¹Breanne L. Berg, ¹Edward A. Cloutis, ²Pierre Beck, ³Pierre Vernazza, ⁴Janice L. Bishop, ⁵Driss Takir, ⁶Vishnu Reddy, ¹Daniel Applin, ¹Paul Mann
¹Department of Geography, University of Winnipeg, Winnipeg, MB, Canada R3B 2E9
²Université de Grenoble Alpes, IPAG, F-38000 Grenoble, France
³Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁴SETI Institute, 89 Bernardo Ave, Suite 100, Mountain View, CA, USA 94043
⁵Astrogeology Science Center, United States Geological Survey, 2255 N. Gemini Dr., Flagstaff, AZ, 86001, USA
⁶Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ, USA 85719-2395

Ammonium-bearing minerals have been suggested to be present on Mars, Ceres, and various asteroids and comets. We undertook a systematic study of the spectral reflectance properties of ammonium-bearing minerals and compounds that have possible planetary relevance (i.e., ammonium carbonates, chlorides, nitrates, oxalates, phosphates, silicates, and sulfates). Various synthetic and natural NH4+-bearing minerals were analyzed using reflectance spectroscopy in the long-wave ultraviolet, visible, near-infrared, and mid-infrared regions (0.35-8 μm) in order to identify spectral features characteristic of the NH4+ molecule, and to evaluate if and how these features vary among different species. Mineral phases were confirmed through structural and compositional analyses using X-ray diffraction, X-ray fluorescence, and elemental combustion analysis. Characteristic absorption features associated with NH4 can be seen in the reflectance spectra at wavelengths as short as ∼1 μm. In the near-infrared region, the most prominent absorption bands are located near 1.6, 2.0, and 2.2 μm. Absorption features characteristic of NH4+ occurred at slightly longer wavelengths in the mineral-bound NH4+ spectra than for free NH4+ for most of the samples. Differences in wavelength position are attributable to various factors, including differences in the type and polarizability of the anion(s) attached to the NH4+, degree and type of hydrogen bonding, molecule symmetry, and cation substitutions. Multiple absorption features, usually three absorption bands, in the mid-infrared region between ∼2.8 and 3.8 μm were seen in all but the most NH4-poor sample spectra, and are attributed to fundamentals, combinations, and overtones of stretching and bending vibrations of the NH4+ molecule. These features appear even in reflectance spectra of water-rich samples which exhibit a strong 3 μm region water absorption feature. While many of the samples examined in this study have NH4 absorption bands at unique wavelength positions, in order to discriminate between different NH4+-bearing phases, absorption features corresponding to molecules other than NH4+ should be included in spectral analysis. A qualitative comparison of the laboratory results to telescopic spectra of asteroids 1 Ceres, 10 Hygiea, and 324 Bamberga for the 3 μm region demonstrates that a number of NH4-bearing phases are consistent with the observational data in terms of exhibiting an absorption band in the 3.07 μm region.

Reference
Berg BL, Cloutis EA, Beck P, Vernazza P, Bishop JL, Takir D, Reddy V, Applin D, Mann P (2015) Reflectance spectroscopy (0.35-8 μm) of ammonium-bearing minerals and qualitative comparison to Ceres-like asteroids. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.10.028]
Copyright Elsevier

¹Takuya Fujiyoshi, ²Christopher M. Wright,³ Toby J. T. Moore
¹Subaru Telescope, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 650 North A’ohoku Place, Hilo, HI 96720, USA
²School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, PO Box 7916, Canberra BC ACT 2610, Australia
³Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK

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Reference
Fujiyoshi T, Wright CM, Moore TJT (2015) Mid-infrared spectroscopy of SVS13: silicates, quartz and SiC in a protoplanetary disc. Monthly Noticles of the Royla Astronomical Society 451, 3371-3384.
Link to Article [doi: 10.1093/mnras/stv1171]

¹M. Ali-Dib, ²R. G. Martin, ¹J.-M. Petit, ³O. Mousis, ³P. Vernazza, ⁴J. I. Lunine
¹Institut UTINAM, CNRS-UMR 6213, Observatoire de Besançon, Université de Franche-Comté, BP 1615, 25010 Besançon Cedex, France
e-mail: mdib@obs-besancon.fr
²Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154, USA
³Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁴Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA

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Reference
Ali-Dib M, Martin RG, Petit J-M, Mousis O, Vernazza P, Lunine JI (2015) Nebular dead zone effects on the D/H ratio in chondrites and comets. Astronomy & Astrophysics 583, A58
Link to Article [http://dx.doi.org/10.1051/0004-6361/201526453]

^1,2L. Spina et al. (>10)*
¹Departamento de Astronomia do IAG/USP, Universidade de São Paulo, Rua do Mãtao 1226, São Paulo, 05509-900 SP, Brasil
e-mail: lspina@usp.br
²INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
*Find the extensive, full author and affiliation list on the publishers website

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Reference
Spina L. et al. (2015) The Gaia-ESO Survey: chemical signatures of rocky accretion in a young solar-type star. Astronomy & Astrophysics 582, L6
Link to Article [http://dx.doi.org/10.1051/0004-6361/201526896 ]

^1,2Cindy L. Young, ¹James J. Wray, ³Roger N. Clark, ⁴John R. Spencer, ⁵Donald E. Jennings, ⁶Kevin P. Hand, ⁷Michael J. Poston, ⁶Robert W. Carlson
¹School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
²Emory University, Atlanta, GA, USA
³Planetary Science Institute, Tucson, AZ, USA
⁴Southwest Research Institute, Boulder, CO, USA
⁵NASA Goddard Space Flight Center, Greenbelt, MD, USA
⁶Jet Propulsion Laboratory, Pasadena, CA, USA
⁷Caltech, Pasadena, CA, USA

We present the first spectral features obtained from Cassini’s Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal-to-noise ratios (S/Ns) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/N and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ~855 cm−1 and a possible doublet at 660 and 690 cm−1 that do not correspond to any known instrument artifacts. We attribute the 855 cm−1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn’s icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm−1. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125 K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm−1 and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.

Reference
Young CL, Wray JJ, Clark RN, Spencer JR, Jennings DE, Hand KP, Poston MJ, Carlson RW (2015) SILICATES ON IAPETUS FROM CASSINI’S COMPOSITE INFRARED SPECTROMETER. Astrophysical Journal Letters 811, L27
Link to Article [http://dx.doi.org/10.1088/2041-8205/811/2/L27]

¹Takaya Nozawa, ²Shigeru Wakita, ^1,4Yasuhiro Hasegawa, ³Takashi Kozasa
¹Division of Theoretical Astronomy, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
²Center for Computational Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
³Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan

A few particles of presolar Al2O3 grains with sizes above 0.5 μm are believed to have been produced in the ejecta of core-collapse supernovae (SNe). In order to clarify the formation condition of such large Al2O3 grains, we investigate the condensation of Al2O3 grains for wide ranges of the gas density and cooling rate. We first show that the average radius and condensation efficiency of newly formed Al2O3 grains are successfully described by a non-dimensional quantity ${{\rm{\Lambda }}}_{{\rm{on}}}$, defined as the ratio of the timescale with which the supersaturation ratio increases to the collision timescale of reactant gas species at dust formation. Then we find that the formation of submicron-sized Al2O3 grains requires at least 10 times higher gas densities than those presented by one-dimensional SN models. This indicates that presolar Al2O3 grains identified as having their origin in SNe might be formed in dense gas clumps, allowing us to propose that the measured sizes of presolar grains can be a powerful tool for constraining the physical conditions in which they formed. We also briefly discuss the survival of newly formed Al2O3 grains against destruction in the shocked gas within SN remnants.

Reference
Nozawa T, Wakita S, Hasegawa Y, Kozasa T (2015) PROBING THE PHYSICAL CONDITIONS OF SUPERNOVA EJECTA WITH THE MEASURED SIZES OF PRESOLAR Al2O3 GRAINS. Astrophysical Journal Letters 811, L39
Link to Article [http://dx.doi.org/10.1088/2041-8205/811/2/L39]

¹Philip. J. Carter, ¹Zoë. M. Leinhardt, ²Tim Elliott, ²Michael J. Walter, ³Sarah T. Stewart
¹School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK
²School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, UK
³Department of Earth and Planetary Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA

The Earth appears non-chondritic in its abundances of refractory lithophile elements, posing a significant problem for our understanding of its formation and evolution. It has been suggested that this non-chondritic composition may be explained by collisional erosion of differentiated planetesimals of originally chondritic composition. In this work, we present N-body simulations of terrestrial planet formation that track the growth of planetary embryos from planetesimals. We simulate evolution through the runaway and oligarchic growth phases under the Grand Tack model and in the absence of giant planets. These simulations include a state-of-the-art collision model that allows multiple collision outcomes, such as accretion, erosion, and bouncing events, and enables tracking of the evolving core mass fraction of accreting planetesimals. We show that the embryos grown during this intermediate stage of planet formation exhibit a range of core mass fractions, and that with significant dynamical excitation, enough mantle can be stripped from growing embryos to account for the Earth’s non-chondritic Fe/Mg ratio. We also find that there is a large diversity in the composition of remnant planetesimals, with both iron-rich and silicate-rich fragments produced via collisions.

Reference
Carter PJ, Leinhardt ZM, Elliott T, Walter MJ, Stewart ST (2015) COMPOSITIONAL EVOLUTION DURING ROCKY PROTOPLANET ACCRETION. Astrophysical Journal 813, 72
Link to Article [http://dx.doi.org/10.1088/0004-637X/813/1/72]

^1,2Vishnu Reddy et al. (>10)*
¹Planetary Science Institute, 1700 East Fort Lowell Road, Tucson, AZ 85719, USA
²Visiting Astronomer at the Infrared Telescope Facility
*Find the extensive, full author and affiliation list on the publishers website

The physical characterization of potentially hazardous asteroids (PHAs) is important for impact hazard assessment and evaluating mitigation options. Close flybys of PHAs provide an opportunity to study their surface photometric and spectral properties that enable the identification of their source regions in the main asteroid belt. We observed PHA (357439) 2004 BL86 during a close flyby of the Earth at a distance of 1.2 million km (0.0080 AU) on 2015 January 26, with an array of ground-based telescopes to constrain its photometric and spectral properties. Lightcurve observations showed that the asteroid was a binary and subsequent radar observations confirmed the binary nature and gave a primary diameter of 300 m and a secondary diameter of 50–100 m. Our photometric observations were used to derive the phase curve of 2004 BL86 in the V-band. Two different photometric functions were fitted to this phase curve, the IAU H–G model and the Shevchenko model. From the fit of the H–G function we obtained an absolute magnitude of H = 19.51 ± 0.02 and a slope parameter of G = 0.34 ± 0.02. The Shevchenko function yielded an absolute magnitude of H = 19.03 ± 0.07 and a phase coefficient b = 0.0225 ± 0.0006. The phase coefficient was used to calculate the geometric albedo (Ag) using the relationship found by Belskaya & Schevchenko, obtaining a value of Ag = 40% ± 8% in the V-band. With the geometric albedo and the absolute magnitudes derived from the H–G and the Shevchenko functions we calculated the diameter (D) of 2004 BL86, obtaining D = 263 ± 26 and D = 328 ± 35 m, respectively. 2004 BL86 spectral band parameters and pyroxene chemistry are consistent with non-cumulate eucrite meteorites. A majority of these meteorites are derived from Vesta and are analogous with surface lava flows on a differentiated parent body. A non-diagnostic spectral curve match using the Modeling for Asteroids tool yielded a best-match with non-cumulate eucrite Bereba. Three other near-Earth asteroids (1993 VW, 1998 KK17, and 2000 XH44) that were observed by Burbine et al. also have spectral properties similar to 2004 BL86. The presence of eucrites with anomalous oxygen isotope ratios compared to the howardites, eucrites, and diogenites meteorites from Vesta suggests the possible presence of multiple differentiated bodies in the inner main belt or the contamination of Vesta’s surface with exogenic material. The spectral properties of both anomalous and Vestan eucrites are degenerate, making it difficult to identify the parent bodies of anomalous eucrites in the main belt and the NEO population using remote sensing. This makes it difficult to link 2004 BL86 directly to Vesta, although the Vesta family is the largest contributor of V-types to near-Earth space.

Reference
Reddy V et al. (2015) THE PHYSICAL CHARACTERIZATION OF THE POTENTIALLY HAZARDOUS ASTEROID 2004 BL86: A FRAGMENT OF A DIFFERENTIATED ASTEROID. Astrophysical Journal (in Press)
Link to Article [http://dx.doi.org/10.1088/0004-637X/811/1/65]

¹Pia Friend,^1,2Dominik C. Hezel, ¹Daniel Mucerschi
¹University of Cologne, Department of Geology and Mineralogy, Zülpicher Str. 49b, 50674 Köln, Germany
²Natural History Museum, Department of Mineralogy, Cromwell Road, SW7 5BD, London, UK

We studied the texture of 256 chondrules in thin sections of 16 different carbonaceous (CV, CR, CO, CM, CH) and Rumuruti chondrites. In a conservative count ∼75% of all chondrules are mineralogically zoned, i.e. these chondrules have an olivine core, surrounded by a low-Ca pyroxene rim. A realistic estimate pushes the fraction of zoned chondrules to >90% of all chondrules. Mineralogically zoned chondrules are the dominant and typical chondrule type in carbonaceous and Rumuruti chondrites. The formation of the mineralogical zonation represents a fundamentally important process of chondrule formation. The classic typification of chondrules into PO, POP and PP might in fact represent different sections through mineralogically zoned chondrules. On average, the low-Ca pyroxene rims occupy 30 vol.% of the entire chondrule. The low-Ca pyroxene most probably formed by reaction of an olivine rich chondrule with SiO from the surrounding gas. This reaction adds 3-15 wt.% of material, mainly SiO2, to the chondrule. Chondrules were open systems and interacted substantially with the surrounding gas. This is in agreement with many previous studies on chondrule formation. This open system behaviour and the exchange of material with the surrounding gas can explain bulk chondrule compositional variations in a single meteorite and supports the findings from complementarity that chondrules and matrix formed from the same chemical reservoir.

Reference
Friend P, Hezel DC, Mucerschi D (2015) The conditions of chondrule formation, Part II: Open System. Geochimica et Cosmochimica (in Press)
Link to Article [doi:10.1016/j.gca.2015.10.026]
Copyright Elsevier

¹A. K. Speck, ^2,3K. M. Pitman, ⁴A. M. Hofmeister
¹Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, MO 65211, USA
²Planetary Science Institute, Tucson, AZ 85719, USA
³Space Science Institute, Boulder, CO 80301, USA
⁴Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA

“Astronomical” or “circumstellar” silicate optical functions (real and imaginary indices of refraction $n(\lambda )$ and $k(\lambda )$) have previously been derived from compositionally and structurally disparate samples; past values were compiled from different sources in the literature, and are essentially kluges of observational, laboratory, and extrapolated or interpolated values. These synthetic optical functions were created because astronomers lack the quantitative data on amorphous silicates at all wavelengths needed for radiative transfer modeling. This paper provides optical functions that (1) are created with a consistent methodology, (2) use the same sample across all wavelengths, and (3) minimize interpolation and extrapolation wherever possible. We present electronic data tables of optical functions derived from mid-ultraviolet to far-infrared (FIR) laboratory transmission spectra for two materials: iron-free glass with chondritic/solar atmospheric abundances, and metallic iron. We compare these optical functions to other popular n, k data used to model amorphous silicates (e.g., “astronomical” or “circumstellar” silicate), both directly and in application to a simple system: the dust shell of the post-AGB star HD 161796. Using the new optical functions, we find that the FIR profile of model spectral energy distributions are significantly affected by the ratio of glass to iron. Our case study on HD 161796 shows that in modeling with our new optical functions, the mineralogy is markedly different from that derived using synthetic optical functions and suggests a new scenario of crystalline silicate formation.

Reference
Speck AK, Pitman KM, Hofmeister AM (2015) Better Alternatives to “Astronomical Silicate”: Laboratory-Based Optical Functions of Chondritic/Solar Abundance Glass with Application to HD161796. The Astrophysical Journal 809
Link to Article [http://dx.doi.org/10.1088/0004-637X/809/1/65]