Ir and Os with a precision and accuracy comparable to the isotope dilution technique. Overall, the speed and small sample consumption afforded by this technique makes it an important tool widely applicable to small or rare meteorites for which a polished sample was prepared. The new volatile siderophile and chalcophile element abundances have been employed to determine Ge and Sb abundances, and revise Zn, As, and Bi abundances for the Martian mantle. The new estimates of Martian mantle composition support core formation at intermediate pressures (14 ± 3 GPa) in a magma ocean on Mars.

Reference
Yang S, Humayun M, Righter K, Jefferson G, Fields D, Irving AJ (2015) Siderophile and chalcophile element abundances in shergottites: Implications for Martian core Formation. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12384]

Published by Arrangement with John Wiley&Sons

¹Miriam Sharp, ²Kevin Righter,¹Richard J. Walker
¹Department of Geology, University of Maryland, College Park, Maryland, USA
²NASA Johnson Space Center, Houston, Texas, USA

This study uses experimentally determined plagioclase-melt D values to estimate the trace element concentrations of Sr, Hf, Ga, W, Mo, Ru, Pd, Au, Ni, and Co in a crystallizing lunar magma ocean at the point of plagioclase flotation. Similarly, experimentally determined metal-silicate partition experiments combined with a composition model for the Moon are used to constrain the concentrations of W, Mo, Ru, Pd, Au, Ni, and Co in the lunar magma ocean at the time of core formation. The metal-silicate derived lunar mantle estimates are generally consistent with previous estimates for the concentration of these elements in the lunar mantle. Plagioclase-melt derived concentrations for Sr, Ga, Ru, Pd, Au, Ni, and Co are also consistent with prior estimates. Estimates for Hf, W, and Mo, however, are higher. These elements may be concentrated in the residual liquid during fractional crystallization due to their incompatibility. Alternatively, the apparent enrichment could reflect the inappropriate use of bulk anorthosite data, rather than data for plagioclase separates.

Reference
Sharp M, Righter K, Walker RJ (2014) Estimation of trace element concentrations in the lunar magma ocean using mineral- and metal-silicate melt partition coefficients. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12396]

Published by arrangement with John Wiley&Sons

^1,2Elmar Buchner, ³Martin Schmieder
¹HNU – Neu-Ulm University, Wileystraße 1, D-89231 Neu-Ulm, Germany
²Institut für Mineralogie und Kristallchemie, Universität Stuttgart, Azenbergstraße 18, 70174 Stuttgart, Germany
³Philamlife Village, Pueblo de Oro, Upper Carmen, Cagayan de Oro, 9000 Philippines

The ∼24 km Nördlinger Ries and the ∼3.8 km Steinheim Basin in southern Germany are thought to represent a ∼14.8 Ma old impact crater doublet. The complex craters of the Steinheim Basin with its crater fill deposits and the Nördlinger Ries and its voluminous impact ejecta blanket are still widely preserved. Although located in an environmental setting that presumably underwent the same erosional history as the Ries crater, field geologic studies suggest that no proximal or distal ejecta of the Steinheim impact event are presently preserved. Generally, the lack of the ejecta blanket around the crater could be explained either by intense erosion, the scarcity of outcrops, or it never formed. In contrast to the lack of ejecta, fluvial and lacustrine Middle Miocene sediments deposited prior to, synchronous with, and shortly after the impact are preserved in many places in the surroundings of to the Steinheim Basin.

On low-density asteroids or planets with highly porous target rocks (⩾ 30-40% effective porosity), impact structures can form without significant ejecta outside the craters due to the compaction of porosity and a concordant drastic reduction of the ejecta velocity. In the Steinheim area, the target rocks comprised loose, porous Miocene sands, Upper Jurassic limestones and Middle Jurassic porous sand- and claystones. The average porosity of the entire sedimentary target suite may have reached 20-30% or even higher values assuming the existence of open karst cavities in the Upper Jurassic carbonates. Compaction of the porous target rocks, resulting in the reduction of ejected material, in combination with erosion could explain the apparent lack of impact ejecta in the wider periphery of the Steinheim impact structure.

Reference
Buchner E, Schmieder M (2015) The Steinheim Basin impact crater (SW-Germany) – where are the ejecta? Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.12.026]

Copyright Elsevier

¹Uwe Fink
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Az, 85721

The Single scattering albedos (SSA’s) determined for 9P /Tempel 1 are interpreted in terms of the Hapke model of irregular particle scattering efficiencies. Absorption coefficients versus wavelength from 0.31 to 2.5 μm are obtained. It is shown that the colors and exceedingly low reported SSA’s in the UV region of the spectrum below 0.4 μm cannot be reproduced with the geometric Hapke scattering model for irregular particles. However, by increasing the reported SSA’s by a small amount, absorption coefficients for particle radii of 10-100 μm vs. wavelength from 0.31 to 2.5 μm can be fitted. Several reasons are given for slightly increasing the SSA’s, such as neglect of the effects of porosity, having a more complex phase function for the particles, uncertainties in the absolute calibration and the uncertainties associated with the complex treatment of surface roughness. The absorption coefficients determined show good agreement with potential surface constituents Mg rich olivine and pyroxene with some amount of darkening iron or organic component.

Reference
Fink U (2015) Considerations regarding the Colors and low Surface Albedo of Comets using The Hapke Methodology. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.12.018]

Copyright Elsevier

^1,4Chaitanya Giri, ¹Fred Goesmann, ²Andrew Steele, ^1,3Thomas Gautier, ¹Harald Steininger, ¹Harald Krüger, ⁴Uwe J. Meierhenrich
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd, Washington DC 20015, USA
³NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴Université Nice Sophia Antipolis, Institut de Chimie de Nice, UMR 7272 CNRS, F-06108 Nice, France

We currently do not have a copyright agreement with this publisher and cannot display the abstract here
Reference
Giri C, Fred Goesmanna, Steele A, Gautier T, Steininger H, Krüger H, Meierhenrich UJ (2014) Competence evaluation of COSAC flight spare model mass spectrometer: In preparation of arrival of Philae lander on comet 67P/Churyumov-Gerasimenko. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2014.12.017]