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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Properties of dust in the Martian atmosphere from the Imager on Mars Pathfinder
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Properties of dust in the Martian atmosphere from the Imager on Mars Pathfinder

机译：火星探路者成像仪在火星大气中的尘埃特性

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The Imager for Mars pathfinder (IMP) returned sequences of images of the Martian sky characterizing the size distribution, optical constants, and nature of the aerosols suspended in the atmosphere of Mars. These sequences were executed when the solar elevation angle was approximately 15 deg and consisted of images near the elevation of the Sun, spanning a range in azimuth from about 4 deg to 180 deg from the Sun. Images were obtained at four wavelengths from 444 to 965 nm. From one sequence of observations, results are shown from a comparison of absolute photometry of the Martian sky with multiple scattering models. Results include the following. (1) The geometric cross-section-weighted mean particle radius is 1.6 +- 0.15 #mu#m almost independent of the assumed width (variance) of the size distribution. (2) The imaginary refractive index shows a steep increase with wavelength from 670 nm to shorter wavelengths, and a shallow increase toward longer wavelengths, consistent with the reflection spectrum observed by IMP for Martian soil. (3) For each assumed variance, two parameters governing the slope and curvature of the portion of the phase function due to internally transmitted light are found uniquely as functions of wavelength. (4) The variance of the gamma size distribution is difficult to constrain from these observations alone. The shape of the single scattering phase functions derived from the IMP observations is compared to laboratory measurements of powder samples. One sample of irregular particles has a single scattering phase function quite similar to that derived for Mars. Overall, the results for the mean cross-section-weighted size and imaginary refractive index as a function of wavelength are in remarkably good agreement with the revised analysis by Pollack et al. [1995] of the observations made by the Viking lander 20 years earlier.
机译：火星成像探路者（IMP）返回火星天空的图像序列，这些序列表征了悬浮在火星大气中的气溶胶的大小分布，光学常数和性质。当太阳仰角约为15度时执行这些序列，并且这些序列由接近太阳仰角的图像组成，这些图像的方位角范围距离太阳大约4度到180度。在444至965 nm的四个波长下获得图像。从一个观测序列中，通过对火星天空的绝对光度学与多个散射模型的比较显示了结果。结果包括以下内容。 （1）几何截面加权平均颗粒半径为1.6±0.15＃μm，几乎与尺寸分布的假定宽度（方差）无关。 （2）假想折射率随着波长从670 nm到较短波长的增加而急剧增加，而向较长波长的增加则略有增加，这与IMP对火星土壤观察到的反射光谱一致。 （3）对于每个假定的方差，唯一确定两个参数，该参数控制由于内部传输的光而导致的相位函数部分的斜率和曲率与波长的关系。 （4）仅从这些观察结果就很难限制伽玛大小分布的变化。将来自IMP观测值的单个散射相函数的形状与粉末样品的实验室测量结果进行比较。一个不规则粒子的样本具有与散射火星非常相似的单个散射相位函数。总的来说，平均横截面加权尺寸和虚构折射率随波长变化的结果与Pollack等人的修正分析非常吻合。 [1995]维京号着陆器20年前的观测结果。

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