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
We currently do not have a copyright agreement with this publisher and cannot display the abstract here
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.
1,2Bethany L. Ehlmann, 2Robert Hodyss, 3Thomas F. Bristow, 1George R. Rossman, 4,5Eleonora Ammannito M., 6Cristina De Sanctis, 5Carol A. Raymond
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13103]
1Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
3Exobiology Branch, NASA Ames Research Center, Moffett Field, California, USA
4Department of Earth Planetary and Space Sciences, University of California, Los Angeles, California, USA
5Italian Space Agency (ASI), , Rome, Italy
6Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, , Rome, Italy
Published by arrangement with John Wiley & Sons
Mg‐phyllosilicate‐bearing, dark surface materials on the dwarf planet Ceres have NH4‐bearing materials, indicated by a distinctive 3.06 μm absorption feature. To constrain the identity of the Ceres NH4‐carrier phase(s), we ammoniated ground particulates of candidate materials to compare their spectral properties to infrared data acquired by Dawn’s Visible and Infrared (VIR) imaging spectrometer. We treated Mg‐, Fe‐, and Al‐smectite clay minerals; Mg‐serpentines; Mg‐chlorite; and a suite of carbonaceous meteorites with NH4‐acetate to exchange ammonium. Serpentines and chlorites showed no evidence for ammoniation, as expected due to their lack of exchangeable interlayer sites. Most smectites showed evidence for ammoniation by incorporation of NH4+ into their interlayers, resulting in the appearance of absorptions from 3.02 to 3.08 μm. Meteorite samples tested had weak absorptions between 3.0 and 3.1 μm but showed little clear evidence for enhancement upon ammoniation, likely due to the high proportion of serpentine and other minerals relative to expandable smectite phases or to NH4+ complexing with organics or other constituents. The wavelength position of the smectite NH4 absorption showed no variation between IR spectra acquired under dry‐air purge at 25 °C and under vacuum at 25 °C to −180 °C. Collectively, data from the smectite samples show that the precise center wavelength of the characteristic ~3.05 μm v3 absorption in NH4 is variable and is likely related to the degree of hydrogen bonding of NH4‐H2O complexes. Comparison with Dawn VIR spectra indicates that the hypothesis of Mg‐saponite as the ammonium carrier phase is the simplest explanation for observed data, and that Ceres dark materials may be like Cold Bokkeveld or Tagish Lake but with proportionally more Mg‐smectite.
1Rona Oran, 1Benjamin P. Weiss, 2Ofer Cohen
Earth and Planetary Science Letters 492, 222-231 Link to Article [https://doi.org/10.1016/j.epsl.2018.02.013]
1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
2Lowell Center for Space Science and Technology, University of Massachusetts, Lowell, MA 01854, USA
Copyright Elsevier
Chondritic meteorites have been traditionally thought to be samples of undifferentiated bodies that never experienced large-scale melting. This view has been challenged by the existence of post-accretional, unidirectional natural remanent magnetization (NRM) in CV carbonaceous chondrites. The relatively young inferred NRM age [∼10 million years (My) after solar system formation] and long duration of NRM acquisition (1–106 y) have been interpreted as evidence that the magnetizing field was that of a core dynamo within the CV parent body. This would imply that CV chondrites represent the primitive crust of a partially differentiated body. However, an alternative hypothesis is that the NRM was imparted by the early solar wind. Here we demonstrate that the solar wind scenario is unlikely due to three main factors: 1) the magnitude of the early solar wind magnetic field is estimated to be <0.1 μT in the terrestrial planet-forming region, 2) the resistivity of chondritic bodies limits field amplification due to pile-up of the solar wind to less than a factor of 3.5 times that of the instantaneous solar wind field, and 3) the solar wind field likely changed over timescales orders of magnitude shorter than the timescale of NRM acquisition. Using analytical arguments, numerical simulations and astronomical observations of the present-day solar wind and magnetic fields of young stars, we show that the maximum mean field the ancient solar wind could have imparted on an undifferentiated CV parent body is <3.5 nT, which is 3–4 and 3 orders of magnitude weaker than the paleointensities recorded by the CV chondrites Allende and Kaba, respectively. Therefore, the solar wind is highly unlikely to be the source of the NRM in CV chondrites. Nevertheless, future high sensitivity paleomagnetic studies of rapidly-cooled meteorites with high magnetic recording fidelity could potentially trace the evolution of the solar wind field in time.
1Mehmet Yesiltas
Spectrochmica Acta Part A: Molecular and Biomolecular Spectroscopy 194, 92-101 Link to Article [https://doi.org/10.1016/j.saa.2018.01.021]
1Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli 39000, Turkey
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1A.A.Maksimova,1M.I.Oshtrakha,1A.V.Chukina,2I.Felner,1G.A.Yakovlev,1V.A.Semionkin
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 192, 275-284 Link to Article [https://doi.org/10.1016/j.saa.2017.10.056]
1Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation
2Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
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1,2Farhang Nabiei, 1James Badro, 2,5Teresa Dennenwaldt, 2Emad Oveisi, 2Marco Cantoni, 2,5Cécile Hébert, 6Ahmed El Goresy, 7Jean-Alix Barrat, 1Philippe Gillet
Nature Communications 9, 1327 Link to Article [doi:10.1038/s41467-018-03808-6]
1Earth and Planetary Science Laboratory (EPSL), Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
2Interdisciplinary Center for Electron Microscopy (CIME), Ecole 3Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
4Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Paris, France
5Electron Spectrometry and Microscopy Laboratory (LSME), Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
6Bayerisches Geoinstitut, Universität Bayreuth, Bayreuth, Germany
7Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, Plouzané, France
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Cosmochemistry Papers 