The Planetary Science Journal (Jan 2023)

Near to Mid-infrared Spectroscopy of (65803) Didymos as Observed by JWST: Characterization Observations Supporting the Double Asteroid Redirection Test

  • Andrew S. Rivkin,
  • Cristina A. Thomas,
  • Ian Wong,
  • Benjamin Rozitis,
  • Julia de León,
  • Bryan Holler,
  • Stefanie N. Milam,
  • Ellen S. Howell,
  • Heidi B. Hammel,
  • Anicia Arredondo,
  • John R. Brucato,
  • Elena M. Epifani,
  • Simone Ieva,
  • Fiorangela La Forgia,
  • Michael P. Lucas,
  • Alice Lucchetti,
  • Maurizio Pajola,
  • Giovanni Poggiali,
  • Jessica N. Sunshine,
  • Josep M. Trigo-Rodríguez

DOI
https://doi.org/10.3847/PSJ/ad04d8
Journal volume & issue
Vol. 4, no. 11
p. 214

Abstract

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The Didymos binary asteroid was the target of the Double Asteroid Redirection Test (DART) mission, which intentionally impacted Dimorphos, the smaller member of the binary system. We used the Near-Infrared Spectrograph and Mid-Infrared Instrument instruments on JWST to measure the 0.6–5 and 5–20 μ m spectra of Didymos approximately two months after the DART impact. These observations confirm that Didymos belongs to the S asteroid class and is most consistent with LL chondrite composition, as was previously determined from its 0.6–2.5 μ m reflectance spectrum. Measurements at wavelengths >2.5 μ m show Didymos to have thermal properties typical for an S-complex asteroid of its size and to be lacking absorptions deeper than ∼2% due to OH or H _2 O. Didymos’ mid-infrared emissivity spectrum is within the range of what has been measured on S-complex asteroids observed with the Spitzer Space Telescope and is most consistent with emission from small (<25 μ m) surface particles. We conclude that the observed reflectance and physical properties make the Didymos system a good proxy for the type of ordinary chondrite asteroids that cross near-Earth space, and a good representative of likely future impactors.

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