The formation of fluidized ejecta on Mars by granular flows
The formation of fluidized ejecta on Mars by granular flows
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DOI：
10.1111/j.1945-5100.2006.tb00435.x
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发表时间：
2006-10
影响因子：
2.2
通讯作者：
K. Wada;O. Barnouin-Jha
中科院分区：
文献类型：
--
作者：
K. Wada;O. Barnouin-Jha
翻译后摘要-一个简单的颗粒流模型是用来调查一些条件下，喷出物可能会流动作为一个颗粒介质。这项研究的目的是提供一些界限，说明何时需要挥发物或大气来解释许多火星喷出物沉积物的流体状形态。我们认为，当喷出物幕第一次击中目标表面通过弹道和可能的流动之后，喷出物沉积过程。一个新的发现是，无论是硬光滑表面或轻微侵蚀表面允许喷出物容易流动作为颗粒介质。既不需要挥发物也不需要大气来启动流动。喷出物颗粒之间的低摩擦系数也可以产生流动，类似于向喷出物中添加挥发物。粗糙或密集的可侵蚀表面的存在不允许喷出物容易流动。喷出物颗粒之间的高摩擦系数也会阻止流动，而恢复系数（粒子之间碰撞后保留多少能量的度量）的变化在喷出物的流动动力学中起着次要作用。火星上过去的河流活动可能会产生一个坚硬光滑或有点易侵蚀的表面，它可以使表面硬化，侵蚀和光滑表面，或者产生相当容易侵蚀的沉积地形。我们的模型没有产生壁垒或分层喷出物形态，但这可能是因为我们的模型中使用了几个简化的假设，不应该被解释为证明，无论是挥发物或大气需要形成流化喷出物形态。
Abstract— A simple granular flow model is used to investigate some of the conditions under which ejecta may flow as a granular media. The purpose of this investigation is to provide some bounds as to when either volatiles or an atmosphere are required to explain the fluid‐like morphology of many Martian ejecta deposits. We consider the ejecta deposition process from when an ejecta curtain first strikes a target surface via ballistics and possibly flows thereafter. A new finding is that either hard‐smooth surfaces or slightly erodible surfaces allow ejecta to flow readily as a granular medium. Neither volatiles nor an atmosphere are required to initiate flow. A low friction coefficient between ejecta grains can also generate flow and would be analogous to adding volatiles to the ejecta. The presence of either a rough or a densely packed erodible surface does not permit easy ejecta flow. High friction coefficients between ejecta grain also prevent flow, while changes in the coefficient of restitution (a measure of how much energy is retained after collisions between particles) plays a minor role in the flow dynamics of ejecta. A hard smooth or a somewhat erodible surface could be generated by past fluvial activity on Mars, which can either indurate a surface, erode and smooth a surface, or generate sedimentary terrains that are fairly easy to erode. No ramparts or layered ejecta morphologies are generated by our model, but this may be because several simplifying assumptions are used in our model and should not be construed as proof that either volatiles or an atmosphere are required to form fluidized ejecta morphologies.