Multi-wavelength JWST observations of (3200) Phaethon show a dehydrated object with an aqueously altered origin
Abstract
We present JWST observations of the near-Earth asteroid (3200) Phaethon using the Near-Infrared Camera (NIRCam), Near-Infrared Spectrograph (NIRSpec), and Mid-Infrared Instrument (MIRI) to further investigate the composition of Phaethon's surface. Our NIRSpec data confirms that Phaethon's surface is dehydrated, showing no evidence of hydrated minerals in the 3-m region. We estimate an upper limit on the hydrogen content in phyllosilicates of 0.06 wt%. Comparisons with laboratory spectra of carbonaceous chondrites suggest that Phaethon's surface composition is best matched by thermally metamorphosed samples of the CM chondrite Murchison (heated to 1000C), rather than CY meteorites as previous work suggested. We find no evidence of ongoing surface evolution due to recent perihelion passages. A comparison of the mid-infrared spectra of Phaethon and Bennu shows distinct spectral differences that are consistent with their different thermal histories. Our findings further refine our understanding of Phaethon's current surface composition and evolution and provide additional insights for the upcoming DESTINY+ mission.
Keywords
Cite
@article{arxiv.2505.00692,
title = {Multi-wavelength JWST observations of (3200) Phaethon show a dehydrated object with an aqueously altered origin},
author = {Cristina A. Thomas and Andrew S. Rivkin and Ian Wong and Matthew M. Knight and Sean E. Marshall and Christopher W. Haberle and Aidan Madden-Watson and Joshua P. Emery and Annika Gustafsson and Stefanie N. Milam and Heidi B. Hammel and Ellen S. Howell and Ronald J. Vervack},
journal= {arXiv preprint arXiv:2505.00692},
year = {2025}
}
Comments
17 pages, 11 figures, accepted Planetary Science Journal