The surface composition of Trojan asteroids: Constraints set by scattering theory

J. P. Emery, R. H. Brown

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


We present the results of spectral modeling of 17 Trojan asteroids. The surface composition of this group of objects (located just beyond the main belt, trapped in Jupiter's stable Lagrange points) remains uncertain due to an absence of diagnostic absorption features in their spectra. We quantitatively analyze spectra of these objects covering the range 0.3-4.0 μm using the formulation for scattering in a particulate medium developed by Hapke. Since the widest spectral range possible is desired to provide the most robust results, recently measured near-IR spectra are combined with previously published visible and near-IR data. These composite spectra are converted to and modeled in terms of geometric albedo to provide the additional constraint of the absolute brightness of the asteroids. It is important that this modeling is performed for a large number of objects, and results are derived based on trends among best-fit models. Under this rigorous examination, we find that it is unlikely that the red spectral slope is a result of organics on the surfaces, due mainly to the lack of absorptions in the L-band. Instead, anhydrous silicates adequately describe the spectral characteristics of this group of objects. A significant fraction of carbonaceous material is also likely present, but is not responsible for the red spectral slope in these models. Also, using these models, we estimate that these surfaces contain at most a few wt% of H2O ice and no more than 10-30 wt% of hydrated silicates.

Original languageEnglish (US)
Pages (from-to)131-152
Number of pages22
Issue number1
StatePublished - Jul 2004
Externally publishedYes


  • Asteroids, composition
  • Kuiper belt objects
  • Radiative transfer
  • Spectroscopy
  • Surface, asteroids

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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