Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar

The Martian subsurface structure archives the magmatic activity, sedimentary processes, and meteorite impact history of Mars, making it a promising region for investigating the geological evolution and ancient water activities of the planet. On 15 May 2021, China’s first Mars mission, Tianwen-1, successfully landed on the south of Utopia Planitia and released the Zhurong rover to in-situ detect the subsurface structure with the equipped ground penetrating radar (Rover Penetrating Radar, RoPeR). Using the low-frequency channel radar data recorded during the first 113 Sols, a high-precision radar imaging result of depths exceeding 80 meters beneath the surface was obtained, following effective random noise attenuation and velocity inversion. Beneath the Martian regolith layer, which is several meters thick, two fining-upward sedimentary sequences were identified at depths of about 10–30 meters and 30–80 meters. Further analysis using dielectric permittivity inversion yielded insights into the strata’s physical properties, indicating that southern Utopia Planitia underwent multiple water-related resurfacing events since the Late Hesperian period (3.5–3.2 billion years ago). Hydrological processes might have persisted until the middle and late Amazonian period (around 1.6 billion years ago). No evidence of liquid water was found within the upper 80 meters of the subsurface in this region, although the presence of saline ice cannot be ruled out.