Galileo imaging of SO2 frosts on Io

P. Geissler, A. McEwen, C. Phillips, D. Simonelli, R. M.C. Lopes, S. Douté

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Io's visible appearance changes dramatically with solar phase angle. The polar regions and some plume deposits near active volcanic centers become comparatively bright with increasing phase angle, while the equatorial band grows relatively dark. We suggest that the areas of Io that appear unusually bright at high phase are covered by thin frosts of SO2 that are transparent under normal illumination. A global disk-resolved photometric analysis indicates that the frosts exhibit more nearly isotropic or forwardscattering behavior and less opposition brightening than average Ionian materials. Comparison with Near-Infrared Mapping Spectrometer (NIMS) results suggests that these frosts have relatively strong 4.1 μm absorptions indicative of fine-grained SO2.

Original languageEnglish (US)
Article number2000JE001361
Pages (from-to)33253-33266
Number of pages14
JournalJournal of Geophysical Research E: Planets
Issue numberE12
StatePublished - Dec 25 2001

ASJC Scopus subject areas

  • Geophysics
  • Oceanography
  • Forestry
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Palaeontology


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