Cratering on Mars with almost no atmosphere or volatiles: Pangboche crater
Cratering on Mars with almost no atmosphere or volatiles: Pangboche crater
复制标题
火星上几乎没有大气或挥发物的陨石坑：庞博切陨石坑
DOI：
--
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
P. Mouginis
中科院分区：
文献类型：
--
作者：
P. Mouginis
Pangboche火山口（北纬17.2°，东经226.7°，直径10.4公里）位于火星奥林匹斯山火山峰顶附近，海拔约20.9公里。考虑到大气的尺度高度为11.1公里，这个相对较大的新陨石坑很可能是在大气压力<1毫巴的情况下形成的，基本上是在不挥发的年轻熔岩流中形成的。高分辨率成像科学实验（HiRISE）和背景相机（CTX）图像对Pangboche陨石坑的详细分析表明，挥发性相关特征（例如，流化的喷出物层和坑状的地面物质）不存在。相比之下，陨石坑的底部、内壁和边缘发生了大量的撞击融化，并且从边缘顶部延伸到大约45公里处有大量的次级陨石坑。所有这些特征都表明，在陨石坑形成时，目标岩石中缺乏挥发物，而不是稀薄的大气，对陨石坑的形态产生了控制作用。来自CTX图像的数字高程数据显示，Pangboche陨石坑的深度约为954米（深度/直径约为0.092），凸起的目标岩石占180米高的北缘地形的58%左右。由于目标物质由一系列分层熔岩流组成，Pangboche陨石坑很可能代表了火星上与月球上形成的陨石坑（允许研究引力效应的变化）或水星上形成的陨石坑（允许研究大气的作用）直接比较的最佳陨石坑。
Pangboche crater (17.2°N, 226.7°E; 10.4 km dia.) lies close to the summit of Olympus Mons volcano, Mars, at an elevation of ~20.9 km above the datum. Given a scale height of 11.1 km for the atmosphere, this relatively large fresh crater most likely formed at an atmospheric pressure <1 mbar in essentially volatile‐free young lava flows. Detailed analysis of Pangboche crater from High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) images reveals that volatile‐related features (e.g., fluidized ejecta layers and pitted floor material) are absent. In contrast, abundant impact melt occurs on the floor, inner walls, and rim of the crater, and there is an extensive field of secondary craters that extend up to approximately 45 km from the rim crest. All of these attributes argue that it was the absence of volatiles in the target rocks at the time of crater formation, rather than the thin atmosphere, which had a controlling influence on crater morphology. Digital elevation data derived from the CTX images reveal that Pangboche crater has a depth of about 954 m (depth/diameter = approximately 0.092) and that uplifted target rocks comprise about 58% of the relief of the 180 m‐high north rim. As the target material comprised a sequence of layered lava flows, Pangboche crater may well represent the best crater on Mars for direct comparison with craters formed on the Moon (permitting variations in gravitational effects to be investigated) or on Mercury (allowing the role of the atmosphere to be studied).