New insights into Martian dust distribution and water‐ice cloud microphysics
New insights into Martian dust distribution and water‐ice cloud microphysics
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对火星尘埃分布和水冰云微物理的新见解
DOI：
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发表时间：
2002
期刊：
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通讯作者：
M. Cabane
中科院分区：
文献类型：
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作者：
F. Montmessin;P. Rannou;M. Cabane
在本文中，我们使用了一种直接的方法，结合了火星大气的微物理和光度模拟。这种方法使我们能够重现被火星边缘的雾霾散射的光的垂直轮廓。随后的结果与海盗号轨道飞行器相机提供的多色图像进行了比较。我们研究的“自由参数”与垂直输运和粉尘粒度分布有关。为了获得最令人满意的多光谱模型剖面，我们进行了一项敏感性研究，包括相关的参数范围。除了亚微米颗粒（reff ~ 0.2 μm）的不太可能分布外，没有得到一致的拟合。这意味着以前的研究提出的尘埃的大小分布与目前的分析不一致。这种明显的差异可以通过在先前从维京着陆器图像中提取的尺寸分布中添加一个单独的亚微米颗粒峰来解决。只有在这种情况下，才能成功匹配雾霾的光谱和垂直结构。虽然双峰分布会改变目前火星尘埃的图像，但这种分布是地球沙漠中土壤衍生气溶胶大小函数的常见表示。我们还试图从维京号的肢体图像中获取信息。我们估计云粒子的有效半径约为1.2 ~ 1.8 μm，而云的可见不透明度为0.02。
[1] In this paper we use a direct method which combines microphysics and photometric simulations of the Martian atmosphere. This approach allows us to reproduce vertical profiles of the light scattered by the haze at the limb of Mars. Subsequent results are compared to a multiple-color image provided by the Viking Orbiter camera. The “free parameters” of our study are related to vertical transport and dust size distribution. A sensitivity study has been conducted, encompassing a relevant range of parameters, in order to obtain the most satisfying multispectral modeled profile with respect to the one inferred from data. Except for an unlikely distribution of submicron particles (reff ∼ 0.2 μm), no consistent fit can be obtained. This implies that size distributions of dust suggested by previous studies are not in agreement with the present analysis. This apparent discrepancy can be resolved by adding a separate peak of submicron particles to the size distribution previously extracted from Viking Lander images. Only in that case can spectral and vertical structures of haze be successfully matched. While a bimodal distribution would change the current picture of Martian dust, such distribution is a common representation of soil-derived aerosol size function in Earth deserts. We also attempted to derive information from the cloud shown in the Viking limb image. Our estimates suggest that cloud particle effective radius is around 1.2–1.8 μm, while the cloud visible opacity is 0.02.