¹N. van der Marel, ¹P. Pinilla, ^1,3J. Tobin, ¹T. van Kempen, ²S. Andrews, ²L. Ricci, ²T. Birnstiel
¹Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
²Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
³VENI fellow.

Azimuthally asymmetric dust distributions observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in transition disks have been interpreted as dust traps. We present Very Large Array Ka band (34 GHz or 0.9 cm) and ALMA Cycle 2 Band 9 (680 GHz or 0.45 mm) observations at a 0farcs2 resolution of the Oph IRS 48 disk, which suggest that larger particles could be more azimuthally concentrated than smaller dust grains, assuming an axisymmetric temperature field or optically thin 680 GHz emission. Fitting an intensity model to both data demonstrates that the azimuthal extent of the millimeter emission is 2.3 ± 0.9 times as wide as the centimeter emission, marginally consistent with the particle trapping mechanism under the above assumptions. The 34 GHz continuum image also reveals evidence for ionized gas emission from the star. Both the morphology and the spectral index variations are consistent with an increase of large particles in the center of the trap, but uncertainties remain due to the continuum optical depth at 680 GHz. Particle trapping has been proposed in planet formation models to allow dust particles to grow beyond millimeter sizes in the outer regions of protoplanetary disks. The new observations in the Oph IRS 48 disk provide support for the dust trapping mechanism for centimeter-sized grains, although additional data are required for definitive confirmation.

Reference
van der Marel N, Pinilla P, Tobin J, van Kempen T, Andrews S, L. Ricci2, Birnstiel T (2015) A CONCENTRATION OF CENTIMETER-SIZED GRAINS IN THE OPHIUCHUS IRS 48 DUST TRAP. Astrophysical Journal Letters 810, L7
Link to Article [http://dx.doi.org/10.1088/2041-8205/810/1/L7]

^1,2Matthieu Gounelle
¹IMPMC, Muséum National d’Histoire Naturelle, Sorbonne Universités, CNRS, UPMC & IRD, 57 rue Cuvier, 75005 Paris, France
e-mail: gounelle@mnhn.fr
²Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France

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Reference
Gounelle M et al. (2015) The abundance of 26Al-rich planetary systems in the Galaxy. Astronomy & Astrophysics 582, A26
Link to Article [http://dx.doi.org/10.1051/0004-6361/201526174]

¹Povinec, P.P., ¹Sýkora, I., ¹Kováčik, A., ^2,3Koeberl, C.
¹Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynská dolina F-1, Bratislava, Slovakia
²Natural History Museum, Burgring 7, Vienna, Austria
³Department of Lithospheric Research, University of Vienna, Vienna, Austria

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Reference
Povinec PP, Sýkora I, Kováčik A, Koeberl C (2015) High-sensitivity HPGe gamma-spectrometry analysis of radionuclides in Martian meteorites. Journal of Radioanalytical and Nuclear Chemistry (in Press)
Link to Article [DOI: 10.1007/s10967-015-4523-5]

¹Josh Wimpenny, ²Yuri Amelin, ¹Qing-zhu Yin
¹Department of Earth and Planetary Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
²Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

Studies of Lu–Hf isotope systematics in meteorites have produced apparent “ages” that are older than Pb–Pb ages and older than the estimated age of our solar system. One proposed explanation for this discrepancy is that irradiation by cosmic rays caused excitation of 176Lu to its short-lived isomer that then underwent rapid decay to 176Hf. This explanation can account for apparent excesses in 176Hf that correlate with Lu/Hf ratio. Mass balance requires that samples with measurable excess in 176Hf should also have measurable deficiencies in 176Lu on the order of 1‰–3‰. To unambiguously test the accelerated decay hypothesis, we have measured the 176Lu/175Lu ratio in terrestrial materials and achondrites to search for evidence of depletion in 176Lu. To a precision of 0.1‰ terrestrial standards, cumulate and basaltic eucrites and angrites all have the same 176Lu/175Lu ratio. Barring a subsequent mass-dependent fractionation event, these results suggest that the apparent excesses in 176Hf are not caused by accelerated decay of 176Lu, and so another hypothesis is required to explain apparently old Lu–Hf ages.

Reference
Wimpenny J, Amelin Y, Y Qing-zhu Yin (2015) THE LU ISOTOPIC COMPOSITION OF ACHONDRITES: CLOSING THE CASE FOR ACCELERATED DECAY OF 176LU. Astrophysical Journal Letters 812, L3
Link to Article [http://dx.doi.org/10.1088/2041-8205/812/1/L3]

¹F.J.M. Rietmeijer, ²V. Della Corte, ²M. Ferrari, ^2,3A. Rotundi, ⁴R. Brunetto
¹Department of Earth and Planetary Sciences, MSC03 2040, 1-University of New Mexico, Albuquerque, NM 87131-0001, USA
²Istituto di Astrofisica e Planetologia Spaziali – INAF, Via del Fosso del Cavaliere, 100, 00133, Roma, Italy
³Dipartimento di Scienze Applicate, Università degli Studi di Napoli “Parthenope”, CDN, I C4, 80143, Napoli, Italy
⁴Institut d’Astrophysique Spatiale, CNRS, UMR-8617, Université Paris-Sud, bâtiment 121, F-91405 Orsay Cedex, France

Bolide and fireball fragmentation produce vast amounts of dust that will slowly fall through the stratosphere. DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval) was designed to intercept the nanometer to micrometer meteoric dust from these events for laboratory analyses while it is still in the upper stratosphere. This effort required extraordinary precautions to avoid particle contamination during collection and in the laboratory. Here we report dust from the upper stratosphere that was collected during two campaigns one in 2008 and another in 2011. We collected and characterized forty five uncontaminated meteoric dust particles. The collected particles are alumina, aluminosilica, plagioclase, fassaite, silica, CaCO3, CaO, extreme F-rich C-O-Ca particles, and oxocarbon particles. These particles are found in friable CI and CM carbonaceous chondrite, and unequilibrated ordinary chondrite meteoroids that are the most common source of bolides and fireballs. The oxocarbons have no meteorite counterparts. Some F-bearing CaCO3 particles changed shape when they interacted with the ambient laboratory atmosphere which might indicate their highly unequilibrated state as a result of fragmentation. Equilibrium considerations constrain the thermal regime experienced by the collected particles between ∼2000°C and ∼1000°C, as high as 3,700°C and as low as ∼650°C after 9 secs, followed by rapid quenching (μs) to below 1,600°C, but equilibrium conditions during these events is most unlikely. So far the observed thermal conditions in these events put the temperatures between ∼4,300°C and ∼430°C for 5 seconds and high cooling rates. Such conditions are present in the immediate wake of meteors and fireballs.

Reference
Rietmeijer FJM, Della Corte V, Ferrari M, Rotundi A, Brunetto R (2015) Laboratory Analyses of Meteoric Debris in the Upper stratosphere from Settling Bolide Dust Clouds. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.11.003]
Copyright Elsevier

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]