Thermal analysis of fractures at Cerberus Fossae, Mars : Detection of air convection in the porous debris apron
Thermal analysis of fractures at Cerberus Fossae, Mars : Detection of air convection in the porous debris apron
复制标题
火星 Cerberus Fossae 裂缝的热分析：多孔碎片围裙中空气对流的检测
DOI：
10.1016/j.icarus.2010.12.025
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发表时间：
2011
期刊：
影响因子：
3.2
通讯作者：
K.Kurita
中科院分区：
文献类型：
--
作者：
R.Antoine;T.Lopez;D.Baratoux;M.Rabinowicz;K.Kurita
这项研究调查了Cerberus Fossae夜间高温的原因，Cerberus Fossae是影响中央极乐平原的一个骨折系统。裂缝的内部部分（墙壁和地板）比周围的平原温度高40K。然而，一些温度剖面显示，在裂缝的中心部分出现了局部最低温度。我们首先检查了在断裂的几何形状导致天空比例大幅减少的情况下，夜间冷却效率的影响。然而，从提取的火星轨道激光高度计（MOLA）剖面计算得出的温度和天空比例之间缺乏相关性，这反驳了这一假设。反照率的变化也被考虑过，但似乎仅限于裂缝内，而且通常与温度无关。从高分辨率图像中推断出的基岩暴露、碎屑围裙和沙丘的热性质变化与裂缝内的温度变化无关。由于这些因素单独或联合使用都不能令人满意地解释裂缝内部和裂缝附近的温度变化，我们认为多孔碎屑围裙内空气对流输送的地热可能有助于解释夜间高温和裂缝底板局部极小值。用数值方法探讨了上述现象发生的条件及其对地表温度的影响。模拟中使用的保守地热梯度为20mW/m2，该值与推断出的塔尔西斯穹顶盾状火山下的岩石圈弹性厚度或火星热演化数值模拟预测的值一致。模型结果表明，在高达西速度（5×10−6m2）要求高渗透率的情况下，裂缝中部和上部的温差可以解释为10-20K。构成碎片围裙的粗糙材料的存在可能解释了为什么在Cerberus Fossae的背景下满足了这一关键标准。
This study investigates the cause of high nighttime temperatures within Cerberus Fossae, a system of fractures affecting the Central Elysium Planitia. The inner parts (walls and floor) of the fractures are up to 40K warmer than the surrounding plains. However, several temperature profiles exhibit a local temperature minima occurring in the central part of the fractures. We examined first the influence of cooling efficiency at night in the case of a strong reduction of the sky proportion induced by the fracture’s geometry. However, the lack of correlation between temperature and sky proportion, calculated from extracted Mars Orbiter Laser Altimeter (MOLA) profiles argues against this hypothesis. Albedo variations were considered but appear to be limited within the fractures, and are generally not correlated with the temperatures. Variations of the thermal properties of bedrocks exposures, debris aprons and sand dunes inferred from high-resolution images do not either correlate with temperature variations within the fractures. As none of these factors taken alone, or combined, can satisfactorily explain the temperature variations within and near the fracture, we suggest that geothermal heat transported by air convection within the porous debris aprons may contribute to explain high temperatures at night and the local minima on the fracture floor. The conditions for the occurrence of the suggested phenomenon and the consequences on the surface temperature are numerically explored. A conservative geothermal gradient of 20mW/m2was used in the simulations, this value being consistent with either inferred lithosphere elastic thicknesses below the shield volcanoes of the Tharsis dome or values predicted from numerical simulations of the thermal evolution of Mars. The model results indicate that temperature differences of 10–20K between the central and upper parts of the fracture are explained in the case of high Darcy velocities which require high permeability values (5×10−6m2). The presence of coarse material composing the debris aprons may explain why this key criteria was met in the context of Cerberus Fossae.