JWST near-infrared spectroscopy of the Lucy Jupiter Trojan flyby targets: Evidence for OH absorption, aliphatic organics, and CO${}_2$

Abstract

We present observations obtained with the Near Infrared Spectrograph on JWST of the five Jupiter Trojans that will be visited by the Lucy spacecraft -- the Patroclus-Menoetius binary, Eurybates, Orus, Leucus, and Polymele. The measured 1.7-5.3 $\mu$m reflectance spectra, which provide increased wavelength coverage, spatial resolution, and signal-to-noise ratio over previous ground-based spectroscopy, reveal several distinct absorption features. We detect a broad OH band centered at 3 $\mu$m that is most prominent on the less-red objects Eurybates, Patroclus-Menoetius, and Polymele. An additional absorption feature at 3.3-3.6 $\mu$m, indicative of aliphatic organics, is systematically deeper on the red objects Orus and Leucus. The collisional fragment Eurybates is unique in displaying an absorption band at 4.25 $\mu$m that we attribute to bound or trapped CO${}_2$. Comparisons with other solar system small bodies reveal broad similarities in the 2.7-3.6 $\mu$m bands with analogous features on Centaurs, Kuiper belt objects (KBOs), and the active asteroid 238P. In the context of recent solar system evolution models, which posit that the Trojans initially formed in the outer solar system, the significant attenuation of the 2.7-3.6 $\mu$m absorption features on Trojans relative to KBOs may be the result of secondary thermal processing of the Trojans' surfaces at the higher temperatures of the Jupiter region. The CO${}_2$ band manifested on the surface of Eurybates suggests that CO${}_2$ may be a major constituent in the bulk composition of Trojans, but resides in the subsurface or deeper interior and is largely obscured by refractory material that formed from the thermophysical processes that were activated during their inward migration.

Published in PSJ. 13 pages, 6 figures

References in corpus (29)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope I. Overview of the instrument and its capabilities
• Origin of the Structure of the Kuiper Belt during a Dynamical Instability in the Orbits of Uranus and Neptune
• The Active Centaurs
• "TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations
• In-orbit Performance of the Near-Infrared Spectrograph NIRSpec on the James Webb Space Telescope
• Ammonium salts are a reservoir of nitrogen on a cometary nucleus and possibly on some asteroids
• Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt Object
• Water Ice and Dust in the Innermost Coma of Comet 103P/Hartley 2
• Visible spectroscopic and photometric survey of Jupiter Trojans: final results on dynamical families
• The Properties of Jovian Trojan Asteroids Listed in SDSS Moving Object Catalog 3
• The distribution of CO${}_2$ on Europa indicates an internal source of carbon
• A hypothesis for the color bimodality of Jupiter Trojans
• Taxonomy of asteroid families among the Jupiter Trojans: Comparison between spectroscopic data and the Sloan Digital Sky Survey colors
• Infrared detection of aliphatic organics on a cometary nucleus
• The bimodal color distribution of small Kuiper Belt objects
• The differing magnitude distributions of the two Jupiter Trojan color populations
• Irradiation dose affects the composition of organic refractory materials in space: Results from laboratory analogues
• The 3 $\mu$m Spectrum of Jupiter's Irregular Satellite Himalia
• Compositional Constraints for Lucy Mission Trojan Asteroids via Near-Infrared Spectroscopy
• Observational Constraints on Water Sublimation from 24 Themis and 1 Ceres
• Photometry of active Centaurs: Colors of dormant active Centaur nuclei
• Implications for the collisional strength of Jupiter Trojans from the Eurybates family
• Hubble Ultraviolet Spectroscopy of Jupiter Trojans
• The Upcoming Mutual Event Season for the Patroclus - Menoetius Trojan Binary
• Multiband photometry of a Patroclus-Menoetius mutual event: Constraints on surface heterogeneity
• Photometric Confirmation and Characterization of the Ennomos Collisional Family in the Jupiter Trojans
• A Crater Chronology for the Jupiter's Asteroids

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