NORTH-SOUTH ASYMMETRY OF SUBSURFACE WATER DISTRIBUTION ON MARS: IMPLICATION FROM A GLOBAL WATER CYCLE MODEL

摘要

The Gamma-Ray Spectrometer onboard Mars Odyssey recently detected in the near-surface soil of Martian polar region a high abundance of hydrogen, which is indicative of ground ice. In an effort to understand the observed global subsurface water distribution a global coupled atmosphere-subsurface water cycle model is developed. The simulation indicates that, regardless of the initial subsurface water distribution, the soil in the northern hemisphere becomes wetter compared to the southern hemisphere under the present climate. This hemispheric asymmetry is caued by a combination of higher ground ice sublimation rate in the south, stronger northward transport of atmospheric water and the presence of the northern residual polar cap as a major atmospheric water source. The presence of ground ice at the very top of the soil is unlikely because otherwise it would cause an excessive abundance of atmospheric water. Much of the water in the surficial soil at low and mid latitudes is inferred to be adsorbed water. Variability in thermal inertia, adsorptive capacity and topography (surface pressure) may contribute to the longitudinal spatial inhomogeneity of the soil water content.