¹Evan E. Groopman, ¹Kenneth S. Grabowski, ²Albert J. Fahey, ³Levke Kööp
Journal of Analytical Atomic Spectrometry 32, 2153-2163 Link to Article [DOI: 10.1039/C7JA00294G]
¹Materials Science and Technology Division, U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, USA
²Microscopy & Surface Analysis, Corning, Inc., Corning, USA
³Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave., Chicago, USA

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

^1,2Noël Chaumard,³Munir Humayun,¹Brigitte Zanda,^1,4Roger H. Hewins
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13040]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Universités, Muséum national d’histoire naturelle, UPMC Université Paris 06, UMR CNRS 7590, IRD, UMR 206, Paris Cedex 05, France
²Department of Geoscience, WiscSIMS, University of Wisconsin-Madison, Madison, Wisconsin, USA
³Department of Earth, Ocean & Atmospheric Science, and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA
⁴Department of Earth & Planetary Sciences, Rutgers University, Piscataway, New Jersey, USA
Published by arrangement with John Wiley & Sons

Cooling rates are one of the few fundamental constraints on models of chondrule formation. In this study, we used Cu and Ga diffusion profiles in metal grains to determine the cooling rates of type I chondrules in the Renazzo CR2 chondrite. To improve previous estimations of cooling rates obtained using this method, we used CT scanning and serial polishing of our sections to analyze equatorial sections of large metal grains. Through the cores of these metal grains situated at the surface of chondrules, the cooling rates calculated range from 21 to 86 K h−1 for a peak temperature Tp ~ 1623–1673 K. A metal grain embedded in the core of a chondrule exhibits a cooling rate of 1.2 K h−1 at a Tp ~ 1573 K. We also measured Cu-Ga diffusion profiles from nonequatorial sections of metal grains and calculated a lower range of cooling rates of 15–69 K h−1 for Tp ~ 1473–1603 K compared to our results from equatorial sections. The high cooling rates inferred from the lightning model (several thousand K h−1) are clearly at odds with the values obtained in this work. The X-wind model predicts cooling rates (~6–10 K h−1) lower than most of our results. The cooling rates calculated here are in close agreement with those inferred from shock wave models, in particular for temperatures at which olivine crystallizes (from ~10 to several hundreds K h−1 between 1900 and 1500 K). However, the chemical compositions of metal grains in Renazzo are consistent with the splashing model, in which a spray of metal droplets originated from a partially molten planetesimal. Volatile siderophile element depletion is explained by evaporation before metal was engulfed within silicate droplets. Liquid metal isolated from the liquid silicate crystallized during cooling, reacted with the ambient gas, and then re-accreted within partially molten chondrules.

¹R. J. Charles,¹Pierre-Yves F. Robin,¹Donald W. Davis,^1,2,3Phil J. A. McCausland
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13038]
¹Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
²Centre for Planetary Science and Exploration, Western University, London, Ontario, Canada
³Western Paleomagnetic and Petrophysical Laboratory, Western University, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

The approximately spherical shapes of chondrules has long been attributed to surface tension acting on ~1 mm melt droplets that formed and cooled in the microgravity field of the solar nebula. However, chondrule shapes commonly depart significantly from spherical. In this study, 109 chondrules in a sample of CR2 chondrite NWA 801 were imaged by X-ray computed tomography and best-fitted to ellipsoids. The analysis confirms that many chondrules are indeed not spherical, and also that the chondrules’ collective shape fabric records a definite 13% compaction in the host meteorite. Dehydration of phyllosilicates within chondrules may account for that strain. However, retro-deforming all chondrules shows that a large majority were already far from spherical prior to accretion. Possible models for these initial shapes include prior deformation of individual chondrules in earlier hosts, and, as suggested by previous authors, rotation of chondrules as they were solidifying, and/or “streaming” of molten chondrules by their differential velocities with their gaseous hosts after melting. More in situ 3-D work such as this study on a variety of unequilibrated chondrites, combined with detailed structural petrography, should help further constrain these models and refine our understanding of chondrite formation.

¹Caio Vinícius Gabrig Turbay Rangel, ²Marcos Tadeu D’Azeredo Orlando, ³Cláudio De Morisson Valeriano, ⁴Alexandre de Oliveira Chaves
International Geology Review 59, 1966-1973 Link to Article [https://doi.org/10.1080/00206814.2017.1308842]
¹Geology Department, Universidade Federal do Espirito Santo, Alegre, Brasil
²Department of Physics, Universidade Federal do Espirito Santo, Alegre, Brasil
³TECTO, Universidade do Estado Rio de Janiero, Rio de Janiero, Brazil
⁴ICG, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

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

¹A.B.Verchovsky
Geochemistry International 55, 957-970 Link to Article [https://doi.org/10.1134/S0016702917110106]
¹School of Physical Sciences STEM, The Open University, Walton Hall Milton Keynes United Kingdom

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

¹Bruno L. do Nascimento-Dias,^1,2Davi F. de Oliveira,²Alessandra S. Machado,²Olga M.O. Araújo,²Ricardo T. Lopes,²Marcelino J. dos Anjos
X-Ray Spectrometry 47, 86-91 Link to Article [DOI: 10.1002/xrs.2815]
¹Physics Institute Armando Dias Tavares, University of State of Rio de Janeiro, Rio de Janeiro, Brazil
²Nuclear Instrumentation Laboratory, PEN, COPPE, UFRJ, Rio de Janeiro, Brazil

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

^1,2H.Zhang et al. (>10)
Applied Physics Letters 111, 184104 Link to Article [https://doi.org/10.1063/1.5010050]
¹State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
²University of Chinese Academy of Sciences, Beijing 100049, China

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

^1,2T Loylip, ^2,3S Wannawichian
Journal of Physics: Conference Series 901, 012005 Link to Article [https://doi.org/10.1088/1742-6596/901/1/012005]
¹Graduate School, Chiang Mai University, Chiang Mai, Thailand
²National Astronomical Research Institute of Thailand (NARIT), Chiang Mai, Thailand
³Department of physics and Materials Science, Chiang Mai University, Chiang Mai, Thailand

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

¹Jean-Philippe Combe et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.12.039]
¹Bear Fight Institute, 22 Fiddler’s Road, P.O. Box 667, Winthrop, WA 98862, USA
Copyright Elsevier

We studied the surface composition of Ceres within the limits of the Ezinu quadrangle in the ranges 180 – 270°E and 21 – 66°N by analyzing data from Dawn’s visible and near-infrared data from the Visible and InfraRed mapping spectrometer and from multispectral images from the Framing Camera. Our analysis includes the distribution of hydroxylated minerals, ammoniated phyllosilicates, carbonates, the search for organic materials and the characterization of physical properties of the regolith. The surface of this quadrangle is largely homogenous, except for small, high-albedo carbonate-rich areas, and one zone on dark, lobate materials on the floor of Occator, which constitute the main topics of investigation. 1) Carbonate-rich surface compositions are associated with H2O ice rich crust. Weaker absorption bands of hydroxylated and ammoniated minerals over the carbonate-rich areas can be explained by higher abundances of carbonates at the topmost surface. 2) Dark, smooth lobate materials at the foot of Occator’s northeastern wall possibly reveal fresh slumping of phyllosilicate-rich materials with fine grain size, or local enrichment in carbon-rich materials such as tholins. 3) The deeper absorption band depth of OH and NH4, on the rim of several impact craters, is one observation that is consistent with a stratification of the phyllosilicate abundance that has been inferred previously from global investigations.

^1,2M.Devogèle et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.12.026]
¹Université de Liège, Space sciences, Technologies and Astrophysics Research (STAR) Institute, Allée du 6 Août 19c, Sart Tilman, 4000 Liège, Belgium
²Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange UMR7293, Nice, France
Copyright Elsevier

Asteroids can be classified into several groups based on their spectral reflectance. Among these groups, the one belonging to the L-class in the taxonomic classification based on visible and near-infrared spectra exhibit several peculiar properties. First, their near-infrared spectrum is characterized by a strong absorption band interpreted as the diagnostic of a high content of the FeO bearing spinel mineral. This mineral is one of the main constituents of Calcium-Aluminum-rich Inclusions (CAI) the oldest mineral compounds found in the solar system. In polarimetry, they possess an uncommonly large value of the inversion angle incompatible with all known asteroid belonging to other taxonomical classes. Asteroids found to possess such a high inversion angle are commonly called Barbarians based on the first asteroid on which this property was first identified, (234) Barbara. In this paper we present the results of an extensive campaign of polarimetric and spectroscopic observations of L-class objects. We have derived phase-polarization curves for a sample of 7 Barbarians, finding a variety of inversion angles ranging between 25 and 30°. Spectral reflectance data exhibit variations in terms of spectral slope and absorption features in the near-infrared. We analyzed these data using a Hapke model to obtain some inferences about the relative abundance of CAI and other mineral compounds. By combining spectroscopic and polarimetric results, we find evidence that the polarimetric inversion angle is directly correlated with the presence of CAI, and the peculiar polarimetric properties of Barbarians are primarily a consequence of their anomalous composition.