^1,2,3Konstantin D. Litasov, ¹Nikolay M. Podgornykh
Journal of Raman Spectroscopy 48, 1518-1527 Link to Article [DOI: 10.1002/jrs.5119DOI: 10.1002/jrs.5119]
¹V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
²Novosibirsk State University, Novosibirsk, Russia
³Konstantin D. Litasov, V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Koptyuga Ave., 3, Novosibirsk 630090, Russia.

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¹Punam Dalai, ¹Hannes Lukas Pleyer, ¹Henry Strasdeit, ¹Stefan Fox
Origins of Life and Biospheres 47, 427-452 Link to Article [DOI https://doi.org/10.1007/s11084-016-9523-0]
¹Department of Bioinorganic Chemistry, Institute of Chemistry University of Hohenheim Stuttgart Germany

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¹Ecaterina O. Coman, ¹Bradley L. Jolliff, ¹Paul Carpenter
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.02.008]
¹Washington University in St. Louis, Saint Louis, MO, 63123, USA
Copyright Elsevier

This paper presents results of coordinated ultraviolet and visible wavelength reflectance measurements, X-ray diffraction analyses of mineral components, and micro X-ray fluorescence analyses of Ti concentrations of 13 lunar soil samples (<210 μm) that span a range of maturity and TiO2 contents. Results of these analyses are used to determine the effects of soil maturity, TiO2 concentration, and specific mineralogical makeup, especially ilmenite content, on the ultraviolet/visible (UV/VIS) ratio for application to remote sensing observations of the Moon and other airless bodies. We find that measured ilmenite weight percent correlates highly with measured TiO2 concentrations. Thus, the ilmenite content is a good predictor of TiO2 concentration. Ilmenite is the main contributor of TiO2 for soils with greater than about 2 weight percent TiO2, so we take the effects of TiO2 on reflectance spectra to be essentially those of ilmenite. Constraining the data set to eight mature Apollo soils, we find that among the UV/VIS ratios from laboratory-measured spectra, the 321/415 nm ratio shows the best correlation with TiO2 and ilmenite. Moreover, for soils with similar maturity in the submature to mature range, those with higher TiO2 have higher 321/415 UV/VIS ratios. Finally, the correlation between TiO2 content and 321/415 ratio in samples measured in the lab appears weaker than for the same relationship using the Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) spectral data for the 321/415 ratio of Apollo ground-truth sites. The correlation between lab-derived 321/415 ratios and TiO2 content for measured samples improves when low-maturity samples are excluded from the dataset, implying that the LROC WAC spectra at 400 m/pix spatial resolution senses mostly mature soil.

¹V.A.Alekseev et al. (>10)
Bulletin of the Lebedev Physics Institute 44, 336-339 Link to Article [DOI
https://doi.org/10.3103/S1068335617110069%5D
¹Vernadsky Institute of Geochemistry and Analytical ChemistryRussian Academy of SciencesMoscowRussia

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¹O. Pravdivtseva, ²A.N. Krot, ¹C.M. Hohenberg
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.02.004]
¹Physics Department, Washington University, St. Louis MO 63130, USA
²Hawai‘i Institute of Geophysics and Planetology, School of Ocean, Earth Science and Technology, University of Hawai’i at Mānoa, Honolulu, HI 96822, USA
Copyright Elsevier

The I-Xe system was studied in a ferromagnetic sample separated from the Orgueil CI carbonaceous chondrite with a hand-held magnet and in two magnetite samples, one chemically separated before and the other one after neutron irradiation. This work was done in order to investigate the effects of chemical separation by LiCl and NaOH on the I-Xe system in magnetite. Our test demonstrated that the chemical separation of magnetite before irradiation using either LiCl or NaOH, or both, does not contaminate the sample with iodine and thus cannot lead to erroneous I-Xe ages due to introduction of uncorrelated 128∗Xe.

The I-Xe ages of two Orgueil magnetite samples are mutually consistent within experimental uncertainties and, when normalized to an absolute time scale with the reevaluated Shallowater aubrite standard, place the onset of aqueous alteration on the CI parent body at 4564.3 ± 0.3 Ma, 2.9 ± 0.3 Ma after formation of the CV Ca-AI-rich inclusions (CAIs). The I-Xe age of the ferromagnetic Orgueil separate is 3.4 Ma younger, corresponding to a closure of the I-Xe system at 4560.9 ± 0.2 Ma. These and previously published I-Xe data for Orgueil (Hohenberg et al., 2002) indicate that aqueous alteration on the CI parent body lasted for at least 5 Ma.

Although the two magnetite samples gave indistinguishable I-Xe ages, their temperature release profiles differed. One of the two Orgueil magnetites released less radiogenic Xe than the other, 80% of it corresponding to the low-temperature peak of the release profile, compared to only 6% in case of the second Orgueil magnetite sample. This could be due to the difference in iodine trapping efficiencies for magnetite grains of different morphologies. Alternatively, the magnetite grains with the lower radiogenic Xe concentrations may have formed at a later stage of alteration when iodine in an aqueous solution was depleted.

¹Larry R. Nittler, ¹Conel M.O’D. Alexander, ¹Jemma Davidson, ¹My E.I. Riebe,² Rhonda M. Stroud, ¹Jianhua Wang
Geochimica et Cosmochimcia Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.01.038https://doi.org/10.1016/j.gca.2018.01.038]
¹Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.
²Materials Science and Technology Division, Code 6366, US Naval Research Laboratory, Washington, DC 20375-5320, USA.
Copyright Elsevier

NanoSIMS C-, N-, and O-isotopic mapping of matrix in CO3.0 chondrite Dominion Range (DOM) 08006 revealed it to have in its matrix the highest abundance of presolar O-rich grains (257 +76/-96 ppm, 2σ) of any meteorite. It also has a matrix abundance of presolar SiC of 35 (+25/-17, 2 σ) ppm, similar to that seen across primitive chondrite classes. This provides additional support to bulk isotopic and petrologic evidence that DOM 08006 is the most primitive known CO meteorite. Transmission electron microscopy of five presolar silicate grains revealed one to have a composite mineralogy similar to larger amoeboid olivine aggregates and consistent with equilibrium condensation, two non-stoichiometric amorphous grains and two olivine grains, though one is identified as such solely based on its composition. We also found insoluble organic matter (IOM) to be present primarily as sub-micron inclusions with ranges of C- and N-isotopic anomalies similar to those seen in primitive CR chondrites and interplanetary dust particles. In contrast to other primitive extraterrestrial materials, H isotopic imaging showed normal and homogeneous D/H. Most likely, DOM 08006 and other CO chondrites accreted a similar complement of primitive and isotopically anomalous organic matter to that found in other chondrite classes and IDPs, but the very limited amount of thermal metamorphism experienced by DOM 08006 has caused loss of D-rich organic moieties, while not substantially affecting either the molecular carriers of C and N anomalies or most inorganic phases in the meteorite. One C-rich grain that was highly depleted in 13C and 15N was identified; we propose it originated in the Sun’s parental molecular cloud.

^1,2Janice L. Bishop, ^3,4Alberto G. Fairén, ⁵Joseph R. Michalski, ⁶Luis Gago-Duport, ⁷Leslie L. Baker, ^8,9Michael A. Velbel, ¹⁰Christoph Gross, ¹¹Elizabeth B. Rampe
Nature Astronomy (in Press) Link to Article [doi:10.1038/s41550-017-0377-9]
¹SETI Institute, Mountain View, CA, USA
²National Aeronautics and Space Administration’s Ames Research Center, Moffett Field, CA, USA
³Centro de Astrobiología (Consejo Superior de Investigaciones Científicas–Instituto Nacional de Técnica Aeroespacial), Madrid, Spain
⁴Cornell University, Ithaca, NY, USA
⁵Department of Earth Sciences & Laboratory for Space Research, University of Hong Kong, Hong Kong, China
⁶University of Vigo, Vigo, Spain
⁷University of Idaho, Moscow, ID, USA
⁸Michigan State University, East Lansing, MI, USA
⁹Smithsonian Institution, Washington, DC, USA
¹⁰Freie Universität Berlin, Berlin, Germany
¹¹National Aeronautics and Space Administration–Johnson Space Center, Houston, TX, USA

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^1,2Margaret M. McAdam, ¹Jessica M. Sunshine, ^3,4Kieren T. Howard, ⁵Conel M. Alexander, ⁶Timothy J. McCoy, ⁷Schelte J. Bus
Icarus 306, 32-49 Link to Article [https://doi.org/10.1016/j.icarus.2018.01.024]
¹University of Maryland, Department of Astronomy, College Park, MD 20740, USA
²Northern Arizona University, Department of Physics and Astronomy, Flagstaff AZ 86011, USA
³American Museum of Natural History, Central Park West & 79th St, New York, NY 10024, USA
⁴Kingsborough Community College, 2001 Oriental Blvd, Brooklyn, NY 11235, USA
⁵Department of Terrestrial Magnetism, Carnegie Institution, 1530 P St NW, Washington, DC 20005, USA
⁶National Museum of Natural History, Smithsonian Institution, 600 Maryland Avenue SW, Washington, DC 20002, USA
¹⁷University of Hawaii, Institute for Astronomy, 2444 Dole St, Honolulu, HI 96822, USA
Copyright Elsevier

Least-processed carbonaceous chondrites (carbonaceous chondrites that have experienced minimal aqueous alteration and thermal metamorphism) are characterized by their predominately amorphous iron-rich silicate interchondrule matrices and chondrule rims. This material is highly susceptible to destruction by the parent body processes of thermal metamorphism or aqueous alteration. The presence of abundant amorphous material in a meteorite indicates that the parent body, or at least a region of the parent body, experienced minimal processing since the time of accretion. The CO chemical group of carbonaceous chondrites has a significant number of these least-processed samples. We present visible/near-infrared and mid-infrared spectra of eight least-processed CO meteorites (petrologic type 3.0–3.1). In the visible/near-infrared, these COs are characterized by a broad weak feature that was first observed by Cloutis et al. (2012) to be at 1.3-µm and attributed to iron-rich amorphous silicate matrix materials. This feature is observed to be centered at 1.4-µm for terrestrially unweathered, least-processed CO meteorites. At mid-infrared wavelengths, a 21-µm feature, consistent with Si–O vibrations of amorphous materials and glasses, is also present. The spectral features of iron-rich amorphous silicate matrix are absent in both the near- and mid-infrared spectra of higher metamorphic grade COs because this material has recrystallized as crystalline olivine. Furthermore, spectra of least-processed primitive meteorites from other chemical groups (CRs, MET 00426 and QUE 99177, and C2-ungrouped Acfer 094), also exhibit a 21-µm feature. Thus, we conclude that the 1.4- and 21-µm features are characteristic of primitive least-processed meteorites from all chemical groups of carbonaceous chondrites. Finally, we present an IRTF + SPeX observation of asteroid (93) Minerva that has spectral similarities in the visible/near-infrared to the least-processed CO carbonaceous chondrites. While Minerva is not the only CO-like asteroid (e.g., Burbine et al., 2001), Minerva is likely the least-processed CO-like asteroid observed to date.

^1,2K.R. Bermingham, ²N. Gussone, ^2,3K. Mezger, ^2,4J. Krause
Geochmica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.01.034]
¹Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD-20740 USA
²Institut für Mineralogie, Westfälische Wilhelms-Universität, Corrensstraße 24, Münster, 48149 Germany
³Institut für Geologie, Universität Bern, Baltzerstrasse 1 + 3, Bern, 3012 Switzerland
⁴Helmholtz-Zentrum Dresden – Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Chemnitzer Straße 40, 09599 Freiberg, Germany
Copyright Elsevier

The Ca isotope composition of meteorites and their components may vary due to mass-dependent and/or -independent isotope effects. In order to evaluate the origin of these effects, five amoeboid olivine aggregates (AOAs), three calcium aluminum inclusions (CAIs), five chondrules (C), a dark inclusion from Allende (CV3), two dark inclusions from North West Africa 753 (NWA 753; R3.9), and a whole rock sample of Orgueil (CI1) were analyzed. This is the first coupled mass-dependent and -independent Ca isotope dataset to include AOAs and dark inclusions. Where sample masses permit, Ca isotope data are reported with corresponding petrographic analyses and rare earth element (REE) relative abundance patterns. The CAIs and AOAs are enriched in light Ca isotopes (δ44/40Ca -5.32 to +0.72, where δ44/40Ca is reported relative to SRM 915a). Samples CAI 5 and AOA 1 have anomalous Group II REE patterns. These REE and δ44/40Ca data suggest that the CAI 5 and AOA 1 compositions were set via kinetic isotope fractionation during condensation and evaporation. The remaining samples show mass-dependent Ca isotope variations which cluster between δ44/40Ca +0.53 and +1.59, some of which are coupled with unfractionated REE abundance patterns. These meteoritic components likely formed through the coaccretion of the evaporative residue and condensate following Group II CAI formation or their chemical and isotopic signatures were decoupled (e.g., via nebular or parent-body alteration). The whole rock sample of Orgueil has a δ44/40Ca +0.67 ±0.18 which is in agreement with most published data. Parent-body alteration, terrestrial alteration, and variable sampling of Ca-rich meteoritic components can have an effect on δ44/40Ca compositions in whole rock meteorites.

Samples AOA 1, CAI 5, C 2, and C 4 display mass-independent 48/44Ca anomalies (ε48/44Ca +6 to +12) which are resolved from the standard composition. Other samples measured for these effects (AOA 5, CAI 1, CAI 2, C 3, D 1, D 2, D 3) possess the same 48/44Ca isotope composition as the standard within analytical uncertainty. These data indicate a heterogeneous distribution of 48Ca in the early solar nebula during formation of CAIs, AOAs, and chondrules. In a δ44/40Ca vs. ε48/44Ca plot, no strong correlation is evident which suggests that the thermal processing event which caused a heterogeneous distribution of ε48/44Ca in the solar nebula is unlikely to be directly related to the thermal processing event that caused coupled REE and Ca mass-dependent isotopic fractionation in meteoritic components.

¹Aaron J. Cavosie, ¹Nicholas E. Timms, ²Timmons M. Erickson, ^3,4Christian Koeberl
Geology (in Press) Link to Article [DOI: https://doi.org/10.1130/G39711.1]
¹The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, Perth, WA 6102, Australia
²Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas 77058, USA
³Natural History Museum, 1010 Vienna, Austria
⁴Department of Lithospheric Research, University of Vienna, 1090 Vienna, Austria

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