^1,2,3Kasia Biron, ^1,2Sylvie Derenne, ³François Robert, ⁴Jean-Noël Rouzaud
¹CNRS, UMR 7619 METIS, Paris, France
²Sorbonne Universités, UPMC Univ Paris 06, CNRS, EPHE, UMR 7619 METIS, Paris, France
³IMPMC, CNRS/MNHN UMR 7202, Paris, France
⁴Laboratoire de Géologie, ENS/CNRS UMR 8538, Paris, France

Based on the statistical model proposed for the molecular structure of the insoluble organic matter (IOM) isolated from the Murchison meteorite, it was recently proposed that, in the solar T-Tauri disk regions where (photo)dissociation of gaseous molecules takes place, aromatics result from the cyclization/aromatization of short aliphatics. This hypothesis is tested in this study, with n-alkanes being submitted to high-frequency discharge at low pressure. The contamination issue was eliminated using deuterated precursor. IOM was formed and studied using solid-state nuclear magnetic resonance, pyrolysis coupled to gas chromatography and mass spectrometry, RuO4 oxidation, and high-resolution transmission electron microscopy. It exhibits numerous similarities at the molecular level with the hydrocarbon backbone of the natural IOM, reinforcing the idea that the initial precursors of the IOM were originally chains in the gas. Moreover, a fine comparison between the chemical structure of several meteorite IOM suggests either that (i) the meteorite IOMs share a common precursor standing for the synthetic IOM or that (ii) the slight differences between the meteorite IOMs reflect differences in their environment at the time of their formation i.e., related to plasma temperature that, in turn, dictates the dissociation–recombination rates of organic fragments.

Reference
Biron K, Derenne S, Robert F, Rouzaud J-N (2015) Toward an experimental synthesis of the chondritic insoluble organic matter. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12477]

Published by arrangement with John Wiley & Sons

¹Charles A Schambeau, ¹Yanga R. Fernández, ²Carey M. Lisse, ³Nalin Samarasinha, ⁴Laura M. Woodney
¹Department of Physics, University of Central Florida, Orlando, FL 32816, USA
²Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723
³Planetary Science Institute, Tucson, AZ 85719, USA
⁴Department of Physics, California State University San Bernardino, San Bernardino, CA 92407

We present a new analysis of Spitzer observations of comet 29P/Schwassmann-Wachmann 1 taken on UT 2003 November 21, 23, and 24, similar to a previous investigation of the observations (Stansberry et al., 2004), but using the most recent Spitzer data pipeline products and intensive image processing techniques. Analysis of images from the IRAC 5.8 & 8.0 μμm bands and the MIPS 24.0 & 70.0 μμm bands resulted in photometry measurements of the nucleus after a suite of coma modeling and removal processes were implemented. SW1 was not identified in the 5.8 μμm image from the previous work so its incorporation into this analysis is entirely new. Using the Near Earth Asteroid Thermal Model ( Harris, 1998) resulted in a nucleus radius measurement of R = View the MathML source30.2-2.9+3.7 km and an infrared beaming parameter value of View the MathML sourceη=0.99-0.19+0.26. We also measured an infrared geometric albedo, p5.8p5.8 = 0.5 ±± 0.5. Extrapolating a 0.04 V-band albedo and using a normalized reflectivity gradient S′=14.94±1.09S′=14.94±1.09 [% (1000 Å)−1] ( Duffard et al., 2014) we recover an infrared albedo of p5.8p5.8 = 0.31 in the near infrared consistent with the value recovered from thermal modeling. The dust composition extracted from IRS spectra are very comet-like, containing mainly amorphous ferromagnesian silicates (but with a minority of crystalline silicates as well), water ice, and metal sulfides.

Reference
Schambeau CA, Fernández YR, Lisse CM, Samarasinha N, Woodney LM (2015) A New Analysis of Spitzer Observations of Comet 29P/Schwassmann-Wachmann 1. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.06.038]
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