C[O.sub.2] snow depth and subsurface water-ice abundance in the northern hemisphere of Mars. (Reports)

Observations of seasonal variations of neutron flux from the high-energy neutron detector (HEND) on Mars Odyssey combined with direct measurements of the thickness of condensed carbon dioxide by the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor show a latitudinal dependence of northern winter deposition of carbon dioxide. The observations are also consistent with a shallow substrate consisting of a layer with water ice overlain by a layer of drier soil The lower ice-rich layer contains between 50 and 75 weight % water, indicating that the shallow subsurface at northern polar latitudes on Mars is even more water rich than that in the south.
Mars undergoes seasons in which volatile species, carbon dioxide (C[O.sub.2]) and, to a much lesser extent, water are exchanged between the atmosphere and surface (1, 2). The winter deposition in [...]