Dielectric properties of Asteroid Vesta's surface as constrained by Dawn VIR observations

Elizabeth M. Palmer, Essam Heggy, Maria T. Capria, Federico Tosi

Research output: Contribution to journalArticle

4 Citations (Scopus)


Earth and orbital-based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, one can constrain their surface textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith-employing an analogy to the dielectric properties of lunar soil, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the real part of the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.3 to 2.5 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diurnal temperature, ranging from 6×10-3 to 8×10-3. We estimate the surface porosity to be ~55% in the upper meter of the regolith, as derived from VIR observations. This is ~12% higher than previous estimation of porosity derived from previous Earth-based X- and S-band radar observation. We suggest that the radar backscattering properties of asteroid Vesta will be mainly driven by the changes in surface roughness rather than potential dielectric variations in the upper regolith in the X- and S-band.

Original languageEnglish
Pages (from-to)93-101
Number of pages9
Publication statusPublished - 1 Dec 2015
Externally publishedYes



  • Asteroid Vesta
  • Asteroids, surfaces
  • Radar observations

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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