Late-stage formation of Martian chloride salts through ponding and evaporation
Late-stage formation of Martian chloride salts through ponding and evaporation
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DOI：
10.1130/g36895.1
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发表时间：
2015-09-01
期刊：
影响因子：
5.8
通讯作者：
Kierein-Young, Kathryn S.
中科院分区：
文献类型：
--
作者：
Hynek, Brian M.;Osterloo, Mikki K.;Kierein-Young, Kathryn S.
通过使用多光谱轨道数据，已经在火星上的数百个地点记录了少量氯盐的沉积。考虑到这些沉积物的空间范围很小，它们的形成机制、时间以及与火星历史上其他水作用的关系目前还没有得到很好的约束。在这里，我们详细介绍了机遇号火星车所在的子午线平面附近的一个氯化物矿藏。这种氯化物沉积可能是由河湖作用形成的，暗示着一个活跃的水文循环。后期活动导致周围高地的山谷切割，并在当地盆地积水形成湖泊。湖的水位最终上升，冲破了排水分水岭，导致了大量的外流。剩下的水蒸发了，最终使氯化物沉淀到最低水平。通过数字地形模型，利用湖泊和盐滩的体积来计算湖泊的盐度，在整个湖泊范围内，盐度类似于地球海洋盐度的8%。在出口山谷横切的地形上进行的陨石坑密度测量将最大年龄限制在3.60Ga。这一水文事件发生在区域广泛的河流切割之后，也发生在机遇号正在调查的硫酸盐基岩形成之后。我们的结论是，这个和其他类似的氯化物矿床是矿物学记录中记录的火星上最后可居住的地表水的一些残留物。
Small deposits of chloride salts have been documented at hundreds of locations on Mars through the use of multispectral orbital data. Given the small spatial extent of these deposits, their formation mechanisms, timing, and relation to other aqueous processes in Mars' history are presently poorly constrained. Here we detail one of the chloride deposits near Meridiani Planum, the location of the Opportunity rover. This chloride deposit likely formed from fluviolacustrine processes, implying an active hydrologic cycle. Late-stage activity led to valley incision in the surrounding highlands and ponding of water to form a lake in a local basin. The lake level eventually rose and breached the drainage divide, leading to significant outflow. The remaining water evaporated and eventually precipitated the chlorides at the lowest levels. Through digital terrain models, the lake and salt flat volumes were used to calculate the salinity of the lake, which at full lake extent was similar to 8% of the salinity of Earth's oceans. Crater density measurements on the terrain cross-cut by the outlet valley constrain the maximum age to 3.60 Ga. This hydrological episode occurred after regional widespread fluvial incision and also post-dates formation of the sulfate bedrock being investigated by Opportunity. We conclude that this and other similar chloride deposits represent some of the last vestiges of habitable surface water on Mars as recorded in the mineralogical record.