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首页> 外文期刊>Journal of geophysical research. Planets >Mechanisms and timescales of fluvial activity at Mojave and other young Martian craters
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Mechanisms and timescales of fluvial activity at Mojave and other young Martian craters

机译：莫哈韦沙漠和其他年轻火星陨石坑河流活动的机制和时间尺度

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Mojave Crater, and five other relatively young Late Hesperian to Amazonian-age Martian craters exhibit channelized alluvial fans that are sourced from bedrock-eroded catchments. These catchments emerge from the crests of sloping surfaces, suggesting a formation mechanism that involved precipitation. The evidence for fluvial activity at all six craters is restricted to their interiors and the immediate surrounding regions. Detailed mapping at Mojave reveals the highest density of channels, catchments and fans interior to the crater. Similar landforms are identified outside of the crater, but not beyond ~200 kmfromthe rim. Irregular pits on the floor ofMojave, interpreted as degassing structures fromhot impact melt, directly superpose several fan surfaces, and partly destroy the fan toes. This suggests that sediment was mobilized immediately after crater formation, while the crater was still hot. Based on the patterns and timing of channel-fan development at all six craters we favor several hypotheses for the precipitation mechanism: (1) snowfall and melt on young, hot impact craters, (2) impact plume precipitation, and (3) degassing of volatiles from impact melt terrain. Scenario (1) suggests a different global or regional climate relative to modern conditions, requiring equatorial and midlatitude snowfall accumulation. Scenarios (2) and (3) do not necessarily require unique climate conditions, as water may have been mobilized from the target or the impactor.
机译：莫哈韦陨石坑和另外五个相对较年轻的晚黑斯佩里亚人到亚马孙时代的火星陨石坑都展示了渠道冲积扇，这些扇冲扇源于被基岩侵蚀的流域。这些集水区是从倾斜表面的顶峰出现的，表明了涉及降水的形成机制。所有六个陨石坑的河流活动的证据仅限于其内部和附近区域。莫哈韦沙漠（Mojave）的详细地图显示了火山口内部通道，集水区和风扇的最高密度。在火山口外也可以找到类似的地貌，但距离边缘不到200公里。莫哈韦沙漠地板上不规则的凹坑，被解释为是由热冲击熔体脱气的结构，直接叠加在多个风扇表面上，部分破坏了风扇的脚趾。这表明在火山口仍很热的情况下，火山口形成后立即动员了沉积物。根据所有六个陨石坑通道扇形发育的模式和时机，我们支持以下几种降水机理的假设：（1）年轻的热撞击陨石坑降雪和融化;（2）撞击羽流沉淀;（3）脱气来自冲击的挥发物融化了地形。方案（1）提出了与现代条件不同的全球或区域气候，需要赤道和中纬度降雪积聚。方案（2）和（3）不一定需要独特的气候条件，因为可能已经从目标或撞击者处调集了水。

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