PSI SEMINAR SERIES: 28 September 2004, 3:00pm
"Global distribution of hydrogen on Mars: implications for hydrated minerals and/or water ice."
The geographical distribution of water-equivalent-hydrogen (WEH) near the equator of Mars was compared with the topography and distribution of atmospheric water vapor to constrain possible recharge mechanisms of near-surface water (<1 m of the surface). Recharge through a subsurface conduit provided by an aquifer, although possible, seems less likely than recharge through the atmosphere. Although the spatial distribution of WEH does not correspond to the current distribution of water vapor in the atmosphere, several terrestrial analogs indicate that dynamics of atmospheric circulation during periods of higher obliquity prior to the present epoch can qualitatively account for the observed WEH distribution.
The stability of water ice, epsomite, and hexahydrite to loss of H2O molecules to the atmosphere at equatorial latitudes of Mars was also studied to determine their potential contributions to the measured abundance of water-equivalent hydrogen (WEH). Calculation of the relative humidity based on estimates of yearly averages of water-vapor pressures and temperatures at the Martian surface was used for this purpose. Water ice was found to be sufficiently unstable everywhere within 45 degrees of the equator that if the observed WEH is due to water ice, it requires a low-permeability cover layer near the surface to isolate the water ice below from the atmosphere above. In contrast, epsomite or hexahydrite may be stable in many near-equatorial locations where significant amounts of WEH are observed.
