¹A.A.Maksimova, ¹M.I.Oshtrakh, ¹A.V.Chukin, ²I.Felner, ¹G.A.Yakovlev, ¹V.A.Semionkin
Spectrochmica 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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^1,2W. Neumann,^1,3T. S. Kruijer,²D. Breuer,¹T. Kleine
Journal of Geophysical Research, Planets Link to Article [DOI: 10.1002/2017JE005411]
¹Institut für Planetologie, Westfälische Wilhelms-Universität (WWU), Münster, Deutschland
²Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Deutschland
³Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California, USA
Published by arrangement with John Wiley & Sons

Iron meteorites provide some of the most direct insights into the processes and timescales of core formation in planetesimals. Of these, group IVB irons stand out by having one of the youngest 182Hf-182W model ages for metal segregation (2.9 ± 0.6 Ma after solar system formation), as well as the lowest bulk sulphur content and hence highest liquidus temperature. Here, using a new model for the internal evolution of the IVB parent body, we show that a single stage of metal-silicate separation cannot account for the complete melting of pure Fe metal at the relatively late time given by the Hf-W model age. Instead, a complex metal-silicate separation scenario is required that includes migration of partial silicate melts, formation of a shallow magma ocean and core formation in two distinct stages of metal segregation. In the first stage, a proto-core formed at ≈1.5 Ma via settling of metal particles in a mantle magma ocean, followed by metal segregation from a shallow magma ocean at ≈5.4 Ma. As these stages of metal segregation occurred at different times, the two metal fractions had different 182W compositions. Consequently, the final 182W composition of the IVB core does not correspond to a single differentiation event, but represents the average composition of early- and late-segregated core fractions. Our best-fit model indicates a ≈100 km radius for the IVB parent body and provides an accretion age of ≈0.1 − 0.5 Ma after solar system formation. The computed solidification time is, furthermore, consistent with the Re-Os age for crystallization of the IVB core.

^1,2O.Ruesch et al (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.01.022]
¹NASA Goddard Space Flight Center/USRA, Greenbelt, MD 20771, USA
²ESTEC, European Space Agency, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
Copyright Elsevier

Vinalia and Cerealia Faculae are bright and salt-rich localized areas in Occator crater on Ceres. The predominance of the near-infrared signature of sodium carbonate on these surfaces suggests their original material was a brine. Here we analyze Dawn Framing Camera’s images and characterize the surfaces as composed of a central structure, either a possible depression (Vinalia) or a central dome (Cerealia), and a discontinuous mantling. We consider three materials enabling the ascent and formation of the faculae: ice ascent with sublimation and carbonate particle lofting, pure gas emission entraining carbonate particles, and brine extrusion. We find that a mechanism explaining the entire range of morphologies, topographies, as well as the common composition of the deposits is brine fountaining. This process consists of briny liquid extrusion, followed by flash freezing of carbonate and ice particles, particle fallback, and sublimation. Subsequent increase in briny liquid viscosity leads to doming. Dawn observations did not detect currently active water plumes, indicating the frequency of such extrusions is longer than years.

¹J.T. Poitras, ¹E.A. Cloutis, ², M.R. Salvatore, ³S.A. Mertzman, ¹D.M. Applin, ¹P. Mann
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.01.023]
¹Department of Geography, University of Winnipeg, Winnipeg MB R3B 2E9 Canada
²Department of Physics & Astronomy, Northern Arizona University, Flagstaff, Arizona, USA 86011
³Department of Earth and Environment, Franklin and Marshall College, Lancaster, Pennsylvania, USA
Copyright Elsevier

We investigated the spectral reflectance properties of minerals under a simulated Martian environment. Twenty-Eight different hydrated or hydroxylated phases of carbonates, sulfates, and silica minerals were selected based on past detection on Mars through spectral remote sensing data. Samples were ground and dry sieved to <45 µm grain size and characterized by XRD before and after 133 days inside a simulated Martian surface environment (pressure 5 torr and CO2 fed). Reflectance spectra from 0.35 to 4 µm were taken periodically through a sapphire (0.35 to 2.5 µm) and zinc selenide (2.5 to 4 µm) window Over a 133-day period. Mineral stability on the Martian surface was assessed through changes in spectral characteristics. Results indicate that the hydrated carbonates studied would be stable on the surface of Mars, only losing adsorbed H2O while maintaining their diagnostic spectral features. Sulfates were less stable, often with shifts in the band position of the SO, Fe, and OH absorption features. Silicas displayed spectral shifts related to SiOH and hydration state of the mineral surface, while diagnostic bands for quartz were stable. Previous detection of carbonate minerals based on 2.3-2.5 µm and 3.4-3.9 µm features appear to be consistent with our results. Sulfate mineral detection is more questionable since there can be shifts in band position related to SO4. The loss of the 0.43 µm Fe3+ band in many of the sulfates indicate that there are fewer potential candidates for Fe3+ sulfates to permanently exist on the Martian surface based on this band. The gypsum sample changed phase to basanite during desiccation as demonstrated by both reflectance and XRD.Silica on Mars has been detected using band depth ratio at 1.91 and 1.96 µm and band minimum position of the 1.4 µm feature, and the properties are also used to determine their age. This technique continues to be useful for positive silica identifications, however, silica age appears to be less consistent with our laboratory data. These results will be useful in spectral libraries for characterizing Martian remote sensed data.

^1,2,3Gunther Kletetschka
Earth and Planetary Science Letters 487, 1-8 Link to Article [https://doi.org/10.1016/j.epsl.2018.01.020]
¹Institute of Geology, Academy of Sciences of the Czech Republic, Czech Republic
²Faculty of Science, Charles University, Czech Republic
³Department of Geology and Geophysics, University of Alaska Fairbanks, USA
Copyright Elsevier

The origin of magnetization in Allende may have significant implications for our understanding of core formation/differentiation/dynamo processes in chondrite parent bodies. The magnetic Allende data may contain information that could constrain the magnetic history of Allende. The measurements on Allende chondrules reveal an existence of magnetization component that was likely acquired during the meteorite transit to terrestrial conditions. Both the pyrrhotite carrying magnetic remanence intensity and direction of the chondrules change erratically when subjecting the Allende meteorite’s chondrules to temperatures near 77 K and back to room temperature. Chondrules with more intense original magnetization are denser and contain larger inverse thermoremanent magnetization (ITRM). Temperature dependent monitoring of ITRM revealed that magnetization was acquired at temperature near 270 K. Such temperature is consistent with the condition when, in addition to temperature increase, the atmospheric uniaxial pressure applied during the meteorite entry on the porous material was responsible for meteorite break up in the atmosphere. During this process, collapse of the pore space in the matrix and some chondrules would generate crystalline anisotropy energy accumulation within pyrrhotite grains in form of parasitic magnetic transition.

¹Maurizio Gemelli,¹Tommaso Di Rocco,¹Luigi Folco,¹Massimo D’Orazio
Geostandards and Geoanalytical Research 41, 613-632 Link to Article [DOI: 10.1111/ggr.12179]
¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy

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¹Tomoaki Kubo, ²Mari Kono, ^1,2Masahiro Imamur, ¹Takumi Kato, ¹Seiichiro Uehara, ³Tadashi Kondo, ⁴Yuji Higo, ⁴Yoshinori Tange, ⁵Takumi Kikegawa
Physics of the Earth and Planetary Interiors 272, 50-57 Link to Article [https://doi.org/10.1016/j.pepi.2017.09.006]
¹Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan
²Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University, Fukuoka 819-0395, Japan
³Department of Earth Space Science, Osaka University, Osaka 560-0043, Japan
⁴Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan
⁵Photon Factory, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan

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^1,2Albert Jambon
Journal of Archaeological Science 88, 47-53 Link to Article [https://doi.org/10.1016/j.jas.2017.09.008]
¹Université Côte D’Azur, UPMC, CNRS, OCA, IRD, Géoazur, Sophia Antipolis, France
²Sorbonne Universités, UPMC Univ Paris 06, MNHN and IMPMC, France

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¹Patrick H. Donohue, ¹Clive R. Neal
American Mineralogist 103, 284-297 Link to Article [DOI: https://doi.org/10.2138/am-2018-6173]
¹Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, U.S.A.
Copyright: The Mineralogical Society of America

Basalt fragment 71597 is the sole high-titanium mare basalt showing evidence for olivine accumulation during formation. The petrogenesis of this unique sample was investigated using quantitative textural analysis and major- and trace-element mineral geochemistry. Crystal size distribution analysis identified two size populations of olivine, which we separate into cumulate and matrix olivine. The spatial distribution of olivine also supports clustering of olivine crystals, likely during accumulation. Observed mineral chemistry was consistent with an origin through olivine accumulation, although where this occurred cannot be discerned (e.g., in ponded melts at the base of or in the lunar crust, or within a thick high-Ti basalt flow). Attempts to place 71597 within a geochemical group were inconclusive both using subtraction of cumulate olivine from bulk composition, and by modal recombination of major phases. However, equilibrium liquid compositions of augite and plagioclase are determined to be consistent with an origin by fractionation from the Type B2 chemical suite of Apollo 17 high-Ti basalts. This method of classification has potential for placing other Type U (“Unclassified”) basalts into chemical suites.

^1,2Fan Wang, ³Brenda B. Bowen, ⁴Ji-Hye Seo, ^2,4Greg Michalski
American Mineralogist 103, 197-206 Link to Article [DOI: https://doi.org/10.2138/am-2018-6141]
¹School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen, Guangdong 518055, China
²Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, U.S.A.
³Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, U.S.A.
⁴Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, U.S.A.
Copyright: The Mineralogical Society of America

Large amounts of nitrate salts occur in very specific environments and somewhat rare hyper-arid conditions, which may provide clues to fundamentally different nitrogen cycling and life survival mechanisms. Remote detection of ancient and modern nitrates on Earth and on other planetary bodies where they may occur requires a detailed understanding of their visible to near infrared (VNIR) spectral signatures. This study explores the VNIR spectral characteristics of several synthetic nitrate salts, sulfate minerals, and nitrate-bearing field samples from the Atacama Desert, Chile, to identify diagnostic spectral features of nitrate and possible interferences from other coexisting minerals. Results indicated that most of the nitrate salts have characteristic absorptions around 1.81, 1.94, 2.06, 2.21, and 2.42 μm. A significant positive correlation exists between the continuum-removed band depths of the 2.42 μm absorption and nitrate contents for the Atacama regolith samples, especially for samples with >10 wt% nitrate. The five absorption features of nitrate in the field spectra collected from multiple nitrate-rich regions in the Atacama Desert were then evaluated to determine the variabilities in these features in natural settings, while the band depths of 2.42 μm absorption were further calculated on the continuum-removed field spectra to estimate the nitrate abundances at the study sites. This work will supplement spectral libraries where nitrate spectra are lacking and have implications for future comparisons to planetary spectra to search for potentially life-related nitrate on Mars.