Highlights

• New data from the first 191 sols of Rover Penetrating Radar (RoPeR) CH2 reveals a heterogeneous material distribution in Martian regolith at the Tianwen-1 landing site, contrasting with the more uniform composition of airless bodies like the Moon.
• Initial radar results show varying loss tangent values across Martian regions, indicating diverse geological processes and compositions.
• The permittivity distribution map from RoPeR suggests novel insights into the Martian subsurface, revealing depth-related variations and potential for thicker regolith layers than previously assumed.

Summary

The Mars Rover Penetrating Radar, used in the Tianwen-1 mission, has provided valuable insights into the Martian surface, specifically the regolith, which has been found to have high lossy properties. This discovery by Ling Zhang and his team helps explain why subsurface reflectors were not detected in the landing region.

The study utilized Rover Penetrating Radar CH2 data to analyze Martian soil’s dielectric properties (how the regolith responds to electric fields). The findings revealed a heterogeneous distribution of materials across different areas and a gradual increase in permittivity (the material’s ability to pass an electric field) with depth. Researchers suggest a complex and varied subsurface structure. Additionally, indicators of water-ice and dust were found on the surface, although no distinct layered structures were detected beneath.

Measurements showed that within 5 meters of the landing site, the regolith’s permittivity is around 3.6±3.2..10, and the average loss tangent (indicating energy loss in the material) is 0.0174±0.00005533. These results highlight the diversity and relatively low weathering level of Martian soil. The study demonstrates that the regolith at this landing site is not predominantly water ice, and the high loss tangent suggests limitations in the radar’s ability to detect deeper subsurface features.

Furthermore, the study parallels previous research in this field, noting similarities with the loss tangent value in lunar regolith samples and their iron and titanium content. This comparison offers a broader perspective on Martian geology.

For those interested in further exploration of this research, the data and code used in the study are accessible online. This study provides critical insights into the Martian surface composition and enhances our understanding of the Red Planet’s geological processes.

L. Zhang, Y. Xu, R. Liu, R. Chen, R. Bugiolacchi, and R. Gao, “The Dielectric Properties of Martian Regolith at the Tianwen‐1 Landing Site,” Geophysical Research Letters, vol. 50, no. 13, p. e2022GL102207, Jul. 2023, doi: .