Thermal behavior of horizontally mixed surfaces on Mars
Thermal behavior of horizontally mixed surfaces on Mars
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DOI：
10.1016/j.icarus.2007.03.022
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发表时间：
2007-11-01
期刊：
影响因子：
3.2
通讯作者：
Mellon, Michael T.
中科院分区：
文献类型：
--
作者：
Putzig, Nathaniel E.;Mellon, Michael T.
目前从航天器对行星亮温的观测中推导热惯性的方法通常假设，对于任何给定的观测或同一地点的观测，表面性质都是均匀的。由于这种假设和温度与热惯性之间的非线性关系，亚像素水平不均匀性可能会在一天或季节的不同时间产生不同的表观热惯性。我们通过对各种理想化混合表面的热行为进行建模，研究了火星水平非均匀性的影响，这些表面包含不同比例的灰尘、沙子、硬壳以及不同角度和方位角的岩石或斜坡面。混合表面的热行为的垂直效应进行了研究。我们发现大（几个100 J m（-2）K-1 s（-1/2））的日变化和季节变化的表观热惯量，即使是小（类似于10%）混合物的材料具有适度对比的热性能或倾角。与层状表面的类似结果一起[Mellon，M.T.，Putzig，N.E.，2007.月球。sci.三十八.摘要2184]，这项工作表明，异质性对火星表面的热行为的影响是实质性的，并可能导致从航天器仪器得出的表观热惯性的大变化。虽然我们的研究结果警告不要过度解释从中值或平均图或从单一温度测量得出的热惯性，但它们也表明，使用一套从一天中的一系列时间和季节的单一观测得出的表观热惯性值来限制火星表面的异质性是可能的。(C)2007年爱思唯尔公司All rights reserved.
Current methods for deriving thermal inertia from spacecraft observations of planetary brightness temperature generally assume that surface properties are uniform for any given observation or co-located set of observations. As a result of this assumption and the nonlinear relationship between temperature and thermal inertia, sub-pixel horizontal heterogeneity may yield different apparent thermal inertia at different times of day or seasons. We examine the effects of horizontal heterogeneity on Mars by modeling the thermal behavior of various idealized mixed surfaces containing differing proportions of either dust, sand, duricrust, and rock or slope facets at different angles and azimuths. Latitudinal effects on mixed-surface thermal behavior are also investigated. We find large (several 100 J m(-2) K-1 s(-1/2)) diurnal and seasonal variations in apparent thermal inertia even for small (similar to 10%) admixtures of materials with moderately contrasting thermal properties or slope angles. Together with similar results for layered surfaces [Mellon, M.T., Putzig, N.E., 2007. Lunar Planet. Sci. XXXVIII. Abstract 2184], this work shows that the effects of heterogeneity on the thermal behavior of the martian surface are substantial and may be expected to result in large variations in apparent thermal inertia as derived from spacecraft instruments. While our results caution against the over-interpretation of thermal inertia taken from median or average maps or derived from single temperature measurements, they also suggest the possibility of using a suite of apparent thermal inertia values derived from single observations over a range of times of day and seasons to constrain the heterogeneity of the martian surface. (C) 2007 Elsevier Inc. All rights reserved.