Asymmetric signatures in simple craters as an indicator for an oblique impact direction
Asymmetric signatures in simple craters as an indicator for an oblique impact direction
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简单陨石坑中的不对称特征作为倾斜撞击方向的指示
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
T. Kenkmann
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文献类型：
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作者：
M. Poelchau;T. Kenkmann
摘要在撞击角度小于45°的倾斜撞击中，远端喷出物毯子的两侧形状是衡量撞击向量的最强指标。这种两侧的对称性被减弱，并被朝向陨石坑边缘的径向对称性叠加，在撞击角度降至10-15°时，火山口边缘保持圆形。双侧对称性的残留物可能仍然存在于最近端的喷射物、翻转的襟翼和火山口边缘，目的是推断撞击向量。提出了一个模型，该模型利用近端喷射物的轨迹来假定两侧的模式，并在环形山边缘的层理平面的方向上预测这些模式。这个模型被成功地与火星上倾斜的图廷陨石坑近端喷出物毯子中的径向凹槽描述的图案相关联。开发了一种新的方法来检测构造不对称性，方法是将层理数据转换为表示陨石坑边缘相对于陨石坑中心的同心走向方向的偏差的值，称为同心偏差。该方法被应用于西澳大利亚沃尔夫克里克陨石坑的现场数据。翻转的襟翼中的层理意味着来自东部的冲击器，这完善了早期的出版物，而来自内缘的层理与火山口边缘的形态相关联。
Abstract— In oblique impacts with an impact angle under 45°, the bilateral shape of the distal ejecta blanket is used as the strongest indicator for an impact vector. This bilateral symmetry is attenuated and is superimposed by radial symmetry towards the crater rim, which remains circular for impact angles down to 10–15°. The possibility that remnants of bilateral symmetry might still be present in the most proximal ejecta, the overturned flap and the crater rim was explored with the intention of deducing an impact vector. A model is presented that postulates bilateral patterns using proximal ejecta trajectories and predicts these patterns in the orientation of bedding planes in the crater rim. This model was successfully correlated to patterns described by radial grooves in the proximal ejecta blanket of the oblique Tooting crater on Mars. A new method was developed to detect structural asymmetries by converting bedding data into values that express the deviation from concentric strike orientation in the crater rim relative to the crater center, termed “concentric deviation.” The method was applied to field data from Wolfe Creek crater, Western Australia. Bedding in the overturned flap implies an impactor striking from the east, which refines earlier publications, while bedding from the inner rim shows a correlation with the crater rim morphology.