Solar System Research

, Volume 39, Issue 1, pp 1–21 | Cite as

The Medusae Fossae-Elysium region, Mars: geologic characteristics of the depression of epithermal-neutron flux based on HEND measurements onboard the Mars Odyssey spacecraft

  • M. A. Ivanov
  • A. S. Kozyrev
  • M. L. Litvak
  • I. G. Mitrofanov


We studied the geological structure and characteristics of fluxes of fast and epithermal neutrons from the area of Mars within 50°S–50° N and 120°–240° W, the Medusae Fossae-Elysium region. The study area does not show any anomalies in the energy spectrum of fast neutrons, indicating that a thin (10–20 cm) subsurface layer in the equatorial region is characterized by quite a uniform distribution of hydrogen-containing phases. At the same time, the studied region is characterized by a distinct depression in the epithermal-neutron flux, which is outlined by a 0.150–0.170 counts/s contour line and does not show any seasonal changes in its shape, depth, and latitudinal position. This suggests that the depression is not associated with the short-term (seasonal) variations of the temperature regime and that it represents an aggregation of hydrogen-containing phases with longer lifetimes. The position of the epithermal-neutron-flux depression does not correlate with regional geology, and none of the geological units can be responsible for its appearance. To a rather greater degree, the flux of epithermal neutrons correlates with the amount of dust material on the surface. This indicates that the dust material presumably played a major role in the formation of the neutron-flux depression within the Medusae Fossae-Elysium region. The depression of the epithermal-neutron flux presumably has a polygenic nature. It can be related both to the primary accumulation of water-bearing material and to the later blowing of this material by wind and transportation of the dust fraction with its simultaneous enrichment in hydrogen-containing phases (most likely, in water-bearing minerals).


Depression Fast Neutron Subsurface Layer Geological Unit Regional Geology 
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Copyright information

© MAIK “Nauka/Interperiodica” 2005

Authors and Affiliations

  • M. A. Ivanov
    • 1
  • A. S. Kozyrev
    • 2
  • M. L. Litvak
    • 2
  • I. G. Mitrofanov
    • 2
  1. 1.Vernadsky Institute of Geochemistry and Analytical ChemistryRussian Academy of SciencesMoscowRussia
  2. 2.Space Research InstituteRussian Academy of SciencesMoscowRussia

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