A Novel Surface Energy Balance Method for Thermal Inertia Studies of Terrestrial Analogs

Surface thermal inertia derived from satellite imagery offers a valuable tool for remotely mapping the physical structure and water content of planetary regolith. Efforts to quantify thermal inertia using surface temperatures on Earth, however, have consistently yielded large uncertainties and suffered from a lack of reproducibility. Unlike dry or airless bodies, Earth’s abundant water and dense atmosphere lead to dynamic thermophysical conditions that are a greater challenge to model than on a world like Mars. In this work, an approach was developed using field experiments to inform and fine-tune a thermophysical model of terrestrial sediment and calculate an inherent thermal inertia value with higher precision and less initial knowledge of the sediment than has previously been achieved remotely on Earth. A thermal inertia derived for a basaltic tephra site in Northern Arizona was replicated within 1% between different field seasons, demonstrating reproducibility. Model-derived values were validated in situ by two different thermophysical field probes to within 8% of the measured mean values. Analog studies such as this hold the promise of improved interpretations of surface materials on Mars, and an accurate thermal model for Earth is the key step to enabling translation between the two worlds.

基于卫星影像反演得到的表面热惯量（surface thermal inertia）是一种可用于遥感测绘行星风化层（planetary regolith）物理结构与含水量的有效工具。然而，利用地表温度量化地球表面热惯量的相关研究始终存在较大不确定性，且难以实现可重复性。与干燥或无大气天体不同，地球拥有充足的水资源与稠密大气层，其动态变化的热物理条件相较于火星等天体更难进行建模。本研究开发了一种基于野外实验的方法，用于优化并微调地表沉积物的热物理模型，相比此前地球表面的遥感反演方法，该方法在仅需更少沉积物先验知识的前提下，可计算得到精度更高的固有热惯量值。针对亚利桑那州北部一处玄武质火山碎屑测点反演得到的热惯量，在不同野外考察季间的重现误差小于1%，证明了该方法具备可重复性。通过两款不同的热物理野外探头开展原位（in situ）验证，模型计算得到的热惯量值与实测平均值的偏差均控制在8%以内。此类类比研究有望提升对火星表面物质的解译精度，而构建精准的地球热物理模型，则是实现两大天体间热惯量参数跨尺度转换的关键步骤。