Geology of Xanthe Terra outflow channels and the Mars Pathfinder landing site
Geology of Xanthe Terra outflow channels and the Mars Pathfinder landing site
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Xanthe Terra 流出通道和火星探路者号着陆点的地质
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
R. Greeley
中科院分区：
文献类型：
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作者：
D. M. Nelson;R. Greeley
选择火星探路者着陆点是因为它位于火星上的战神和Tiu Valles流出通道的入口处，在那里，各种地质单元的沉积物可能在湖泊环境中积累。最近的地质测绘在1：2米的比例尺的Xanthe Terra渠道和Chryse Planitia附近MPLS揭示了一个进程的河流侵蚀和沉积在整个西方时期。根据地质学，推断出河道的分水岭，并制作了一系列古地质图。三个流出事件被确认：（1）广泛的席状水在早期西方，从东部的水手谷和赤道混乱地区，与最初的侵蚀到高原高原基底，（2）早期通道的形成，和（3）随后的洪水加深的通道，其目前的形态。西斯姆德和提乌山谷最近一次洪水发生在西斯姆德和提乌山谷晚期，通过地层叠加、沿着河道底部的条纹以及洪水方向上流线型岛屿的方向来指示。这表明，在MPLS沉积的表层沉积物最有可能来自这些渠道，并在较小程度上来自战神谷。一个排名计划，以评估潜在的来源，发现在MPLS的沉积物。据推测，最丰富的物质来自诺亚纪和西方高原平原，以及以前洪水的沉积物。早期洪水的底层物质也可以在MPLS发现，作为附近撞击坑的喷出物。
The Mars Pathfinder landing site (MPLS) was selected for its location at the mouths of Ares and Tiu Valles outflow channels on Mars, where sediments from a variety of geologic units could have accumulated in a lacustrine environment. Recent geologic mapping at 1:2 M scale of the Xanthe Terra channels and Chryse Planitia near MPLS reveals a progression of fluvial erosion and deposition throughout the Hesperian period. From the geology, the watersheds of the channels were inferred, and a sequence of paleogeologic maps was produced. Three outflow episodes are recognized: (1) broad sheetwash during the early Hesperian, emanating from eastern Valles Marineris and equatorial chaos regions, with initial erosion into highland plateau basement, (2) early channel formation, and (3) subsequent flooding which deepened the channels to their current morphologies. The most recent flooding issued from Simud and Tiu Valles during the late Hesperian, indicated by stratigraphic superposition, striations along the floor of the channel, and the orientation of streamlined islands in the flood direction. This suggests that surface sediments deposited at MPLS are most likely to have come from these channels, and to a lesser extent from Ares Vallis. A ranking scheme was developed to assess the potential origins for the sediments found at MPLS. The most abundant materials are inferred to have come from the Noachian and Hesperian highland plains and reworked sediments from previous floods. Underlying materials from earlier floods could also be found at MPLS as ejecta from nearby impact craters.