Exploring the subsurface structure and stratification of Mars advances our understanding of Martian geology, hydrological evolution and palaeoclimatic changes, and has been a main task for past and continuing Mars exploration missions1–10. Utopia Planitia, the smooth plains of volcanic and sedimentary strata that infilled the Utopia impact crater, has been a prime target for such exploration as it is inferred to have hosted an ancient ocean on Mars11–13. However, 45 years have passed since Viking-2 provided ground-based detection results. Here we report an in situ ground-penetrating radar survey of Martian subsurface structure in a southern marginal area of Utopia Planitia conducted by the Zhurong rover of the Tianwen-1 mission. A detailed subsurface image profile is constructed along the roughly 1,171 m traverse of the rover, showing an approximately 70-m-thick, multi-layered structure below a less than 10-m-thick regolith. Although alternative models deserve further scrutiny, the new radar image suggests the occurrence of episodic hydraulic flooding sedimentation that is interpreted to represent the basin infilling of Utopia Planitia during the Late Hesperian to Amazonian. While no direct evidence for the existence of liquid water was found within the radar detection depth range, we cannot rule out the presence of saline ice in the subsurface of the landing area.
Marsquakes excite seismic wavefield, allowing the Martian interior structures to be probed. However, the Martian seismic data recorded by InSight have a low signal-to-noise ratio, making the identification of marsquakes challenging. Here we use the Matched Filter technique and Benford’s Law to detect hitherto undetected events. Based on nine marsquake templates, we report 47 newly detected events, >90% of which are associated with the two high-quality events located beneath Cerberus Fossae. They occurred at all times of the Martian day, thus excluding the tidal modulation (e.g., Phobos) as their cause. We attribute the newly discovered, low-frequency, repetitive events to magma movement associated with volcanic activity in the upper mantle beneath Cerberus Fossae. The continuous seismicity suggests that Cerberus Fossae is seismically highly active and that the Martian mantle is mobile.
The South China Block (SCB), located in the southeastern part of the Eurasian continent, comprises the Yangtze Craton in the northwest and the Cathaysia Block in the southeast, as illustrated in Figure 1a. The two major blocks collided and amalgamated in the Neoproterozoic (1.1-1.0 Ga) along the Jiangnan orogen in the center through long-term plate tectonics and multiphase evolution (Faure et al., 2017;Mao et al., 2014;Zhang et al., 2013). The SCB is in a geologic environment with tectonic compression. In the north, the SCB is bounded by the Qinling-Dabie orogen resulting from collision with the North China Craton (NCC) in the Triassic (Cao et al., 2018;Enkin et al., 1992). In the west, the SCB is bordered by the Tibetan Plateau. The SCB is bounded by the Longmenshan Fault, separating it from the Songpan-Ganzi Block in the northwest.
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