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Visible Near-infrared Spectral Evolution of Irradiated Mixed Ices and Application to Kuiper Belt Objects and Jupiter Trojans

Poston, Michael J. and Mahjoub, Ahmed and Ehlmann, Bethany L. and Blacksberg, Jordana and Brown, Michael E. and Carlson, Robert W. and Eiler, John M. and Hand, Kevin P. and Hodyss, Robert and Wong, Ian (2018) Visible Near-infrared Spectral Evolution of Irradiated Mixed Ices and Application to Kuiper Belt Objects and Jupiter Trojans. Astrophysical Journal, 856 (2). Art. No. 124. ISSN 1538-4357. doi:10.3847/1538-4357/aab1f1.

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Understanding the history of Kuiper Belt Objects and Jupiter Trojans will help to constrain models of solar system formation and dynamical evolution. Laboratory simulations of a possible thermal and irradiation history of these bodies were conducted on ice mixtures while monitoring their spectral properties. These simulations tested the hypothesis that the presence or absence of sulfur explains the two distinct visible near-infrared spectral groups observed in each population and that Trojans and KBOs share a common formation location. Mixed ices consisting of water, methanol, and ammonia, in mixtures both with and without hydrogen sulfide, were deposited and irradiated with 10 keV electrons. Deposition and initial irradiation were performed at 50 K to simulate formation at 20 au in the early solar system, then heated to Trojan-like temperatures and irradiated further. Finally, irradiation was concluded and resulting samples were observed during heating to room temperature. Results indicated that the presence of sulfur resulted in steeper spectral slopes. Heating through the 140–200 K range decreased the slopes and total reflectance for both mixtures. In addition, absorption features at 410, 620, and 900 nm appeared under irradiation, but only in the H_2S-containing mixture. These features were lost with heating once irradiation was concluded. While the results reported here are consistent with the hypothesis, additional work is needed to address uncertainties and to simulate conditions not included in the present work.

Item Type:Article
Related URLs:
URLURL TypeDescription
Poston, Michael J.0000-0001-5113-1017
Mahjoub, Ahmed0000-0003-1229-5208
Ehlmann, Bethany L.0000-0002-2745-3240
Brown, Michael E.0000-0002-8255-0545
Hand, Kevin P.0000-0002-3225-9426
Hodyss, Robert0000-0002-6523-3660
Wong, Ian0000-0001-9665-8429
Additional Information:© 2018 The American Astronomical Society. Received 2017 September 8; revised 2018 January 11; accepted 2018 February 14; published 2018 March 30. This work has been supported by the W. M. Keck Institute for Space Studies (KISS). This work has been 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.
Group:Keck Institute for Space Studies, Astronomy Department
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
Subject Keywords:astrochemistry – Kuiper Belt: general – minor planets, asteroids: individual (Jupiter Trojans) – planets and satellites: surfaces – radiation: dynamics
Issue or Number:2
Record Number:CaltechAUTHORS:20181210-130709389
Persistent URL:
Official Citation:Michael J. Poston et al 2018 ApJ 856 124
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91644
Deposited By: Tony Diaz
Deposited On:10 Dec 2018 21:40
Last Modified:16 Nov 2021 03:43

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