Optical scattering properties of terrestrial varnished basalts compared with rocks and soils at the Viking Lander sites
Optical scattering properties of terrestrial varnished basalts compared with rocks and soils at the Viking Lander sites
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陆地涂漆玄武岩的光学散射特性与维京登陆器地点的岩石和土壤的比较
DOI：
10.1029/97je03018
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
M. Shepard
中科院分区：
文献类型：
--
作者：
E. Guinness;R. Arvidson;I. Clark;M. Shepard
加州皮斯加火山区的玄武岩流被风成粉砂大小的沉积物覆盖。明亮的地幔上覆盖着一层致密的玄武岩鹅卵石路面，这些鹅卵石经过风成磨蚀而变得光滑，并涂上了有光泽的深灰色和红色沙漠清漆。相比之下，火星上的两个维京海盗着陆点缺乏沙漠路面，岩石有光泽的表面，在某些情况下比土壤更亮。为了进一步研究涂清漆的玄武岩鹅卵石的散射特性，并与火星岩石进行比较，实验室测量了涂清漆和新鲜玄武岩表面的双向反射率（中心波长为0.69 μm）随入射角和发射角沿着主平面的变化。反射率数据与散射模型（包括粗糙表面的镜面反射以及体积穿透和反射）拟合，表明红色涂漆表面具有比深灰色涂漆表面更高的单次散射反射率和更高的表面粗糙度值（分别为0.56和0.42; 21°和17°）。新鲜切割表面的值最低（0.40和6°）。结果是一致的，从薄的部分，这些表面和现场观察表明，深灰色的清漆表面光滑暴露于风磨损的意见。深红色涂漆表面往往更粗糙，因为它们嵌入风成地幔中，并在受保护的环境中发展。将该模型应用于大气校正、辐射校准的维京海盗号着陆器图像（0.60至0.74 μm）表明，许多岩石比土壤更光滑，单次散射角比土壤更高（分别为9°对27°; 0.71对0.63）。结果与火星表面的岩石因风成磨损而变得光滑并被大气尘埃覆盖的模型一致。火星上缺乏沙漠路面可能与缺乏鹅卵石和缺乏土壤形成过程有关。类似的明亮，光滑的涂层预计在火星上的其他地点，包括探路者战神谷网站。
Basalt flows at the Pisgah Volcanic Field, California, are mantled by aeolian silt-sized deposits. The bright mantle is overlain by a dense pavement of basalt cobbles smoothed by aeolian abrasion and coated with glossy dark gray and red desert varnishes. In contrast, the two Viking landing sites on Mars lack desert pavements, and rocks have glossy surfaces that in some cases are brighter than soils. To pursue further the scattering characteristics of varnished basalt cobbles for comparison to Mars rocks, laboratory measurements of bidirectional reflectance (0.69 μm center wavelength) were made as a function of incidence and emission angle along the principal plane for varnished and fresh basalt surfaces. The reflectance data, fit with a scattering model that includes specular reflections from rough surfaces and volume penetration and reflection, show that the red varnished surfaces have higher single scattering albedoes and higher surface roughness values than the dark gray varnished surfaces (0.56 and 0.42; 21° and 17°, respectively). Fresh cut surfaces have lowest values (0.40 and 6°). Results are consistent with observations made from thin sections for these surfaces and with field observations that show dark gray varnished surfaces are smoothed by exposure to wind abrasion. Dark red varnished surfaces tend to be rougher because they are embedded in the aeolian mantle and develop in a protected environment. Application of the model to atmospherically corrected, radiometrically calibrated Viking Lander images (0.60 to 0.74 μm) shows that many rocks are smoother and have single scattering albedoes higher than soils (9° versus 27°; 0.71 versus 0.63, respectively). Results are consistent with a model in which rocks at the surface of Mars become smoothed by aeolian abrasion and coated with atmospheric dust. Lack of desert pavement on Mars is probably associated with a scarcity of cobbles and a lack of soil forming processes. Similar bright, smooth coatings are expected at other locations on Mars, including the Pathfinder Ares Vallis site.