Shulou(Shulou.com)12/24 Report--

CTOnews.com, November 30, according to the Voice of the Chinese Academy of Sciences, Chinese scientists believe that there are 16 ancient polygonal landforms 35 meters below the surface of Mars by analyzing the frequency spectrum of the low-frequency radar data of "Zhurong".

The Zhurong rover landed in the southern part of the Martian utopian plain. The low-frequency radar (Rover Penetrating Radar,RoPeR) carried by the Zurong discovered the vertical hierarchical structure of the landing area and revealed several fire surface transformation events related to water activities, which provided an important basis for the analysis of Martian geological evolution, environment and climate change (Li et al., 2022).

This study was conducted by the Mars Radar team of the Institute of Geology and Geophysics of the Chinese Academy of Sciences in conjunction with the Institute of Aerospace Information Innovation of the Chinese Academy of Sciences, Chengdu University of Technology, the Institute of Geochemistry of the Chinese Academy of Sciences, the Center of Excellence and Innovation of Comparative Planetology of the Chinese Academy of Sciences, the National Center of Space Science of the Chinese Academy of Sciences, the University of the Chinese Academy of Sciences and Hehai University.

This study suggests that underground polygons may have been generated by early Martian freeze-thaw cycles (figure 3). The study shows that there are significant differences in structures above and below the depth of ~ 35m, indicating that significant changes have taken place in the water activity and / or thermal conditions of Mars in the late Western to early Amazon period. this means that a strong paleoclimate change occurred in the middle and low latitudes (~ 25 °N), or related to the change of the inclination of the ancient Martian orbit.

▲ figure 1.   "Zhurong" Mars rover landing site and utopian plain polygonal landform: (a) Utopian plain topographic map, the cross shows the "Zhu Rong" Mars rover, "Viking 2" rover and "perseverance" Mars rover landing sites; the black isoline is the-4 km elevation; the area of the four polygonal landforms (figure 1c-1f) is marked with white squares. (B) the route of the "Zhu Rong" Mars rover from Sol 11 to Sol 113; the green line segment represents the wedge of the underground polygon identified in figure 2 (P1-P16), and the purple line segment represents the interior of the polygon; and (c Merf) four representative polygonal landforms in the utopian plain are located as shown in figure 1A.

▲ figure 2. Underground polygonal landforms revealed by time-varying average frequencies of   low-frequency radar data: (a) time-varying average frequency of low-frequency radar data after noise suppression; green line segment (P1-P16) represents wedges between underground polygons; (b) superposition amplitude spectrum (black curve) obtained by accumulating time-varying average frequencies along the depths of 35-65 m (top and bottom of the observed polygon) (C) A plane map of the underground polygon landform is explored, with arrows indicating the direction of the rover, purple representing the interior of the polygon, and green representing the wedge between the polygons; (d) a schematic diagram of the definition of the geometric characteristics of the polygon; (e) a histogram of the diameter of the polygon identified in figure b; (f) a comparative analysis of the diameters of the polygons on Earth and Mars.

▲ figure 3. Schematic diagram of polygonal geomorphology formation in the landing area of   "Zhurong": (a) surface thermal shrinkage cracking; (b) fissures filled with water / ice and / or soil materials, resulting in three types of polygonal landforms (ice wedges, composite wedges and sand wedge polygons); (c) polygonal landforms stopped developing during the late Western-early Amazon period; and (d) polygonal landforms were covered at a later stage. CTOnews.com attached the reference address of the paper: Zhang, L.A., Li, C., Zhang, J. et al. Buried palaeo-polygonal terrain detected underneath Utopia Planitia on Mars by the Zhurong radar. Nat Astron (2023). Https://doi.org/10.1038/s41550-023-02117-3

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