Radar Sounder Survey of Seasonal and Diurnal Water Flows on Mars Surface: Simulation and SHARAD Observation

The high-frequency radar sounder is an effective tool for Mars surface/subsurface exploration. To survey the seasonal water flows on the Mars surface, which have been recently reported, the radar sounder echoes from dry surface or water flowing surface are numerically simulated, respectively. The cratered rough surface is first divided into triangulated meshes, and numerical range echoes of the radar sounder from rough surface are calculated using a physical optics approach. Simulation results show that the radar echoes from water flowing surface with high dielectric constant are significantly enhanced, as signatures of seasonal and diurnal variation of surface dielectric properties during the daytime of warm season. To validate these simulation results, two orbits of SHAllow RADar (SHARAD) data, one on daytime of early autumn and another one at night of winter, passing over the Palikir Crater region are specifically chosen. It had been reported that there might be canals with flowing liquid saline water during daytime of warm seasons. Comparison of seasonal and diurnal SHARAD data on the same location can illustrate the enhanced radar echoes likely due to the appearance of surface brines. Quantitative inversion of the surface dielectric constant in warm seasons is also attempted. Numerical simulation of parameterized surface model and SHARAD data demonstrate that the radar sounder exploration is a good technology for the global survey of possible water flowing on the Mars surface during the daytime of warm seasons.