Preliminary results on photometric properties of materials at the Sagan Memorial Station, Mars

Jeffrey R. Johnson, Randolph Kirk, Laurence A. Soderblom, Lisa Gaddis, Robert J. Reid, Daniel T. Britt, Peter Smith, Mark Lemmon, Nicolas Thomas, James F. Bell, Nathan T. Bridges, Robert Anderson, Ken E. Herkenhoff, Justin Maki, Scott Murchie, Andreas Dummel, Ralf Jaumann, Frank Trauthan, Gabriele Arnold

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


Reflectance measurements of selected rocks and soils over a wide range of illumination geometries obtained by the Imager for Mars Pathfinder (IMP) camera provide constraints on interpretations of the physical and mineralogical nature of geologic materials at the landing site. The data sets consist of (1) three small "photometric spot" subframed scenes, covering phase angles from 20° to 150°; (2) two image strips composed of three subframed images each, located along the antisunrise and antisunset lines (photometric equator), covering phase angles from ∼0° to 155°; and (3) full-image scenes of the rock "Yogi," covering phase angles from 48° to 100°. Phase functions extracted from calibrated data exhibit a dominantly backscattering photometric function, consistent with the results from the Viking lander cameras. However, forward scattering behavior does appear at phase angles >140°, particularly for the darker gray rock surfaces. Preliminary efforts using a Hapke scattering model are useful in comparing surface properties of different rock and soil types but are not well constrained, possibly due to the incomplete phase angle availability, uncertainties related to the photometric function of the calibration targets, and/or the competing effects of diffuse and direct lighting. Preliminary interpretations of the derived Hapke parameters suggest that (1) red rocks can be modeled as a mixture of gray rocks with a coating of bright and dark soil or dust, and (2) gray rocks have macroscopically smoother surfaces composed of microscopically homogeneous, clear materials with little internal scattering, which may imply a glass-like or varnished surface.

Original languageEnglish (US)
Article number98JE02247
Pages (from-to)8809-8830
Number of pages22
JournalJournal of Geophysical Research: Planets
Issue numberE4
StatePublished - Apr 25 1999
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography


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