Geochemistry of Martian soil and bedrock in mantled and less mantled terrains with gamma ray data from Mars Odyssey

Horton E. Newsom, Larry S. Crumpler, Robert C. Reedy, Michael T. Petersen, Gary C. Newsom, Larry G. Evans, G. Jeffrey Taylor, John M. Keller, Daniel M. Janes, William V. Boynton, Kris E. Kerry, Suniti Karunatillake

Research output: Contribution to journalArticle

23 Scopus citations


Surficial materials, including soil and dust, are abundant in the upper tens of centimeters of the Martian surface sensed by the Mars Odyssey Gamma Ray Spectrometer (GRS). Seven large areas (14% of the Martian surface) that represent possible compositional end-members were selected, including three regions heavily mantled with surficial materials. The selection process included mapping the ratio of exposed rocky terrain to surficial materials using high-resolution imagery. GRS data for H, Cl, Fe, Si, K, and Th were obtained for each area. The areas are chemically homogeneous within each area, given the spatial resolution and analytical uncertainty of the GRS data. However, substantial chemical differences exist among the areas, including the different mantled terrains, contrary to earlier assumptions that surficial materials are globally homogeneous due to aeolian mixing. The observed chemical differences among the areas may be due to variations in the protolith compositions, extent of alteration of the protolith regions, or post soil formation processes. The abundances of Cl, K, and Th in rockier (but still soil-rich) areas such as Syrtis Major Planum can be explained by mixing between a soil with higher concentrations of Cl, K, and Th, similar to the abundances in the mantled terrains (and some of the landing sites), and crustal rocks containing lower abundances of these elements, similar to Martian meteorites.

Original languageEnglish (US)
Article numberE03S12
JournalJournal of Geophysical Research: Space Physics
Issue number3
Publication statusPublished - Mar 20 2007


ASJC Scopus subject areas

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

Cite this

Newsom, H. E., Crumpler, L. S., Reedy, R. C., Petersen, M. T., Newsom, G. C., Evans, L. G., ... Karunatillake, S. (2007). Geochemistry of Martian soil and bedrock in mantled and less mantled terrains with gamma ray data from Mars Odyssey. Journal of Geophysical Research: Space Physics, 112(3), [E03S12].