¹S. N. Teplyakova, ¹C. A. Lorenz, ¹M. A. Ivanova, ¹N. N. Kononkova, ¹M. O. Anosova, ¹K. M. Ryazantsev, ¹Yu. A. Kostitsyn
Geochemistry International 56, 1-13 Link to Article [DOI
https://doi.org/10.1134/S0016702918010081]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia

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¹Quentin Charbonnier, ^1,2Frédéric Moynier, ¹Julien Bouchez
Science Bulletin 63, 385-394 Link to Article [https://doi.org/10.1016/j.scib.2018.01.018]
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 and Université Paris Diderot, 75231 Paris, France

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¹Yang Liu
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2018.04.010]
¹Lunar and Planetary Institute, Universities Space Research Association, Houston, TX, USA

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^1,2Arshad Ali, ²Iffat Jabeen, ¹Sobhi J. Nasir, ²Neil R. Banerjee
Geosciences 8, 15 Link to Article [doi:10.3390/geosciences8010015]
¹Earth Sciences Research Centre (ESRC), Sultan Qaboos University (SQU), Al-Khodh, Muscat 123, Oman
²Department of Earth Sciences, Western University, 1151 Richmond Street N., London, ON N6A 5B7, Canada

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^1,2Zhiyong Xiao,^1,3Zhaoxu Chenac, ¹Jiang Pua, ¹Xiao Xiao, ¹Yichen Wang, ¹Jun Huang
Geomorphology 306, 128-140 Link to Article [https://doi.org/10.1016/j.geomorph.2018.01.020]
¹Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, Hubei Province, China
²Space Science Institute, Macau University of Science and Technology, Macau, China
³College of Earth Sciences, Jilin University, Changchun, Jilin Province, China

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¹T. A. Gornostaeva, ¹A. V. Mokhov, ¹P. M. Kartashov, ¹O. A. Bogatikov
Petrology 26, 82-95 Link to Article [DOI
https://doi.org/10.1134/S0869591118010046]
¹Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM)Russian Academy of Sciences, Moscow, Russia

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¹K. Righter, ²K. Pando, ³M. Humayun, ³N. Waeselmann, ³S. Yang, ¹A. Boujibar, ²L.R. Danielson
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.04.011]
¹NASA JSC, Mailcode XI2, 2101 NASA Pkwy, Houston, TX 77058
²Jacobs JETS Contract, NASA JSC, Houston, TX 77058
³National High Magnetic Field Laboratory, Florida State Univ., Tallahassee, FL 32310
Copyright Elsevier

Earth’s core contains ∼10% of a light element that may be a combination of Si, S, C, O or H, with Si potentially being the major light element. Metal-silicate partitioning of siderophile elements can place important constraints on the P-T-fO2 and composition of the early Earth, but the effect of Si alloyed in Fe liquids is unknown for many of these elements. In particular, the effect of Si on the partitioning of highly siderophile elements (Au, Re and PGE) is virtually unknown. To address this gap in understanding, we have undertaken a systematic study of the highly siderophile elements Au, Pd, and Pt, and the volatile siderophile elements P, Ga, Cu, Zn, and Pb at variable Si content of metal, and 1600 °C and 1 GPa. From our experiments we derive epsilon interaction parameters between these elements and Si in Fe metallic liquids. The new parameters are used to update an activity model for trace siderophile elements in Fe alloys; Si causes large variation in the magnitude of activity coefficients of these elements in FeSi liquids. Because the interaction parameters are all positive, Si causes a decrease in their metal/silicate partition coefficients. We combine these new activity results with experimental studies of Au, Pd, Pt, P, Ga, Cu, Zn and Pb, to derive predictive expressions for metal/silicate partition coefficients which can then be applied to Earth. The expressions are applied to two scenarios for continuous accretion of Earth; specifically for constant and increasing fO2 during accretion. The results indicate that mantle concentrations of P, Ga, Cu, Zn, and Pb can be explained by metal-silicate equilibrium during accretion of the Earth where Earth’s early magma ocean deepens to pressures of 40-60 GPa. Au, Pd, and Pt, on the other hand become too high in the mantle in such a scenario, and require a later removal mechanism, rather than an addition as traditionally argued. A late reduction event that removes 0.5% metal from a shallow magma ocean can lower the Au, Pd, and Pt contents to values near the current day BSE. On the other hand, removal of 0.2 to 1.5% of a late sulfide-rich matte to the core would lower the Au, Pd, and Pt concentrations in the mantle, but not to chondritic relative concentrations observed in the BSE. If sulfide matte is called upon to remove HSEs, they must be later added via a late veneer to re-establish the high and chondritic relative PUM concentrations. These results suggest that although accretion and core formation (involving a Si, S, and C-bearing metallic liquid) were the primary processes establishing many of Earth’s mantle volatile elements and HSE, a secondary removal process is required to establish HSEs at their current and near-chondritic relative BSE levels. Mn and P – two siderophile elements that are central to biochemical processes (photosynthesis and triphosphates, respectively) – have significant and opposite interactions with FeSi liquids, and their mantle concentrations would be notably different if Earth had a Si-free core.

¹A.Frigeri et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.04.019]
¹Istituto Nazionale di Astrofisica (INAF), Istituto di Astrofisica e Planetologia Spaziali (IAPS), Via Fosso del Cavaliere 100, Rome, Italy
Copyright Elsevier

This article presents the spectral parameter maps used in this Surface Composition of Ceres Special Issue. The definition and use of spectral parameters has always played a fundamental role in understanding the properties and composition of a planetary surface. Mapping proper spectral parameters, shows the global mineralogical diversity across Ceres. In this work, we discuss the production process of Ceres spectral parameter maps derived by the data of the Visible and Infrared mapping spectrometer onboard NASA’s Dawn mission. We describe the data processing of the VIR spectra and the procedure to retrieve the geometries (latitude, longitude and illumination angles) of the acquired data. Spectra and geometries are used to project and mosaic this data to produce Geographic Information System-compatible spectral parameters maps of Ceres. An overview of the variability of the data across the quadrangles is given, addressing the specific analysis to each quadrangle mapping paper included in this special issue.

¹S. Ackiss, ¹B. Horgan, ²F. Seelos, ³W. Farrand, ⁴J. Wray
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.03.026]
¹Purdue University, Department of Earth, Atmospheric, and Planetary Sciences, 550 Stadium Mall Drive, West Lafayette, Indiana 47907
²Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723
³Space Science Institute, 4750 Walnut St #205, Boulder, Colorado 80301
⁴Georgia Institute of Technology, School of Earth & Atmospheric Sciences, 311 Ferst, Drive Atlanta, Georgia 30332
Copyright Elsevier

Here we examine the mineral assemblages detected on possible glaciovolcanic edifices in the Sisyphi Planum region of Mars, a high-latitude region in the southern highlands nestled between the Argyre and Hellas impact basins. Minerals were identified utilizing visible/near-infrared spectra from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Analysis of eleven CRISM images located on the volcanic edifices revealed three distinct spectral classes in the region which are interpreted to be: gypsum-dominated, smectite-zeolite- iron oxide-dominated (possibly palagonite), and polyhydrated sulfate-dominated material. While sulfates can form under a variety of alteration conditions, palagonite-like mineral assemblages require low-temperature and high water-to-rock hydrothermal conditions typically found in subglacial or subaqueous volcanic eruptions. The possible palagonite detections on the volcanic edifices, the geomorphology of the region, and the analogous terrestrial mineralogy of subglacial eruptions strongly suggests the formation of these minerals during subglacial eruptions or associated hydrothermal systems. This implies that thick water ice sheets were present in this region in the late Noachian or early Hesperian, and that the subglacial hydrothermal systems could have supported habitable environments with excellent biosignature preservation potential.

^1,2Mikael Granvik,^3,4Peter Brown
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.04.012]
¹Department of Physics, University of Helsinki, P.O. Box 64, 00014, Finland
²Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Box 848, S-98128, Sweden
³Department of Physics and Astronomy, University of Western Ontario, London, N6A 3K7, Canada
⁴Centre for Planetary Science and Exploration, University of Western Ontario, London, N6A 5B7, Canada
Copyright Elsevier

Over the past decade there has been a large increase in the number of automated camera networks that monitor the sky for fireballs. One of the goals of these networks is to provide the necessary information for linking meteorites to their pre-impact, heliocentric orbits and ultimately to their source regions in the solar system. We re-compute heliocentric orbits for the 25 meteorite falls published to date from original data sources. Using these orbits, we constrain their most likely escape routes from the main asteroid belt and the cometary region by utilizing a state-of-the-art orbit model of the near-Earth-object population, which includes a size-dependence in delivery efficiency. While we find that our general results for escape routes are comparable to previous work, the role of trajectory measurement uncertainty in escape-route identification is explored for the first time. Moreover, our improved size-dependent delivery model substantially changes likely escape routes for several meteorite falls, most notably Tagish Lake which seems unlikely to have originated in the outer main belt as previously suggested. We find that reducing the uncertainty of fireball velocity measurements below  ∼ 0.1 km/s does not lead to reduced uncertainties in the identification of their escape routes from the asteroid belt and, further, their ultimate source regions. This analysis suggests that camera networks should be optimized for the largest possible number of meteorite recoveries with measured speed precisions of order 0.1 km/s.