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Production of Sulfur Allotropes in Electron Irradiated Jupiter Trojans Ice Analogs

Mahjoub, Ahmed and Poston, Michael J. and Blacksberg, Jordana and Eiler, John M. and Brown, Michael E. and Ehlmann, Bethany L. and Hodyss, Robert and Hand, Kevin P. and Carlson, Robert and Choukroun, Mathieu (2017) Production of Sulfur Allotropes in Electron Irradiated Jupiter Trojans Ice Analogs. Astrophysical Journal, 846 (2). Art. No. 148. ISSN 1538-4357. http://resolver.caltech.edu/CaltechAUTHORS:20170912-123557936

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Abstract

In this paper, we investigate sulfur chemistry in laboratory analogs of Jupiter Trojans and Kuiper Belt Objects (KBOs). Electron irradiation experiments of CH_3OH–NH_3–H_2O and H_2S–CH_3OH–NH_3–H_2O ices were conducted to better understand the chemical differences between primordial planetesimals inside and outside the sublimation line of H_2S. The main goal of this work is to test the chemical plausibility of the hypothesis correlating the color bimodality in Jupiter Trojans with sulfur chemistry in the incipient solar system. Temperature programmed desorption (TPD) of the irradiated mixtures allows the detection of small sulfur allotropes (S_3 and S_4) after the irradiation of H2S containing ice mixtures. These small, red polymers are metastable and could polymerize further under thermal processing and irradiation, producing larger sulfur polymers (mainly S_8) that are spectroscopically neutral at wavelengths above 500 nm. This transformation may affect the spectral reflectance of Jupiter Trojans in a different way compared to KBOs, thereby providing a useful framework for possibly differentiating and determining the formation and history of small bodies. Along with allotropes, we report the production of organo-sulfur molecules. Sulfur molecules produced in our experiment have been recently detected by Rosetta in the coma of 67P/Churyumov–Gerasimenko. The very weak absorption of sulfur polymers in the infrared range hampers their identification on Trojans and KBOs, but these allotropes strongly absorb light at UV and Visible wavelengths. This suggests that high signal-to-noise ratio UV–Vis spectra of these objects could provide new constraints on their presence.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/aa85e0DOIArticle
http://iopscience.iop.org/article/10.3847/1538-4357/aa85e0/metaPublisherArticle
ORCID:
AuthorORCID
Mahjoub, Ahmed0000-0003-1229-5208
Brown, Michael E.0000-0002-8255-0545
Ehlmann, Bethany L.0000-0002-2745-3240
Hodyss, Robert0000-0002-6523-3660
Hand, Kevin P.0000-0002-3225-9426
Additional Information:© 2017 The American Astronomical Society. Received 2017 May 13; revised 2017 August 1; accepted 2017 August 8; published 2017 September 12. This work was conducted at the Jet Propulsion Laboratory, Caltech, under a contract with the National Aeronautics and Space Administration (NASA) and at the Caltech Division of Geological and Planetary Sciences. This work was supported by the Keck Institute of Space Studies (KISS). We would like to thank the anonymous reviewer for pertinent comments that considerably improved the manuscript. U.S. Government sponsorship is acknowledged.
Group:Keck Institute for Space Studies
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Keck Institute of Space Studies (KISS)UNSPECIFIED
Subject Keywords:astrochemistry; Kuiper belt: general; methods: laboratory: molecular; molecular processes; techniques: imaging spectroscopy
Record Number:CaltechAUTHORS:20170912-123557936
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170912-123557936
Official Citation:Ahmed Mahjoub et al 2017 ApJ 846 148
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81360
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Sep 2017 19:56
Last Modified:12 Sep 2017 19:56

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