¹Yves Marrocchi, ¹David V. Bekaert, ¹Laurette Piani
Earth and Planetary Science Letetrs 482, 23-32 Link to Article [https://doi.org/10.1016/j.epsl.2017.10.060]
¹CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre-les-Nancy, F-54501, France
Copyright Elsevier

The origin and abundance of water accreted by carbonaceous asteroids remains underconstrained, but would provide important information on the dynamic of the protoplanetary disk. Here we report the in situ oxygen isotopic compositions of aqueously formed fayalite grains in the Kaba and Mokoia CV chondrites. CV chondrite bulk, matrix and fayalite O-isotopic compositions define the mass-independent continuous trend (δ17O = 0.84 ± 0.03 × δ18O − 4.25 ± 0.1), which shows that the main process controlling the O-isotopic composition of the CV chondrite parent body is related to isotopic exchange between 16O-rich anhydrous silicates and 17O- and 18O-rich fluid. Similar isotopic behaviors observed in CM, CR and CO chondrites demonstrate the ubiquitous nature of O-isotopic exchange as the main physical process in establishing the O-isotopic features of carbonaceous chondrites, regardless of their alteration degree. Based on these results, we developed a new approach to estimate the abundance of water accreted by carbonaceous chondrites (quantified by the water/rock ratio) with CM (0.3–0.4) ≥ CR (0.1–0.4) ≥ CV (0.1–0.2) > CO (0.01–0.10). The low water/rock ratios and the O-isotopic characteristics of secondary minerals in carbonaceous chondrites indicate they (i) formed in the main asteroid belt and (ii) accreted a locally derived (inner Solar System) water formed near the snowline by condensation from the gas phase. Such results imply low influx of D- and 17O- and 18O-rich water ice grains from the outer part of the Solar System. The latter is likely due to the presence of a Jupiter-induced gap in the protoplanetary disk that limited the inward drift of outer Solar System material at the exception of particles with size lower than 150 μm such as presolar grains. Among carbonaceous chondrites, CV chondrites show O-isotopic features suggesting potential contribution of 17–18O-rich water that may be related to their older accretion relative to other hydrated carbonaceous chondrites.

^1,2,3B.L.de Vries,⁴H.Skogby, ^5,6L.B.F.M.Waters, ^5,6M.Min
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.10.029]
¹Stockholm University Astrobiology Centre, Stockholm SE-106 91, Sweden
²AlbaNova University Centre, Stockholm University, Department of Astronomy, Stockholm SE-106 91, Sweden
³Scientific Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, Noordwijk 2201 AZ, The Netherlands
⁴Department of Geosciences, Swedish Museum of Natural History, Box 50007, Stockholm SE-104 05, Sweden
⁵SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁶Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
Copyright Elsevier

Meteorites contain minerals from Solar System asteroids with different properties (like size, presence of water, core formation). We provide new mid-IR transmission spectra of powdered meteorites to obtain templates of how mid-IR spectra of asteroidal debris would look like. This is essential for interpreting mid-IR spectra of past and future space observatories, like the James Webb Space Telescope. First we present new transmission spectra of powdered ordinary chondrite, pallasite and HED meteorites and then we combine them with already available transmission spectra of chondrites in the literature, giving a total set of 64 transmission spectra. In detail we study the spectral features of minerals in these spectra to obtain measurables used to spectroscopically distinguish between meteorite groups. Being able to differentiate between dust from different meteorite types means we can probe properties of parent bodies, like their size, if they were wet or dry and if they are differentiated (core formation) or not.

We show that the transmission spectra of wet and dry chondrites, carbonaceous and ordinary chondrites and achondrite and chondrite meteorites are distinctly different in a way one can distinguish in astronomical mid-IR spectra. Carbonaceous chondrites type < 3 (aqueously altered) show distinct features of hydrated silicates (hydrosilicates) compared to the olivine and pyroxene rich ordinary chondrites (dry and equilibrated meteorites). Also the iron concentration of the olivine in carbonaceous chondrites differs from ordinary chondrites, which can be probed by the wavelength peak position of the olivine spectral features. The transmission spectra of chondrites (not differentiated) are also strongly different from the achondrite HED meteorites (meteorites from differentiated bodies like 4 Vesta), where the latter show much stronger pyroxene signatures.

The two observables that spectroscopically separate the different meteorites groups (and thus the different types of parent bodies) are the pyroxene-olivine feature strength ratio and the peak shift of the olivine spectral features due to an increase in the iron concentration of the olivine.

^1,2Sarah R. Black, ^1,2Brian M.Hynek
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.10.032]
¹Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, 1234 Innovation Drive, Boulder, CO 80303, United States
²Department of Geological Sciences, University of Colorado Boulder, Campus Box 600 UCB, Boulder, CO 80303, United States
Copyright Elsevier

Interpretation of Martian geology relies heavily on our understanding of terrestrial analog deposits and our ability to obtain comprehensive and accurate mineralogical compositions. Many previous studies of terrestrial hydrothermal deposits relied on limited datasets and/or did not use instruments analogous to those deployed on Mars. We analyzed 100 hydrothermally altered basalts from Costa Rica, Nicaragua, and Iceland with Mars analog Visible to Short Wave Infrared (VSWIR) spectroscopy, X-ray Diffraction (XRD), and Raman laser spectrometry. Alteration mineralogy consisted of amorphous and crystalline SiO2 (cristobalite, tridymite, quartz), Ca/Al/Fe/Mg-sulfates (gypsum, anhydrite, alunite, jarosite, hexahydrite, alunogen), Fe-, Ti-, and Mg-oxides/hydroxides (hematite, goethite, anatase/brookite, brucite), elemental sulfur, and phyllosilicates (montmorillonite, kaolinite). Results indicate VSWIR is best suited for identification of X-ray amorphous materials such as hydrated SiO2 and phyllosilicates, while XRD is best utilized for highly ordered crystalline materials such as sulfates, crystalline SiO2 polymorphs, elemental sulfur, and Mg-hydroxides identification. Surprisingly, XRD had the lowest identification rates for Fe-oxides/hydroxides (42% compared to 61% and 75% for VNIR and Raman, respectively), and nearly equal identification rates as VSWIR for kaolinite (76% for VSWIR, 71% for XRD). Identification of phyllosilicates in XRD, while possible, is not as effective as VSWIR without extensive sample preparation. Our observed identification rates may be attributed to the relative abundance of materials—Fe-oxides/hydroxides being present as surface coatings, the presence of large amounts of kaolinite in some samples, and an increased particle size for kaolinite relative to other clays. Elemental sulfur and Fe- and Ti-oxides/hydroxides were more readily identified with Raman. With NASA’s current focus on habitability, hydrothermally altered areas—which we know to host a wide range of microbial life here on Earth—are of high interest and it is likely that future rovers will encounter similar mineral assemblages. Therefore, future rovers would benefit from using a combination of these methods and expanding the VSWIR sampling range to the full 300–2500 nm to conduct a comprehensive mineralogical investigation.

¹A.Raponi et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.10.023]
¹INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, I-00133 Rome, Italy
Copyright Elsevier

Ceres has been explored by NASA/Dawn spacecraft, which allowed for the discovery of the main mineralogical and compositional characteristics of Ceres’ surface. Here, we use mainly data from the Visible and InfraRed imaging spectrometer (VIR) in order to investigate the main spectral characteristics of the quadrangle Ac-H-2 Coniraya, one of the 15 quads in which Ceres’ surface has been divided. Coniraya quadrangle is characterized by the presence of mostly highly degraded impact craters of diameters between 50 and 200 km and clusters of small to midsize impact craters. Although the composition over the quadrangle appears to be quite uniform, significant differences have been detected between different craters by spectral parameters analysis and spectral modeling. Ernutet crater presents two regions with very peculiar band at 3.4 µm, typical of organics aliphatic material. One region result to be correlated with larger amount of carbonates, the other region does not present such correlation. Ikapati crater shows strong absorption bands at 4.0 µm, indicating the presence of Na-carbonates in the floor and ejecta. Ikapati, Gaue and other craters present smaller spectral features of NH4 and/or OH stretching, suggesting a volatile depletion process induced by the heating of the impact event.

¹Megha Bhatt, ²Christian Wöhler, ³Deepak Dhingra, ⁴Guneshwar Thangjam, ²Daniela Rommel, ⁴Urs Mall, ⁵Anil Bhardwaj, ²Arne Grumpe
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.10.009]
¹Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, Kerala, India
²Image Analysis Group, Dortmund University of Technology, Otto-Hahn Str. 4, Dortmund 44227, Germany
³Department of Physics, University of Idaho, 875 Perimeter Dr MS 0903, Moscow, ID 83843, USA
⁴Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, Göttingen 37077, Germany
⁵Physical Research Laboratory, Ahmedabad 380009, Gujarat, India
Copyright Elsevier

Moscoviense is one of the prominent mare-filled basin on the lunar far side holding key insights about volcanic activity on the far side. Here, we present spectral and elemental maps of mare Moscoviense, using the Moon Mineralogy Mapper (M3) and Infrared Spectrometer-2 (SIR-2) data-sets. The different mare units are mapped based on their spectral properties analyzing both quantitatively (band center, band depth) and qualitatively (Integrated Band Depth composite images), and also using their elemental compositions. We find a total of five distinct spectral units from the basin floor based on the spectral properties. Our analysis suggests that the northern part which was mapped as Iltm unit (Imbrian low Ti, low Fe) by earlier researchers is actually a distinct unit, which is different in composition and age, named as Ivltm unit (Imbrian very low Ti and very low Fe). We obtain the absolute model age of 3.2 Ga with uncertainties of +0.2/−0.5 Ga for the unit Ivltm. The newly identified basalt unit Ivltm is compositionally intermediate to the units Im and Iltm in FeO and TiO2 abundances. We find a total of five distinct spectral units from the basin floor based on the spectral properties. The units Im (Imbrian very low Ti) from southern and northern regions of the basin floor are spectrally distinct in terms of band center position and corresponding band depths but considered a single unit based on the elemental abundance analysis. The units Ivltm and Im are consistent with a high-Al basalt composition. Our detailed analysis of the entire Moscoviense basin indicates that the concentrations of orthopyroxene, olivine, and Mg-rich spinel, named as OOS rock family are widespread and dominant at the western and southern side of the middle ring of the basin with one isolated area found on the northern side of the peak ring.

¹B.Rosseau et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.10.015]
¹LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
Copyright Elsevier

Laboratory spectral measurements of relevant analogue materials were performed in the framework of the Rosetta mission in order to explain the surface spectral properties of comet 67P. Fine powders of coal, iron sulphides, silicates and their mixtures were prepared and their spectra measured in the Vis-IR range. These spectra are compared to a reference spectrum of 67P nucleus obtained with the VIRTIS/Rosetta instrument up to 2.7 µm, excluding the organics band centred at 3.2 µm. The species used are known to be chemical analogues for cometary materials which could be present at the surface of 67P. Grain sizes of the powders range from tens of nanometres to hundreds of micrometres. Some of the mixtures studied here actually reach the very low reflectance level observed by VIRTIS on 67P. The best match is provided by a mixture of sub-micron coal, pyrrhotite, and silicates. Grain sizes are in agreement with the sizes of the dust particles detected by the GIADA, MIDAS and COSIMA instruments on board Rosetta. The coal used in the experiment is responsible for the spectral slope in the visible and infrared ranges. Pyrrhotite, which is strongly absorbing, is responsible for the low albedo observed in the NIR. The darkest components dominate the spectra, especially within intimate mixtures. Depending on sample preparation, pyrrhotite can coat the coal and silicate aggregates. Such coating effects can affect the spectra as much as particle size. In contrast, silicates seem to play a minor role.

¹L.J. Hallis,^1,2L. Kemppinen,¹M. R. Lee,³L. A. Taylor
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12987]
¹School of Geographical and Earth Science, University of Glasgow, Glasgow, Scotland, UK
²School of Geographical and Earth Science, University of Glasgow, Glasgow, Scotland, UK
³School of Earth Sciences, University of Bristol, Clifton, UK
⁴Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA
Published by arrangement with John Wiley & Sons

The shergottites are the largest group of Martian meteorites, and the only group that has not been found to contain definitive evidence of Martian aqueous alteration. Given recent reports of current liquid water at the surface of Mars, this study aimed to investigate in detail the possibility of Martian phyllosilicate within shergottite Dhofar 019. Optical and scanning electron microscopy, followed by transmission electron microscopy, confirmed the presence of alteration orangettes, with a layered structure consisting of poorly ordered Mg-phyllosilicate and calcite. These investigations identified maskelynite dissolution, followed by Mg-phyllosilicate and calcite deposition within the dissolution pits, as the method of orangette production. The presence of celestine within the orangette layers, the absence of shock dislocation features within calcite, and the Mg-rich nature of the phyllosilicate, all indicate a terrestrial origin for these features on Dhofar 019.

¹Chi Ma,²Oliver Tschauner,¹John R. Beckett,¹George R. Rossman,³Clemens Prescher,³Vitali B. Prakapenka,⁴Hans A. Bechtel,⁴Alastair MacDowell
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13000]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
²High Pressure Science and Engineering Center and Department of Geoscience, University of Nevada, Las Vegas, Nevada, USA
³Center of Advanced Radiation Sources, GSECARS, The University of Chicago, Chicago, Illinois, USA
⁴Advanced Light Source, ESG, Lawrence Berkeley National Laboratory, Berkeley, California, USA
Published by arrangement with John Wiley & Sons

In this paper, we discuss the occurrence of liebermannite (IMA 2013-128), KAlSi3O8, a new, shock-generated, high-pressure tetragonal hollandite-type structure silicate mineral, in the Zagami basaltic shergottite meteorite. Liebermannite crystallizes in space group I4/m with Z = 2, cell dimensions of a = 9.15 ± 0.14 (1σ) Å, c = 2.74 ± 0.13 Å, and a cell volume of 229 ± 19 Å3 (for the type material), as revealed by synchrotron diffraction. In Zagami, liebermannite likely formed via solid-state transformation of primary igneous K-feldspar during an impact event that achieved pressures of ~20 GPa or more. The mineral name is in honor of Robert C. Liebermann, a high-pressure mineral physicist at Stony Brook University, New York, USA.

¹Carl Palk,¹Rasmus Andreasen,¹Mark Rehkämper,¹Alison Stunt,¹Katharina Kreissig,¹Barry Coles,²Maria Schönbächler,³Caroline Smith
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12989]
¹Department of Earth Science & Engineering, Imperial College London, London, UK
²Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
³Department of Mineralogy, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

New Tl, Pb, and Cd concentration and Tl, Pb isotope data are presented for enstatite as well as L- and LL-type ordinary chondrites, with additional Cd stable isotope results for the former. All three chondrite suites have Tl and Cd contents that vary by more than 1–2 orders of magnitude but Pb concentrations are more uniform, as a result of terrestrial Pb contamination. Model calculations based on Pb isotope compositions indicate that for more than half of the samples, more than 50% of the measured Pb contents are due to addition of modern terrestrial Pb. In part, this is responsible for the relatively young and imprecise Pb-Pb ages determined for EH, L, and LL chondrites, which are hence only of limited chronological utility. In contrast, four particularly pristine EL chondrites define a precise Pb-Pb cooling age of 4559 ± 6 Ma. The enstatite chondrites (ECs) have highly variable ε114/110Cd of between about +3 and +70 due to stable isotope fractionation from thermal and shock metamorphism. Furthermore, nearly all enstatite meteorites display ε205Tl values from −3.3 to +0.8, while a single anomalous sample is highly fractionated in both Tl and Cd isotopes. The majority of the ECs thereby define a correlation of ε205Tl with ε114/110Cd, which suggests that at least some of the Tl isotope variability reflects stable isotope fractionation rather than radiogenic ingrowth of 205Tl from 205Pb decay. Considering L chondrites, most ε205Tl values range between −4 and +1, while two outliers with ε205Tl ≤ −10 are indicative of stable isotope fractionation. Considering only those L chondrites which are least likely to feature Pb contamination or stable Tl isotope effects, the results are in accord with the former presence of live 205Pb on the parent body, with an initial 205Pb/204Pb = (1.5 ± 1.4) × 10−4, which suggests late equilibration of the Pb-Tl system 26–113 Ma after carbonaceous chondrites (CCs). The LL chondrites display highly variable ε205Tl values from −12.5 to +14.9, also indicative of stable isotope effects. However, the data for three pristine LL3/LL4 chondrites display an excellent correlation between ε205Tl and 204Pb/203Tl. This defines an initial 205Pb/204Pb of (1.4 ± 0.3) × 10−4, equivalent to a 205Pb-205Tl cooling age of 55 + 12/−24 Ma (31–67 Ma) after CCs.

¹E. A. Pilles,^1,2G. R. Osinski,¹R. A. F. Grieve,³D. A. Smith,³J. M. Bailey
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12986]
¹Department of Earth Sciences/Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, Canada
²Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada
³Wallbridge Mining Company Limited, Sudbury, Ontario, Canada
Published by arrangement with John Wiley & Sons

Offset dikes are found concentrically around—and extending radially outward from—the Sudbury Igneous Complex (SIC), which represents an ~3 km thick differentiated impact melt sheet. The dikes are typically composed of an inclusion-rich, so-called quartz diorite (IQD) in the center of the dike, and an inclusion-poor quartz diorite (QD) along the margins of the dike. New exposures of the intersection between the concentric Hess and radial Foy offset dikes provide an excellent opportunity to understand the relationship between the radial and concentric offset dikes and their internal phases. The goal was to constrain the timing of the dike emplacements relative to the impact and formation of the SIC. Results herein suggest that (1) the timing between the emplacement of the QD and IQD melts was geologically short, (2) the Hess and Foy dikes coexisted as melts at the same time and the intersection between them represents a mixture of the two, (3) the Foy dike has a slightly more evolved chemical composition than the Hess dike, and (4) the IQD melt from the Foy dike underwent some degree of chemical fractionation after its initial emplacement.