Surface Geology of Jupiter’s Trojan Asteroids

Marchi, S.; Bell, James F.; Bierhaus, B.; Spencer, J. R.

doi:10.1007/s11214-023-00985-9

Cited by 3 publications

(1 citation statement)

References 47 publications

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“…NASAʼs Lucy mission will be the first to study several Trojans up-close (Levison et al 2021). Two of the top-level science goals of Lucy include understanding these bodies' crater populations across a wide range of crater diameters (assuming the bodies are cratered; Marchi et al 2023). Understanding how well images taken with Lucyʼs highest resolution camera can be used to reproduce a known crater population is critical for understanding potential biases or limitations for imaging unknown crater populations.…”

Section: Introductionmentioning

confidence: 99%

Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L’LORRI): A Resolution Test for NASA's Lucy Mission

Robbins,

Beau Bierhaus,

Barnouin

et al. 2023

Planet. Sci. J.

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NASA's Lucy mission is designed to better understand the unique population of Trojan asteroids. Trojans were probably captured in Jupiter's L4 and L5 points early in the solar system's evolution and little altered since then. A critical investigation of Lucy is to use its highest-resolution camera, the Lucy Long Range Reconnaissance Imager (L’LORRI), to image Trojans’ surfaces to understand their geology and impact crater populations. Through crater statistics, the population of smaller bodies that produced those impacts, relative age differences across the bodies, and other comparative investigations between bodies can be studied. Mapping the crater population to the minimum diameters needed to achieve Lucy's objectives might require image subsampling and deconvolution (“processing”) to improve the spatial resolution, a process whereby multiple, slightly offset images are merged to create a single, better-sampled image and deconvolved with L’LORRI's point-spread function. Lucy's first Earth Gravity Assist (EGA1) provided an opportunity to test this process's accuracy using L’LORRI images of the Moon, whose crater population is well characterized and therefore provides ground-truth testing. Specifically, the lunar crater imaging by L’LORRI during EGA1 allowed us to compare crater statistics derived from raw and processed L’LORRI images with ground-truth statistics derived from higher-resolution lunar imaging from other missions. The results indicate the processing can improve impact crater statistics such that features can be identified and measured to ≈70% the diameter that they can otherwise be reliably mapped on native L’LORRI images. This test's results will be used in the observation designs for the Lucy flyby targets.

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Section: Introductionmentioning

confidence: 99%

Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L’LORRI): A Resolution Test for NASA's Lucy Mission

Robbins,

Beau Bierhaus,

Barnouin

et al. 2023

Planet. Sci. J.

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The Terminal Tracking Camera System on the NASA Lucy Trojan Asteroid Discovery Mission

Bell,

Zhao,

Cisneros

et al. 2023

Space Sci Rev

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The Terminal Tracking Camera system (TTCam) on the NASA Lucy Trojan asteroid Discovery mission consists of a pair of block redundant cameras and their associated electronics that are mounted on the spacecraft’s Instrument Pointing Platform and co-boresighted with the rest of the mission’s science payload instruments. The primary function of the TTCams is as a navigation system designed to provide an autonomous onboard late pre-encounter update of the location of each asteroid flyby target relative to the spacecraft. However, once the terminal tracking function is complete, the TTCam system will also provide 11.0°×8.2° field of view broadband (425-675 nm) images during the close approach phase of each asteroid flyby that will be used for scientific analyses like shape modeling and assessment of each target’s geology and topography. This paper provides an overview of the TTCam cameras and electronics, the science-focused requirements that the system is designed to meet, pointers to pre-flight calibration and in-flight calibration details for the cameras, as well as a high-level summary of the kinds of science that these images will enable for the mission.

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Surface Compositions of Trojan Asteroids

Emery,

Binzel,

Britt

et al. 2024

Space Sci Rev

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The Jupiter Trojan asteroids are a key population for understanding the chemical and dynamical evolution of the Solar System. Surface compositions of Trojans, in turn, provide crucial information for reconstructing their histories. NASA’s Lucy mission will soon complete the first spacecraft reconnaissance of this population. This review summarizes the current state of knowledge of Trojan surface compositions and looks ahead to expected advances in that knowledge from Lucy. Surface compositions of Trojans remain uncertain due to a relative lack of diagnostic absorption features, though dedicated observations have begun to provide some clues to compositions. Trojans have uniformly low albedos, with a population average of ∼5.3%, and red spectral slopes at ultraviolet, visible, and near-infrared wavelengths. A bimodality of spectral slopes has been detected and confirmed across all these wavelengths, and the ratio of “less-red” to “red” Trojans increases with decreasing size. A broad absorption at ∼3.1 μm in some less-red Trojans may indicate the presence of N-H bearing material. Mid-infrared emissivity spectra reveal the presence of fine-grained anhydrous silicates on the surfaces. The meteorite collection contains no identifiable analogs to Trojan asteroids. Among small body populations, some Main Belt asteroids, comets, irregular satellites, and Centaurs provide reasonable spectral matches, supporting some genetic relationships among some members of these groups. The cause of the observed spectral properties remains uncertain, but recent suggestions include a combination of volatile ice sublimation and space weathering or a combination of impact gardening and space weathering. The Lucy mission will provide detailed compositional analysis of (3548) Eurybates, (15094) Polymele, (11351) Leucus, (21900) Orus, and (617) Patroclus-Menoetius, a suite of targets that sample the diversity among the Trojan population along several dimensions. With these flybys, the Lucy mission is poised to resolve many of the outstanding questions regarding Trojan surface compositions, thereby revealing how the Trojans formed and evolved and providing a clearer view of Solar System history.

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Surface Geology of Jupiter’s Trojan Asteroids

Cited by 3 publications

References 47 publications

Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L’LORRI): A Resolution Test for NASA's Lucy Mission

Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L’LORRI): A Resolution Test for NASA's Lucy Mission

The Terminal Tracking Camera System on the NASA Lucy Trojan Asteroid Discovery Mission

Surface Compositions of Trojan Asteroids

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