Small‐scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost
Small‐scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost
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DOI：
10.1029/97je02582
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发表时间：
1997-11
影响因子：
--
通讯作者：
M. Mellon
中科院分区：
文献类型：
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作者：
M. Mellon
建立了火星富冰多年冻土热应力的时间相关粘弹性模型，以检验从轨道和维京登陆器2号观测到的小尺度多边形特征是热收缩破裂的结果，这一假设通常发生在陆地永久冻土中。结果表明，由于地温的季节性循环，火星富冰永久冻土中出现了显著的拉应力。使用适用于低温冰层的保守流变学参数，北纬约20°至30°的拉应力极易超过抗拉强度(假定为2至3兆帕)，因此很容易形成断裂。在赤道地区，特殊的条件可能会使拉应力接近抗拉强度。这些结果支持了观测到的小尺度多边形特征的热收缩起源，并强调了这些特征作为地面冰的有价值的形态指标的实用性。
A time-dependent viscoelastic model of thermal stress in Martian ice-rich permafrost is developed to test the hypothesis that small-scale polygonal features observed from orbit and by the Viking Lander 2 are the result of thermal contraction cracking, as commonly occurs in terrestrial permafrost. Results indicate that significant tensile stress occurs in Martian ice-rich permafrost as a result of seasonal cycles in the ground temperature. Using conservative rheological parameters appropriate for ice at low temperatures, tensile stresses poleward of about 20° to 30° latitude easily exceed the tensile strength (assumed to be 2 to 3 MPa) and fractures should readily form. In the equatorial regions, special conditions may allow tensile stresses to approach the tensile strength. These results support a thermal contraction origin of observed small-scale polygonal features and emphasize the utility of these features as valuable morphological indicators of ground ice.