INVESTIGATION OF GROUNDWATER STAYING CONDITIONS IN THE AREA AROUND THE INSIGHT LANDING SITE BASED ON MARS REMOTE SENSING DATA

The high-precision CTX and THEMIS images along with HRSC-MOLA DEM elevation data of Mars are employed to analyze the morphological characteristics and distribution of faults in the area around the InSight landing site. It is found that wrinkle ridges and lobate scarps are the two most common types of faults in the study area. Wrinkle ridges mainly exhibit discontinuous linear landforms trending SSW and are concentrated in the northeastern part of the study area. Conversely, the lobate scarps, which are distributed throughout the study area, display a foliated unilateral linear morphology aligned parallel to the north-south bifurcation of Mars. Wrinkle ridges originated from compressive stress induced by cooling contraction and volcanism, while the lobate scarps were formed by a combination of cooling contraction stress and lithospheric bending in the southern highlands of the area.

The faults in the study area can be divided into three groups including giant faults with length great than 100km, secondary ones with length between 30-100km and small ones with length less than 30km. The elastic dislocation model was used to simulate the geometric parameters of faults, such as depth, dip and dislocation displacement etc. The results of simulation show that the depth of giant faults, the secondary faults and the small faults is about 28-33km, 17-23 km and 9-16 km respectively. The great dislocation displacements, which can reach hundreds of meters, of the faults reflect the process of substantial tectonic stress buildup and release.

In hydrogeology, the fissure distribution, determining the occurrence of groundwater, is influenced by the lithology, fissure density and scale of a fault. The vertical depth and horizontal extent of fissure distribution are large with the scale of a fault. Therefore, the deepest depth of fissure distribution is about 33km in the study area. From the analogy analysis of fissure distribution depth of the fault on Earth, three vertical fissure zones are divided, i.e. the cataclastic texture fissure zone inhabiting above 9 km, the block-fractured fissure zone inhabiting between 9 and 23 km, and the massive structure fissure zone inhabiting below 23 km. According to the formation pressure, the temperature and the fissure distribution beneath the studied area, it is calculated that the depth range for liquid groundwater is 7–23 km while ice inhabits above 7km.