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JWST observations of the 1.7-5.3 μm spectra of the Lucy Mission Jupiter Trojan targets

Presentation #411.09 in the session Asteroids: Main Belt (Poster)

Published onOct 23, 2023
JWST observations of the 1.7-5.3 μm spectra of the Lucy Mission Jupiter Trojan targets

The Lucy mission will perform the first ever exploration of the Jupiter Trojan asteroids, small bodies in two vast swarms trapped at the Lagrange points leading and trailing the orbit of Jupiter. At an identical orbital distance as Jupiter, the Trojan asteroids are balanced precisely on the edge between the inner and outer solar system and hold important clues to the evolution of the entire planetary system. In the classical picture of solar system evolution, the Trojans formed in place or on the outer edge of the asteroid belt and bear a genetic connection to the inner solar system. The newer dynamical instabilty hypotheses, in contrast, posit a drastically different scenario in which the Trojans originated in a vast primordial disk of icy planetesimals beyond the giant planets and were later scattered inward and captured into resonance during a chaotic restructuring of the giant planets’ orbits . In this hypothesis, the Trojans formed alongside the outer solar system small bodies, including the present-day Kuiper belt objects. Direct comparisons of the Trojans’ observable properties with those of other small body populations promise to resolve this fundamental open question in our understanding of the early dynamical evolution of the solar system.

Lucy will fly by five distinct targets spanning the full range of known Trojan types, from the rare C-type to the more common P- and D-types, and from large intact bodies to the fragment of a known collisional family. The Lucy mission will provide a unique opportunity to examine the diversity of Trojans up close. Observations with JWST serve as a critical complement to the science that Lucy will enable.

Here, we present 1.7-5.3 μm JWST disk-integrated spectra of the 5 Lucy target systems. These spectra are at higher spectral resolution and extend to longer wavelengths than the LEISA spectrometer on Lucy. The Lucy spectroscopic observation, in contrast, will be spatially resolved, allowing the search for distinct exposures of minor components. The 5 targets show a range shallow but robust spectral features, including a 3 μm absorption, features associated with organic materials, a 3.8 μm feature possibly associated with carbonates, and a feature at 4.26 μm similar to the trapped CO2 seen on icy satellites. We will discuss the implications of these features for the surface composition of these targets and how they inform the upcoming observations from Lucy.

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