Detection of a 2.85 micrometer Feature on 5 Spinel-rich Asteroids from JWST

• Published in: arXiv.org
• Main Authors: Jonathan Gomez Barrientos, de Kleer, Katherine, Ehlmann, Bethany L, Tissot, Francois L H, Mueller, Jessica
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 20.05.2024
• Subjects: Absorption; Asteroids; Chondrites; Ground-based observation; Inclusions; Infrared spectra; Jupiter; Minerals; Near infrared radiation; Physics - Earth and Planetary Astrophysics; Physics - Geophysics; Planet formation; Protoplanetary disks; Solar wind; Space telescopes; Space weathering; Spinel
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2405.12281

Ground-based observations of `Barbarian' L-type asteroids at 1 to 2.5-\(\mu\)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 to 5-\(\mu\)m, a wavelength region that covers signatures of hydrated minerals, water, and organics, have not yet been explored. Here, we present 2 to 5-\(\mu\)m reflectance spectra of five spinel-rich asteroids obtained with the NIRSpec instrument on the James Webb Space Telescope. All five targets exhibit a \(\sim\) 2.85-\(\mu\)m absorption feature with a band depth of 3-6\(\%\) that appears correlated in strength with that of the 2-\(\mu\)m spinel absorption feature. The shape and position of the 2.85-\(\mu\)m feature are not a good match to the 2.7-\(\mu\)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-\(\mu\)m feature.