Detection of a 2.85 μm Feature on Five Spinel-rich Asteroids from JWST

Abstract Ground-based observations of “Barbarian” L-type asteroids at 1–2.5 μ m indicate that their near-infrared spectra are dominated by the mineral spinel, which has been attributed to a high abundance of calcium-aluminum inclusions (CAIs)—the first solids to condense out of the protoplanetary di...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2024-05, Vol.967 (1), p.L11
Main Authors: Gomez Barrientos, Jonathan, de Kleer, Katherine, Ehlmann, Bethany L., Tissot, Francois L. H., Mueller, Jessica
Format: Article
Language:English
Subjects:
Absorption
Aluminum
Asteroid surfaces
Asteroids
Chondrites
Ground-based observation
Inclusions
Infrared spectra
Infrared spectroscopy
Jupiter
Minerals
Near infrared radiation
Planet formation
Protoplanetary disks
Reflectance
Solar system
Solar wind
Space telescopes
Space weathering
Spectroscopy
Spinel
Weathering
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Summary:Abstract Ground-based observations of “Barbarian” L-type asteroids at 1–2.5 μ m indicate that their near-infrared spectra are dominated by the mineral spinel, which has been attributed to a high abundance of calcium-aluminum inclusions (CAIs)—the first solids to condense out of the protoplanetary disk during the formation of the solar system. However, the spectral properties of these asteroids from 2.5–5 μ m, a wavelength region that covers signatures of hydrated minerals, water, and organics, have not yet been explored. Here, we present 2–5 μ m reflectance spectra of five spinel-rich asteroids obtained with the NIRSpec instrument on the James Webb Space Telescope. All five targets exhibit a ∼2.85 μ m absorption feature with a band depth of 3%–6% that appears correlated in strength with that of the 2 μ m spinel absorption feature. The shape and position of the 2.85 μ m feature are not a good match to the 2.7 μ m feature commonly seen in carbonaceous CM meteorites or C-type asteroids. The closest spectral matches are to the Moon and Vesta, suggesting commonalities in aqueous alteration across silicate bodies, infall of hydrated material, and/or space weathering by solar wind H implantation. Lab spectra of CO/CV chondrites, CAIs, as well as the minerals cronstedtite and spinel, also show a similar feature, providing clues into the origin of the 2.85 μ m feature.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ad4647