Spectral heterogeneity on Phobos and Deimos: HiRISE observations and comparisons to Mars Pathfinder results

N. Thomas, R. Stelter, A. Ivanov, N. T. Bridges, K. E. Herkenhoff, A. S. McEwen

Research output: Contribution to journalArticle

27 Scopus citations


The High-Resolution Imaging Science Experiment (HiRISE) onboard Mars Reconnaissance Orbiter (MRO) has been used to observe Phobos and Deimos at spatial scales of around 6 and 20 m/px, respectively. HiRISE (McEwen et al.; JGR, 112, CiteID E05S02, DOI: 10.1029/2005JE002605, 2007) has provided, for the first time, high-resolution colour images of the surfaces of the Martian moons. When processed, by the production of colour ratio images for example, the data show considerable small-scale heterogeneity, which might be attributable to fresh impacts exposing different materials otherwise largely hidden by a homogenous regolith. The bluer material that is draped over the south-eastern rim of the largest crater on Phobos, Stickney, has been perforated by an impact to reveal redder material and must therefore be relatively thin. A fresh impact with dark crater rays has been identified. Previously identified mass-wasting features in Stickney and Limtoc craters stand out strongly in colour. The interior deposits in Stickney appear more inhomogeneous than previously suspected. Several other local colour variations are also evident. Deimos is more uniform in colour but does show some small-scale inhomogeneity. The bright streamers (Thomas et al.; Icarus, 123, 536556,1996) are relatively blue. One crater to the south-west of Voltaire and its surroundings appear quite strongly reddened with respect to the rest of the surface. The reddening of the surroundings may be the result of ejecta from this impact. The spectral gradients at optical wavelengths observed for both Phobos and Deimos are quantitatively in good agreement with those found by unresolved photometric observations made by the Imager for Mars Pathfinder (IMP; Thomas et al.; JGR, 104, 90559068, 1999). The spectral gradients of the blue and red units on Phobos bracket the results from IMP.

Original languageEnglish (US)
Pages (from-to)1281-1292
Number of pages12
JournalPlanetary and Space Science
Issue number13
StatePublished - Oct 1 2011


  • Deimos
  • Heterogeneity
  • Martian satellites
  • Phobos
  • Spectrophotometry

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'Spectral heterogeneity on Phobos and Deimos: HiRISE observations and comparisons to Mars Pathfinder results'. Together they form a unique fingerprint.

  • Cite this