Arcadia Planitia, a region in the northern midlatitudes of Mars, displays an uncommonly high abundance of simple craters with a concentric morphology, which is indicative of layering beneath the surface. Radar measurements suggest that the near surface layers could be made of excess water ice. In this study, we select two of these impact structures of similar size (D_c ~ 500 m), model their formation through iSALE shock physics code, and investigate the dependence of the final crater morphology on the material model parameters (cohesion and friction coefficient). Our parameter study shows that the intact and damaged cohesions of the nonporous ice play a fundamental role to obtain a good fit between our models and the topographic profiles taken from the digital terrain models in terms of crater diameter, crater wall inclination, and depth and size of the upper terrace. The central pit shape is instead controlled by the damaged friction coefficient of the basaltic crust, but it is mainly affected by projectile density and speed. Our results confirm that two layers of relatively pure water ice, each with different rheology and porosity, can explain the unique double‐terraced morphology of impact craters in Arcadia Planitia. The low values of cohesion we find for the ice might point to snowfall as emplacement mechanism in the region. The different thicknesses of the ice layers in the two crater areas seem to suggest variations in ice deposition and/or evolution history across Arcadia Planitia.

中文翻译：

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简单阶梯状火山口形成模型揭示火星冰

火星中北纬度地区的Arcadia Planitia显示出异常丰富的具有同心形态的简单陨石坑，这表明在地表以下分层。雷达测量表明，近地表层可能由过量的水冰制成。在这项研究中，我们选择了两个大小相似的冲击结构（D _c 〜500 m），通过iSALE冲击物理代码对它们的形成进行建模，并研究最终的坑形形态对材料模型参数（内聚力和摩擦系数）的依赖性。我们的参数研究表明，无孔冰的完好无损和受损的内聚力在使我们的模型与从数字地形模型获取的地形轮廓在火山口直径，火山口壁倾角以及深度和尺寸方面取得良好的匹配起着至关重要的作用。上露台。相反，中心坑的形状由玄武岩壳的受损摩擦系数控制，但主要受弹丸密度和速度影响。我们的结果证实了两层相对纯净的水冰，每层都具有不同的流变性和孔隙率，可以解释Arcadia Planitia中撞击坑的独特双台阶形态。我们发现冰的凝聚力较低，这可能表明降雪是该地区的进位机制。两个火山口地区冰层厚度的不同似乎暗示着整个阿卡迪亚平原上冰的沉积和/或演化历史的变化。