After landing in the Utopia Planitia, Tianwen-1 formed the deepest landing crater on Mars, approximately 40 cm deep, exposing precious information about the mechanical properties of Martian soil. We established numerical models for the plume-surface interaction (PSI) and the crater formation based on Computational Fluid Dynamics (CFD) methods and the erosion model modified from Roberts’ Theory. Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties. The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth, with the cohesion having a greater impact. The influence of the nozzle height is not clear, as it interacts with the position of the Shock Diamond to jointly control the erosion process. Furthermore, we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics. Finally, we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site, with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25° to 41°.

中文翻译：

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“天问一号”着陆点的形成及着陆点附近火星土壤的力学特性


在乌托邦平原着陆后，“天问一号”形成了火星上最深的着陆坑，深约 40 厘米，揭示了有关火星土壤力学特性的宝贵信息。我们基于计算流体动力学 （CFD） 方法和从罗伯茨理论修改的侵蚀模型，建立了羽流-表面相互作用 （PSI） 和陨石坑形成的数值模型。对不同喷嘴高度和土壤力学特性的病例进行了比较研究。内聚力和内摩擦角的增加导致侵蚀速率和最大的陨石坑深度降低，内聚力的影响更大。喷嘴高度的影响尚不清楚，因为它与 Shock Diamond 的位置相互作用以共同控制腐蚀过程。此外，我们根据形态特征将着陆陨石坑的演变分为分散型和集中型侵蚀。最后，我们估计了天问一号着陆点附近火星土壤力学性质的上限，内聚力范围为 2612 至 2042 Pa，内摩擦角为 25° 至 41°。