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A hypothesis for the color bimodality of Jupiter Trojans

Wong, Ian and Brown, Michael E. (2016) A hypothesis for the color bimodality of Jupiter Trojans. Astronomical Journal, 152 (4). Art. No. 90. ISSN 1538-3881. doi:10.3847/0004-6256/152/4/90.

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One of the most enigmatic and hitherto unexplained properties of Jupiter Trojans is their bimodal color distribution. This bimodality is indicative of two sub-populations within the Trojans, which have distinct size distributions. In this paper, we present a simple, plausible hypothesis for the origin and evolution of the two Trojan color sub-populations. In the framework of dynamical instability models of early solar system evolution, which suggest a common primordial progenitor population for both Trojans and Kuiper Belt objects, we use observational constraints to assert that the color bimodalities evident in both minor body populations developed within the primordial population prior to the onset of instability. We show that, beginning with an initial composition of rock and ices, location-dependent volatile loss through sublimation in this primordial population could have led to sharp changes in the surface composition with heliocentric distance. We propose that the depletion or retention of H_2S ice on the surface of these objects was the key factor in creating an initial color bimodality. Objects that retained H_2S on their surfaces developed characteristically redder colors upon irradiation than those that did not. After the bodies from the primordial population were scattered and emplaced into their current positions, they preserved this primordial color bimodality to the present day. We explore predictions of the volatile loss model—in particular, the effect of collisions within the Trojan population on the size distributions of the two sub-populations—and propose further experimental and observational tests of our hypothesis.

Item Type:Article
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URLURL TypeDescription Paper
Wong, Ian0000-0001-9665-8429
Brown, Michael E.0000-0002-8255-0545
Additional Information:© 2016 The American Astronomical Society. Received 2015 November 25; revised 2016 June 29; accepted 2016 July 12; published 2016 September 29. Discussions with the Keck Institute for Space Studies "In Situ Science and Instrumentation for Primitive Bodies" study group, including Bethany Ehlmann, Jordana Blacksberg, and John Eiler, were extremely valuable in the development of the model presented in this paper. We also thank Mario Melita for providing helpful comments and suggestions during the review process.
Subject Keywords:astrochemistry – minor planets, asteroids: general – planets and satellites: surfaces
Issue or Number:4
Record Number:CaltechAUTHORS:20161111-091911266
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Official Citation:Ian Wong and Michael E. Brown 2016 AJ 152 90
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71931
Deposited By: Tony Diaz
Deposited On:15 Nov 2016 01:42
Last Modified:11 Nov 2021 04:53

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