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Electron Irradiation and Thermal Processing of Mixed-ices of Potential Relevance to Jupiter Trojan Asteroids

Mahjoub, Ahmed and Poston, Michael J. and Hand, Kevin P. and Brown, Michael E. and Hodyss, Robert and Blacksberg, Jordana and Eiler, John M. and Carlson, Robert W. and Ehlmann, Bethany L. and Choukroun, Mathieu (2016) Electron Irradiation and Thermal Processing of Mixed-ices of Potential Relevance to Jupiter Trojan Asteroids. Astrophysical Journal, 820 (2). Art. No. 141. ISSN 0004-637X. doi:10.3847/0004-637X/820/2/141.

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In this work we explore the chemistry that occurs during the irradiation of ice mixtures on planetary surfaces, with the goal of linking the presence of specific chemical compounds to their formation locations in the solar system and subsequent processing by later migration inward. We focus on the outer solar system and the chemical differences for ice mixtures inside and outside the stability line for H_2S. We perform a set of experiments to explore the hypothesis advanced by Wong & Brown that links the color bimodality in Jupiter's Trojans to the presence of H_2S in the surface of their precursors. Non-thermal (10 keV electron irradiation) and thermally driven chemistry of CH_3OH–NH_3–H_2O ("without H_2S") and H_2S–CH_3OH–NH_3–H_2O ("with H_2S") ices were examined. Mid-IR analyses of ice and mass spectrometry monitoring of the volatiles released during heating show a rich chemistry in both of the ice mixtures. The "with H_2S" mixture experiment shows a rapid consumption of H_2S molecules and production of OCS molecules after a few hours of irradiation. The heating of the irradiated "with H_2S" mixture to temperatures above 120 K leads to the appearance of new infrared bands that we provisionally assign to SO_2 and CS. We show that radiolysis products are stable under the temperature and irradiation conditions of Jupiter Trojan asteroids. This makes them suitable target molecules for potential future missions as well as telescope observations with a high signal-to-noise ratio. We also suggest the consideration of sulfur chemistry in the theoretical modeling aimed at understanding the chemical composition of Trojans and KOBs.

Item Type:Article
Related URLs:
URLURL TypeDescription
Mahjoub, Ahmed0000-0003-1229-5208
Poston, Michael J.0000-0001-5113-1017
Hand, Kevin P.0000-0002-3225-9426
Brown, Michael E.0000-0002-8255-0545
Hodyss, Robert0000-0002-6523-3660
Ehlmann, Bethany L.0000-0002-2745-3240
Additional Information:© 2016 The American Astronomical Society. Received 2015 November 23; accepted 2016 February 16; published 2016 March 30. 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). Government sponsorship is acknowledged.
Group:Keck Institute for Space Studies, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Keck Institute of Space Studies (KISS)UNSPECIFIED
Subject Keywords:astrochemistry; Kuiper Belt: general; methods: laboratory: molecular; molecular processes; techniques: spectroscopic
Issue or Number:2
Record Number:CaltechAUTHORS:20160510-105413588
Persistent URL:
Official Citation:Ahmed Mahjoub et al 2016 ApJ 820 141
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66898
Deposited By: Ruth Sustaita
Deposited On:10 May 2016 19:01
Last Modified:11 Nov 2021 00:23

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