Investigation of Radar Subsurface Sounding through Seasonal Cycles Collected by Mars Shallow Radar (SHARAD) in the South Polar Area

Abstract

Using an orbital-based ground-penetrating radar - SHARAD proves to be an effective method for imaging the Martian surface and subsurface layering at the south polar layered deposit. This investigation focuses on examining whether seasonal variation of CO2 thickness on the surface caused by accumulation during winter and sublimation during summer could be observed for the first time by analyzing SHARAD data. Travel time and amplitude analysis between the Martian surface reflection and a reference reflection in the subsurface were conducted on multiple orbital tracks corresponding to varying seasons. Results from the travel time analysis along all four cross-lines show that the average change in CO2 frost thickness ranged from 6.80 m to 9.58 m assuming a medium dielectric constant between 2.12 and 2.77. The CO2 thickness reaches its maximum during winter and minimum during summer likely because of the CO2 frost accumulation and retreat, respectively. This observation agrees with other studies. However, the magnitude of change in CO2 thickness estimated in this study is greater than values reported previously. This difference is attributed to the different locations of the Martian polar region examined in the various studies. Amplitude analysis does not show any relationship to seasonal variations on the Martian surface.