Distribution, Morphology and Structural Associations of Martian Pit Crater Chains
Distribution, Morphology and Structural Associations of Martian Pit Crater Chains
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火星坑坑链的分布、形态和结构关联
DOI：
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发表时间：
2003
期刊：
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通讯作者：
S. Colton
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作者：
D. Wyrick;D. Ferrill;D. W. Sims;S. Colton
简介：坑坑是圆形到椭圆形的塌陷特征，通常出现在排列（链）中，并合并成[1]，[2],[3],[4],[5]。我们已经开始使用火星轨道相机（MOC）数据系统地绘制火星西半球坑链的区域分布。坑链在阿尔巴帕特拉地区和水手谷沿线最为突出。在塔尔西斯山、诺克提斯迷宫和代达利亚平原以西的陨石坑地区也发现了它们。坑链显示出许多与伸展断裂系统相关的特征，通常发现于地堑内或向地堑过渡，尽管它们也发现于地堑系统之外。它们也以雁列排列出现，少数在雁列断裂或伸展裂缝的尖端显示类似于相互作用的弯曲尖端[6]。关于坑链形成的假设都需要大量空腔的形成和坍塌。坑链的形成机制如下：(i)脉群[1]，[2],[3],[4],[7]；塌陷的熔岩管（http://photojournal.jpl.nasa.gov/catalog/PIA03836）；或（iii）松散材料[8]下的裂缝。在这项研究中绘制的众多坑链中，很少有直接证据表明火山喷发或堤防的存在。塌陷熔岩管假说无法解释跨越多个熔岩流的坑链。初步结果表明，火星西半球的大多数坑链形成于与扩张正断层相关的裂缝上。方法：我们使用MOC广角和窄角图像系统地绘制了火星西半球的大片区域。广角图像的分辨率为每像素232米，用于绘制坑链的区域分布和方向。在研究区域，大约有1000个坑链被绘制出来，另外还有270个可能的坑链。采用分辨率为5 m / pixel的MOC窄角图像，对坑体形态进行了详细的研究。结果：分布与定位。Alba Patera地区有大量的深坑链，主要与Alba Patera相切，东侧为NE向，西侧为NW向。在阿尔巴帕特拉以南，这些链沿地堑体系的总体走向向南延伸。沿着水手谷，坑链也以东西方向出现，通常会合并成扇形槽。水手谷的西部是夜迷宫，在那里发现了许多方向上的坑链，它们之间有着有趣的交叉关系。夜迷路的坑链也通常表现为合并成扇形槽。在塔尔西斯火山阿斯克拉斯山、帕沃尼斯山和阿西亚山周围绘制了坑链。该地区的坑坑位于火山侧翼的同心圆上，较小数量的坑坑与火山呈放射状。在代达利亚平原的西部，在一个布满陨石坑的地区，坑链被映射成径向指向几个陨石坑。
Introduction: Pit craters are circular to elliptical collapse features that commonly occur in alignments (chains) and that coalesce into troughs [1], [2], [3], [4], [5]. We have begun systematically mapping the regional distribution of pit chains in the western hemisphere of Mars using the Mars Orbiter Camera (MOC) data. Pit chains are most prominent in the Alba Patera region and along the Valles Marineris. They are also found in Tharsis Montes, the Noctis Labyrinthus and in the cratered region west of Daedalia Planum. Pit chains display many features that are commonly associated with extensional fault systems, and are often found within grabens or transitioning into grabens, although they are also found apart from a graben system. They also occur in en echelon arrays and a few display curved tips similar to interaction at the tips of en echelon faults or extension fractures [6]. Hypotheses regarding the formation of pit chains all require formation and collapse of substantial cavities. The following mechanisms have been proposed for the formation of pit chains: (i) dike swarms [1], [2], [3], [4], [7]; (ii) collapsed lava tubes (http://photojournal.jpl.nasa.gov/catalog/PIA03836); or (iii) fissuring beneath loose material [8]. Of the numerous pit chains mapped during this research, few if any show direct evidence of volcanic eruption or the presence of a dike. The collapsed lava tube hypothesis fails to account for pit chains that cross multiple lava flows. Preliminary results indicate that most pit chains in the western hemisphere of Mars form over fissures associated with dilational normal faults. Methodology: We systematically mapped large regions of the western hemisphere of Mars using MOC wide angle and narrow angle images. The wide angle images have a resolution of 232 m per pixel and were used to map regional distribution and orientation of pit chains. In the study area approximately 1000 pit chains were mapped with an additional 270 possible pit chains. The MOC narrow angle images, with a resolution of 5 m per pixel, were used to study detailed pit morphology. Results: Distribution and orientation. Pit chains are numerous in the Alba Patera region, occurring mainly tangential to Alba Patera in a NE orientation on the eastern side and a NW orientation on the western side. South of Alba Patera these chains trend north-south following the general orientations of the graben system. Pit chains also occur in an east-west orientation along the Valles Marineris, typically coalescing into scalloped troughs. West of the Valles Marineris is the Noctis Labyrinthus, where pit chains are found in numerous orientations with interesting cross-cutting relationships. The pit chains in Noctis Labyrinthus also commonly appear to have coalesced into scalloped troughs. Pit chains were mapped around the Tharsis volcanoes of Ascraeus Mons, Pavonis Mons and Arsia Mons. Pit craters in this region were found in concentric rings on the flanks of the volcanoes and a smaller number were mapped radial to the volcanoes. To the west of Daedalia Planum, in a heavily cratered region, pit chains were mapped radial to several impact craters.