Author: Administrator

Spectral behavior of sulfides in simulated daytime surface conditions of Mercury: Supporting past (MESSENGER) and future missions (BepiColombo)

Posted by

0

1I.Varatharajan,1A.Maturilli,1J.Helbert,2G.Alemanno,3H.Hiesinger
Earth and Planetary Science Letters (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2019.05.020]
1Deutsches Zentrum für Luft- Und Raumfahrt
2Universita del Salento
3Westfälische Wilhelms-Universität Münster
Copyright Elsevier

To detect the mineral diversity of a planet’s surface, it is essential to study the spectral variations over a broad wavelength range at relevant simulated laboratory conditions. The MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) mission to Mercury discovered that irrespective of its formation closest to the Sun, Mercury is richer in volatiles than previously expected. This is especially true for sulfur (S), with an average abundance of 4 wt%. It has been proposed that sulfur in the interior of Mercury can be brought to the surface through volcanic activity in the form of sulfides as slag deposits in Mercury hollows and pyroclastic deposits. However, comprehensive spectral library of sulfide minerals measured under vacuum conditions in a wide spectral range (0.2–100 μm) was lacking. This affects the detectability and understanding of the distribution, abundance, and type of sulfides on Mercury using remote-sensing spectral observations. In the case of Mercury, the effect of thermal weathering affecting the spectral behavior of these sulfides must be studied carefully for their effective detection. In this study, we present a spectral library of synthetic sulfides including MgS, FeS, CaS, CrS, TiS, NaS, and MnS. For each sample, we performed emissivity measurements in the thermal infrared range (TIR: ∼7–14 μm) for sample temperatures from 100 °C–500 °C, covering the daytime temperature cycle on Mercury’s surface. In addition, for each sample we measured the spectral reflectance of fresh and thermally processed sulfides over a wide spectral range (0.2–100 μm) and at four different phase angles, 26°, 40°, 60°, 80°. This spectral library facilitates the detection of sulfides by past and future missions to Mercury by any optical spectrometer of any spectral range. Specifically, the emissivity measurements in this study will support the Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS) instrument on the ESA/JAXA BepiColombo mission, which will study the surface mineralogy over a wavelength range of 7–14 μm at a spatial resolution of 500 m/pixel. The measured reflectance of these sulfides in 0.2–100 μm at various phase angles will support the interpretation of measurements from past (MDIS, MASCS on MESSENGER) and future missions (SIMBIO-SYS on BepiColombo).

A Methodological Approach to the Analysis of Rocks and Meteorites by Inductively Coupled Plasma Atomic Emission Spectrometry

Posted by

0

1Sedykh, E.M.,1Gromyak, I.N.,1Lorents, K.A.,1Skripnik, A.Y.,1Kolotov, V.P.
Journal of Analytical Chemistry 74, 393-400 Link to Article [DOI: 10.1134/S1061934819040129]
1Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991, Russian Federation

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

Comparison of the 57 Fe hyperfine interactions in silicate phases in Sariçiçek howardite and some ordinary chondrites

Posted by

0

1Maksimova, A.A.,2Unsalan, O.,1Chukin, A.V.,1Oshtrakh, M.I.
Hyperfine Interactions 240, 47 Link to Article [DOI: 10.1007/s10751-019-1593-8]
1Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
2Department of Physics, Faculty of Science, Ege University, Izmir, Bornova 35100, Turkey

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

Implications of K, Cu and Zn isotopes for the formation of tektites

Posted by

0

1,2,3Yun Jiang,3Heng Chen,3Bruce Fegley Jr.,3Katharina Lodders,4Weibiao Hsu,5Stein B.Jacobsen,3,5KunWang(王昆)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.06.003]
1CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
2CAS Center for Excellence in Comparative Planetology, China
3Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
4Space Science Institute, Macau University of Science and Technology, Macau
5Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA
Copyright Elsevier

Tektites are mm to cm sized glassy objects generated through high-energy meteoroid impacts on the surface of the Earth under high temperature and pressure, and reducing conditions. They are the products of large-scale catastrophic events in Earth’s history and can be used to understand the behavior of moderately volatile elements (e.g., K and Zn) during impact vaporization events. Here, we report bulk K isotopic compositions of tektites from three different strewn fields and “in-situ” profile analysis of both K and Zn isotopes in one complete tektite. All tektites span a narrow range in their K isotopic compositions (δ41KBSE: −0.10 ± 0.03‰ to 0.16 ± 0.04‰), revealing no discernible K isotopic fractionation from the Bulk Silicate Earth (BSE) and upper continental crust materials, which is consistent with previous results. In contrast, Zn isotopes show a large variation (δ66Zn: −0.39 ± 0.02‰ to 2.38 ± 0.03‰) even within one specimen. In order to provide a coherent explanation for the different behavior of moderately volatile elements (K, Zn and Cu), we have conducted thermochemical calculations to compute the partial vapor pressures of Cu2O, K2O, and ZnO dissolved in silicate melts as a function of temperature, pressure, oxygen and chlorine fugacities. In a large range of the parameter space, the calculations show that Cu and Zn can be vaporized much easier than K and thus produce large isotopic fractionation. In contrast, the lithophile element K is more prone to remain in the silicate melt because of its very low activity coefficient in the melt, and thus the K isotopes remain unfractionated. This study provides new constraints on the formation of tektites and is consistent with a “bubble-stripping” model to explain the extreme water and volatiles depletion in tektites.

Effects of pH2O, pH2 and fO2 on the diffusion of h-bearing species in lunar basaltic liquid and an iron-free basaltic analog at 1 atm

Posted by

0

1,2,3M.E.Newcombe, 1J.R.Beckett,1M.B.Baker, 4S.Newman,1Y.Guan,1J.M.Eiler1E.M.Stolper
Geochmica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.05.033]
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
2Lamont Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, USA
3Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015
4Bay Area Air Quality District, 375 Beale St., Suite 600, San Francisco, CA 94105
Copyright Elsevier

We have experimentally determined the diffusivity of water in a representative lunar basaltic liquid composition (LG) and in an iron-free analog of a basaltic liquid (AD) at the low water concentrations and low oxygen fugacities (fO2) relevant to the eruption of lunar basalts. Experiments were conducted at 1 atm and 1350 °C over a range of pH2/pH2O from near zero to ∼10 and a range in fO2 spanning ∼9 orders of magnitude (from 2.2 log units below the iron-wüstite buffer, IW–2.2, to IW+6.7). The water concentrations measured in our quenched experimental glasses by secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (FTIR) vary from a few ppm to ∼430 ppm. Water concentration gradients in the majority of our AD experiments are well described by models in which the diffusivity of water (Dwater∗ ) has a constant value of ∼2×10–10 m2/s, while our LG results indicate that Dwater∗ in LG melt has a constant value of ∼6×10–10 m2/s under the conditions of our experiments. Water concentration gradients in hydration and dehydration experiments that were run simultaneously in H2/CO2 gas mixtures are well described by the same Dwater∗ , and water concentrations measured near the melt-vapor interfaces of these experiment pairs are approximately the same. These observations strongly support an equilibrium boundary condition for our experiments containing >70 ppm H2O. However, dehydration experiments into nominally anhydrous CO2, N2, and CO/CO2 gas mixtures leave some scope for the importance of kinetics during dehydration of melts containing less than a few 10’s of ppm H2O. Comparison of our results with the modified speciation model (Ni et al., 2013) in which both molecular water and hydroxyl are allowed to diffuse suggests that we have resolved the diffusivity of hydroxyl (DOH ) in AD and LG melts. Our results support a positive correlation between DOH and melt depolymerization. Best-fit values of Dwater∗ for our LG experiments vary within a factor of ∼2 over a range of pH2/pH2O from 0.007 to 9.7 and a range of logfO2 from IW–2.2 to IW+4.9. The relative insensitivity of our best-fit values of Dwater∗ to variations in pH2 suggests that H2 diffusion did not control the rate of degassing of H-bearing species from the lunar glasses of Saal et al. (2008); however, we cannot rule out a role for molecular H2 diffusion under lower-temperature and/or higher-pressure conditions than explored in our experiments. The value of Dwater∗ chosen by Saal et al. (2008) for modeling the diffusive degassing of the lunar volcanic glasses is within a factor of ∼2 of our measured value in LG melt at 1350 °C. By coupling our LG results at 1350 °C with an activation energy of 220 kJ/mol (Zhang et al. 2017), we obtain the following Arrhenius relationship, which can be used to model syneruptive diffusive water loss from lunar melt beads:

Dwater∗(m2/s)=7.2×10-3exp-2.6×104T(K) .

Indigenous Organic-Oxidized Fluid Interactions in the Tissint Mars Meteorite

Posted by

0

1,2Jaramillo, E.A.,3Royle, S.H.,4,5Claire, M.W.,1,3Kounaves, S.P.,3Sephton, M.A.
Geophysical Research Letters 46, 3090-3098 Link to Article [DOI: 10.1029/2018GL081335]
1Department of Chemistry, Tufts University, Medford, MA, United States
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
3Department of Earth Science and Engineering, Imperial College London, London, United Kingdom
4School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St. Andrews, Saint Andrews, United Kingdom
5Blue Marble Space Institute of Science, Seattle, WA, United States

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

An extremely heavy chlorine reservoir in the Moon: Insights from the apatite in lunar meteorites

Posted by

0

1,2,3Wang, Y.,2,3Hsu, W.,4Guan, Y.
Scientific Reports 9, 5727 Link to Article [DOI: 10.1038/s41598-019-42224-8]
1Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210034, China
2The State Key Laboratory of Lunar and Planetary Science/Space Science Institute, Macau University of Science and Technology, Taipa, China
3CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Nanjing, 210034, China
4Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States

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

Application of instrumental methods in the Morasko Meteorite investigations [Zastosowanie metod instrumentalnych w badaniach meteorytu Morasko]

Posted by

0

1Duczmal-Czernikiewicz, A.,1Muszynski, A.,2Runka, T.,3Golebiewska, B.,1Michalska, D.,
4Karwowski, L.
Przeglad Geologiczny 67, 156-158 Link to Article [DOI: 10.7306/2019.6]
1Instytut Geologii, Uniwersytet Im. Adama Mickiewicza W Poznaniu, ul.Bogumila Krygowskiego 12, Poznan, 61-680, Poland
2Instytut Badan Matcrialowych I Inzynierii Kwantowcj, Politechnika Poznanska, ul. Piotrowo 2, Poznan, 61-138, Poland
3AGH Akademia Gorniczo-Hutnicza, Katedra Mineralogii, Geochemii Petrografii i Geochemii, al. Mickiewicza 30, Krakow, 30-059, Poland
4Uniwersytet and Slaski, Katedra Geochemii, Mineralogii i Petrografii, ul. Bqdzinska 60, Sosnowiec, 41-205, Poland

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

Titanium local coordination environments in Cretaceous–Paleogene and Devonian–Carboniferous boundary sediments as a possible marker for large meteorite impact

Posted by

0

1,2,3Tobase, T.,1Yoshiasa, A.,1Komatsu, T.,1Maekawa, T.,1Hongu, H.,4Okube, M.,4Arima, H.,4Sugiyama, K.
Physics and Chemistry of Minerals (in Press) Link to Article [DOI: 10.1007/s00269-019-01030-4]
1Graduate School of Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan
2Université de Lorraine, CRM2, UMR 7036, Vandoeuvre-les-Nancy, 54506, France
3CNRS, CRM2, UMR 7036, Vandoeuvre-les-Nancy, 54506, France
4Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan

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

Multiple Outbursts of Asteroid (6478) Gault*

Posted by

0

Quanzhi Ye (叶泉志)1,2 et al. (>10)
Astrophysical Journal Letters 874, L16 Link to Article [DOI: 10.3847/2041-8213/ab0f3c]
1Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
2Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA

Main-belt asteroid (6478) Gault unexpectedly sprouted two tails in late 2018 and early 2019, identifying it as a new active asteroid. Here we present observations obtained by the 1.2 m Zwicky Transient Facility survey telescope that provide detailed time-series coverage of the onset and evolution of Gault’s activity. Gault exhibited two brightening events, with the first one starting on 2018 October 18 ± 5 days and a second one starting on 2018 December 24 ± 1 days. The amounts of mass released are 2 × 107 kg and 1 × 106 kg, respectively. Based on photometric measurements, each event persisted for about a month. Gault’s color has not changed appreciably over time, with a pre-outburst color of g PS1 − r PS1 = 0.50 ± 0.04 and g PS1 − r PS1 = 0.46 ± 0.04 during the two outbursts. Simulations of dust dynamics shows that the ejecta consists of dust grains of up to 10 μm in size that are ejected at low velocities below $1\,{\rm{m}}\,{{\rm{s}}}^{-1}$ regardless of particle sizes. This is consistent with non-sublimation-driven ejection events. The size distribution of the dust exhibits a broken power law, with particles at 10–20 μm following a power law of −2.5 to −3.0, while larger particles follow a steeper slope of −4.0. The derived properties can be explained by either rotational excitation of the nucleus or a merger of a near-contact binary, with the latter scenario to be statistically more likely.