Comparative Mid-Infrared Spectroscopy of Dark, Primitive Asteroids: Does Shared Taxonomic Class Indicate Shared Silicate Composition?

Abstract

Primitive asteroids with low albedos and red slopes in the visible and near infrared (VNIR) are found in both the Main Belt and the Jupiter Trojan clouds. In order to determine whether the VNIR spectral similarities of primitive Main Belt asteroids and Jupiter Trojans are reflective of a true compositional similarity, we compare the mid-infrared silicate emission features of Main Belt and Jupiter Trojan asteroids. Using archival data from the Spitzer Space Telescope's IRS spectrograph and observations from the Stratospheric Observatory for Infrared Astronomy's (SOFIA) FORCAST instrument, we analyze the 5-40 micron spectra of thirteen primitive Main Belt asteroids and compare them to those of Jupiter Trojans in the literature. We find that while many primitive asteroids in the Main Belt resemble their Trojan counterparts with strong spectral signatures of olivine-rich high-porosity silicate regoliths, we identify (368) Haidea as a spectrally distinctive asteroid that lacks strong evidence of olivine in its MIR spectrum. Differences in silicate compositions among D-type asteroids imply a diversity of origins for primitive asteroids.

22 Pages, 9 figures, draft version accepted for publication in PSJ

References in corpus (5)

• The consequences of planetary migration on the minor bodies of the early Solar System
• Mid-infrared spectra of comet nuclei
• Discovery of two TNO-like bodies in the asteroid belt
• Reflection, emission, and polarization properties of surfaces made of hyperfine grains, and implications for the nature of primitive small bodies
• Compositional Constraints for Lucy Mission Trojan Asteroids via Near-Infrared Spectroscopy

Cited by in corpus (1)

• Primitive asteroids in the main belt, Cybele, and Hilda populations from Gaia DR3