¹Caio Vinícius Gabrig Turbay Rangel, ²Marcos Tadeu D’Azeredo Orlando, ³Cláudio De Morisson Valeriano, ⁴Alexandre de Oliveira Chaves
International Geology Review 59, 1966-1973 Link to Article [https://doi.org/10.1080/00206814.2017.1308842]
¹Geology Department, Universidade Federal do Espirito Santo, Alegre, Brasil
²Department of Physics, Universidade Federal do Espirito Santo, Alegre, Brasil
³TECTO, Universidade do Estado Rio de Janiero, Rio de Janiero, Brazil
⁴ICG, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

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¹A.B.Verchovsky
Geochemistry International 55, 957-970 Link to Article [https://doi.org/10.1134/S0016702917110106]
¹School of Physical Sciences STEM, The Open University, Walton Hall Milton Keynes United Kingdom

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¹Bruno L. do Nascimento-Dias,^1,2Davi F. de Oliveira,²Alessandra S. Machado,²Olga M.O. Araújo,²Ricardo T. Lopes,²Marcelino J. dos Anjos
X-Ray Spectrometry 47, 86-91 Link to Article [DOI: 10.1002/xrs.2815]
¹Physics Institute Armando Dias Tavares, University of State of Rio de Janeiro, Rio de Janeiro, Brazil
²Nuclear Instrumentation Laboratory, PEN, COPPE, UFRJ, Rio de Janeiro, Brazil

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^1,2H.Zhang et al. (>10)
Applied Physics Letters 111, 184104 Link to Article [https://doi.org/10.1063/1.5010050]
¹State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
²University of Chinese Academy of Sciences, Beijing 100049, China

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^1,2T Loylip, ^2,3S Wannawichian
Journal of Physics: Conference Series 901, 012005 Link to Article [https://doi.org/10.1088/1742-6596/901/1/012005]
¹Graduate School, Chiang Mai University, Chiang Mai, Thailand
²National Astronomical Research Institute of Thailand (NARIT), Chiang Mai, Thailand
³Department of physics and Materials Science, Chiang Mai University, Chiang Mai, Thailand

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¹Jean-Philippe Combe et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.12.039]
¹Bear Fight Institute, 22 Fiddler’s Road, P.O. Box 667, Winthrop, WA 98862, USA
Copyright Elsevier

We studied the surface composition of Ceres within the limits of the Ezinu quadrangle in the ranges 180 – 270°E and 21 – 66°N by analyzing data from Dawn’s visible and near-infrared data from the Visible and InfraRed mapping spectrometer and from multispectral images from the Framing Camera. Our analysis includes the distribution of hydroxylated minerals, ammoniated phyllosilicates, carbonates, the search for organic materials and the characterization of physical properties of the regolith. The surface of this quadrangle is largely homogenous, except for small, high-albedo carbonate-rich areas, and one zone on dark, lobate materials on the floor of Occator, which constitute the main topics of investigation. 1) Carbonate-rich surface compositions are associated with H2O ice rich crust. Weaker absorption bands of hydroxylated and ammoniated minerals over the carbonate-rich areas can be explained by higher abundances of carbonates at the topmost surface. 2) Dark, smooth lobate materials at the foot of Occator’s northeastern wall possibly reveal fresh slumping of phyllosilicate-rich materials with fine grain size, or local enrichment in carbon-rich materials such as tholins. 3) The deeper absorption band depth of OH and NH4, on the rim of several impact craters, is one observation that is consistent with a stratification of the phyllosilicate abundance that has been inferred previously from global investigations.

^1,2M.Devogèle et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.12.026]
¹Université de Liège, Space sciences, Technologies and Astrophysics Research (STAR) Institute, Allée du 6 Août 19c, Sart Tilman, 4000 Liège, Belgium
²Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange UMR7293, Nice, France
Copyright Elsevier

Asteroids can be classified into several groups based on their spectral reflectance. Among these groups, the one belonging to the L-class in the taxonomic classification based on visible and near-infrared spectra exhibit several peculiar properties. First, their near-infrared spectrum is characterized by a strong absorption band interpreted as the diagnostic of a high content of the FeO bearing spinel mineral. This mineral is one of the main constituents of Calcium-Aluminum-rich Inclusions (CAI) the oldest mineral compounds found in the solar system. In polarimetry, they possess an uncommonly large value of the inversion angle incompatible with all known asteroid belonging to other taxonomical classes. Asteroids found to possess such a high inversion angle are commonly called Barbarians based on the first asteroid on which this property was first identified, (234) Barbara. In this paper we present the results of an extensive campaign of polarimetric and spectroscopic observations of L-class objects. We have derived phase-polarization curves for a sample of 7 Barbarians, finding a variety of inversion angles ranging between 25 and 30°. Spectral reflectance data exhibit variations in terms of spectral slope and absorption features in the near-infrared. We analyzed these data using a Hapke model to obtain some inferences about the relative abundance of CAI and other mineral compounds. By combining spectroscopic and polarimetric results, we find evidence that the polarimetric inversion angle is directly correlated with the presence of CAI, and the peculiar polarimetric properties of Barbarians are primarily a consequence of their anomalous composition.

¹J.J. Bellucci, ^1,2A.A. Nemchin, ¹M.J. Whitehouse, ¹J.F. Snape, ²P. Bland, ²G.K. Benedix, ³J. Roszjar
Earth and Planetary Science Letters 485, 79-87 Link to Article [https://doi.org/10.1016/j.epsl.2017.12.039]
¹Department of Geosciences, Swedish Museum of Natural History, SE-104 05, Stockholm, Sweden
²Department of Applied Geology, Curtin University, Perth, WA 6845, Australia
³Department of Mineralogy and Petrography, Natural History Museum Vienna, Burgring 7, 1010, Vienna, Austria
Copyright Elsevier

The initial Pb compositions of one enriched shergottite, one intermediate shergottite, two depleted shergottites, and Nakhla have been measured by Secondary Ion Mass Spectrometry (SIMS). These values, in addition to data from previous studies using an identical analytical method performed on three enriched shergottites, ALH 84001, and Chassigny, are used to construct a unified and internally consistent model for the differentiation history of the Martian mantle and crystallization ages for Martian meteorites. The differentiation history of the shergottites and Nakhla/Chassigny are fundamentally different, which is in agreement with short-lived radiogenic isotope systematics. The initial Pb compositions of Nakhla/Chassigny are best explained by the late addition of a Pb-enriched component with a primitive, non-radiogenic composition. In contrast, the Pb isotopic compositions of the shergottite group indicate a relatively simple evolutionary history of the Martian mantle that can be modeled based on recent results from the Sm–Nd system. The shergottites have been linked to a single mantle differentiation event at 4504 Ma. Thus, the shergottite Pb isotopic model here reflects a two-stage history 1) pre-silicate differentiation (4504 Ma) and 2) post-silicate differentiation to the age of eruption (as determined by concordant radiogenic isochron ages). The μ-values (²³⁸U/²⁰⁴Pb) obtained for these two different stages of Pb growth are μ₁ of 1.8 and a range of μ₂ from 1.4–4.7, respectively. The μ₁-value of 1.8 is in broad agreement with enstatite and ordinary chondrites and that proposed for proto Earth, suggesting this is the initial μ-value for inner Solar System bodies. When plotted against other source radiogenic isotopic variables (Sr_i, γ¹⁸⁷Os, ε¹⁴³Nd, and ε¹⁷⁶Hf), the second stage mantle evolution range in observed mantle μ  -values display excellent linear correlations (r²>0.85) and represent a spectrum of Martian mantle mixing-end members (depleted, intermediate, enriched).

^1,2Yunzhao Wu, ³Bruce Hapke
Earth and Planetary Science Letters 484, 145-153 Link to Article [https://doi.org/10.1016/j.epsl.2017.12.003]
¹Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210034, China
²Space Science Institute, Macau University of Science and Technology, Macau, China
³Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA, USA
Copyright Elsevier

The Moon’s reflectance spectrum records many of its important properties. However, prior to Chang’E-3 (CE-3), no spectra had previously been measured on the lunar surface. Here we show the in situ reflectance spectra of the Moon acquired on the lunar surface by the Visible-Near Infrared Spectrometer (VNIS) onboard the CE-3 rover. The VNIS detected thermal radiation from the lunar regolith, though with much shorter wavelength range than typical thermal radiometer. The measured temperatures are higher than expected from theoretical model, indicating low thermal inertia of the lunar soil and the effects of grain facet on soil temperature in submillimeter scale. The in situ spectra also reveal that 1) brightness changes visible from orbit are related to the reduction in maturity due to the removal of the fine and weathered particles by the lander’s rocket exhaust, not the smoothing of the surface and 2) the spectra of the uppermost soil detected by remote sensing exhibit substantial differences with that immediately beneath, which has important implications for the remote compositional analysis. The reflectance spectra measured by VNIS not only reveal the thermal, compositional, and space-weathering properties of the Moon but also provide a means for the calibration of optical instruments that view the surface remotely.

^1,2Philip J.Carter, ¹Zoë M.Leinhardt, ³Tim Elliott, ²Sarah T.Stewart, ³Michael J.Walter
Earth and Planetary Science Letters 484, 276-286 Link to Article [https://doi.org/10.1016/j.epsl.2017.12.012]
¹School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK
²Department of Earth and Planetary Sciences, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
³School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, UK
Copyright Elsevier

Geochemical studies of planetary accretion and evolution have invoked various degrees of collisional erosion to explain differences in bulk composition between planets and chondrites. Here we undertake a full, dynamical evaluation of ‘crustal stripping’ during accretion and its key geochemical consequences. Crusts are expected to contain a significant fraction of planetary budgets of incompatible elements, which include the major heat producing nuclides. We present smoothed particle hydrodynamics simulations of collisions between differentiated rocky planetesimals and planetary embryos. We find that the crust is preferentially lost relative to the mantle during impacts, and we have developed a scaling law based on these simulations that approximates the mass of crust that remains in the largest remnant. Using this scaling law and a recent set of N-body simulations of terrestrial planet formation, we have estimated the maximum effect of crustal stripping on incompatible element abundances during the accretion of planetary embryos. We find that on average approximately one third of the initial crust is stripped from embryos as they accrete, which leads to a reduction of ∼20% in the budgets of the heat producing elements if the stripped crust does not reaccrete. Erosion of crusts can lead to non-chondritic ratios of incompatible elements, but the magnitude of this effect depends sensitively on the details of the crust-forming melting process on the planetesimals. The Lu/Hf system is fractionated for a wide range of crustal formation scenarios. Using eucrites (the products of planetesimal silicate melting, thought to represent the crust of Vesta) as a guide to the Lu/Hf of planetesimal crust partially lost during accretion, we predict the Earth could evolve to a superchondritic 176Hf/177Hf (3–5 parts per ten thousand) at present day. Such values are in keeping with compositional estimates of the bulk Earth. Stripping of planetary crusts during accretion can lead to detectable changes in bulk composition of lithophile elements, but the fractionation is relatively subtle, and sensitive to the efficiency of reaccretion.