Evidence of shallow subsurface ice at Tianwen-1 landing site

Abstract

Surface and shallow subsurface water ice has been identified in both polar and mid-to-high latitude regions of Mars. However, its distribution at low-to-mid latitudes remains under investigation. China’s first Mars mission, Tianwen-1, landed in southern Utopia Planitia, a region that shows geological evidence of an active hydrological past, making it an ideal site for the search for subsurface water ice. The Mars Rover Penetrating Radar (RoPeR) onboard the Zhurong Rover can reveal subsurface stratigraphy and material properties. It detected a ∼7 m thick layer of low-loss material sandwiched by two high-loss layers. The estimated loss tangent value (0.0030 ± 0.0018) and dielectric constant (∼3.86) are consistent with water ice, suggesting its possible presence at the depth of ${15}_{-5}^{+7}$ m. We conducted simulations exploring a range of scenarios that varied in loss materials, stone distribution, and density within the layer. The results indicate that a model incorporating dirty ice mixed with stones aligns most closely with the RoPeR observations. The presence of a shallow subsurface ice-bearing layer at low-to-mid latitudes would represent a valuable and readily accessible resource for future human exploration.