The Dielectric Properties of Martian Regolith at the Tianwen‐1 Landing Site

Abstract

On Mars, compared to an airless body such as the Moon, the weathering layer ("regolith", a general term for the layer of fragmental and unconsolidated rock material, whether residual or transported and of highly varied character, that nearly everywhere forms the surface of the land and overlies or covers bedrock) underwent complicated geological processes in addition to weaker impact and space weathering modifications. A fuller understanding of the stratigraphy and properties of the martian regolith would unravel the local evolution history and help address key geological questions, including the potentiality of liquid water on the surface or near-surface (Christensen et al., 2008). The characterization of the dielectric properties of the weathering layer represents a key target of this quest.Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) and the Mars Express orbiter and the Shallow Radar (SHARAD) have revealed significant features beneath the surface and also obtained the subsurface dielectric characteristics to constrain the composition of the materials. A 3-5 MHz global permittivity map has been derived from MARSIS data, providing insights into the physical properties within the first ∼60-80 m below the surface (Mouginot et al., 2012). The permittivity of the first few meters of the martian regolith calculated by the SHARAD surface echoes shows a significant correspondence with the geological dichotomy: high permittivity (7-10) on the highland side but lower (3-7) on the lowland side (Castaldo et al., 2017). The loss tangent value inferred from radar data has also been used to infer the possible presence of water ice (e.g., Campbell et al., 2021;Campbell & Morgan, 2018). Though the MARSIS and the SHARAD can detect the reflections on the surface and subsurface down to a depth of hundreds of meters, they have a limited ability to discriminate the presence of internal structures in the shallow subsurface regolith.

Mars Rover Penetrating Radar Modeling and Interpretation Considering Linear Frequency Modulation Source and Tilted Antenna

“…Furthermore, two tilted interfaces are constructed at the model bottom, with electrical parameters of r = 9.00 and σ = 2.61 × 10 −4 S/m. The recent research has indicated that the loss tangent value of Martian regolith at the Tianwen-1 landing site is 0.0174 +0.0053 −0.0053 [29]. The loss tangent value of 0.0174 is used to evaluate the conductivity of σ = 5.246 × 10 −5 .…”

Surface Permittivity Estimation of Southern Utopia Planitia by High-Frequency RoPeR in Tianwen-1 Mars Exploration

“…Due to the special nature of planetary exploration, the hyperbolic method is widely used in the relative permittivity estimation of the rover mounted GPR data. Researchers have utilised this method to calculate relative permittivity for the Martian Rover radar data, including "RIMFAX", the GPR carried by the Perseverance Rover [21]- [23] and the RoPeR mounted on the Zhurong Rover [24] [25].…”