Ground ice at the Phoenix Landing Site: Stability state and origin
Ground ice at the Phoenix Landing Site: Stability state and origin
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DOI：
10.1029/2009je003417
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发表时间：
2009-12-17
影响因子：
4.8
通讯作者：
Zent, Aaron P.
中科院分区：
文献类型：
--
作者：
Mellon, Michael T.;Arvidson, Raymond E.;Zent, Aaron P.
凤凰号任务的一个主要目标是研究火星上高纬度地面冰的特征。我们报道了对地面冰的观测，它的深度分布和稳定性特征，并考察了它的起源和历史。通过十几个海沟复合体和着陆推进器坑，在一系列多边形形态省份上探索了高纬度地面冰。在一层相对松散的无冰土壤下发现了丰富的浅层地面冰，平均深度为4.6厘米，不同沟渠之间的差异超过10倍。这些变化主要可以归因于坡度效应和覆盖层土壤中影响地面温度的热惯性变化。在这个深度，冰的存在符合水汽扩散平衡，平均大气水分含量为3.4×10(19)m(-3)，与当今的气候一致。观测到了显著的冰的不均一性，主要有两种形式：冰胶结土和相对纯净的浅色冰。冰胶结土约占挖沟暴露出的冰质材料的90%，最好的解释是蒸汽在基质支撑的多孔土壤中沉积了孔隙冰。浅色调的冰沉积只占地下的一小部分，被认为是由相对较薄的近地表沉积组成的。这些相对纯净的冰沉积的来源似乎与土壤冰分离形成的过剩冰最一致，例如通过薄膜迁移和冰透镜、针状冰或类似冰结构的形成。
A primary objective of the Phoenix mission was to examine the characteristics of high latitude ground ice on Mars. We report observations of ground ice, its depth distribution and stability characteristics, and examine its origins and history. High latitude ground ice was explored through a dozen trench complexes and landing thruster pits, over a range of polygon morphological provinces. Shallow ground ice was found to be abundant under a layer of relatively loose ice-free soil with a mean depth of 4.6 cm, which varied by more than 10x from trench to trench. These variations can be attributed mainly to slope effects and thermal inertia variations in the overburden soil affecting ground temperatures. The presence of ice at this depth is consistent with vapor-diffusive equilibrium with respect to a mean atmospheric water content of 3.4 x 10(19) m(-3), consistent with the present-day climate. Significant ice heterogeneity was observed, with two major forms: ice-cemented soil and relatively pure light toned ice. Ice-cemented soils, which comprised about 90% of the icy material exposed by trenching, are best explained as vapor deposited pore ice in a matrix supported porous soil. Light toned ice deposits represent a minority of the subsurface and are thought to consist of relatively thin near surface deposits. The origin of these relatively pure ice deposits appears most consistent with the formation of excess ice by soil ice segregation, such as would occur by thin film migration and the formation of ice lenses, needle ice, or similar ice structures.