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首页> 外文期刊>Journal of geophysical research. Planets >Characteristics of large Martian dust devils using Mars Odyssey Thermal Emission Imaging System visual and infrared images
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Characteristics of large Martian dust devils using Mars Odyssey Thermal Emission Imaging System visual and infrared images

机译：火星奥德赛热发射成像系统可视和红外图像显示的大型火星尘埃魔鬼的特征

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A search for Martian dust devils has been carried out, using Mars Odyssey Thermal Emission Imaging System (THEMIS) visible-wavelength images. Simultaneous THEMIS thermal infrared wavelength images were then processed and analyzed to investigate the thermal properties of the dust devils observed; 3079 images were checked, concentrating on northern spring, summer, and autumn (LS from 0° to 270°, 20°S to 50°N). Mars Express High Resolution Stereo Camera, Mars Global Surveyor Mars Orbiter Camera, and other THEMIS visible images were used for comparison to potentially rule out any ambiguous geological features. Eight clear examples of dust devils have been found in five separate images, with a comparable number of unconfirmed possible devils. The rarity of dust devils observed is believed to result from a combination of the difficulty in identifying dust devils in medium resolution THEMIS data and the fact that the Mars Odyssey orbit flyover local time is later in the afternoon than would be optimum for dust devil searching. The temporal distribution of dust devil activity appears to be weighted more toward later afternoon, compared to Earth, but this may be a sampling effect due to size variation with time of sol, greater coverage later in the sol, or the small-number statistics. The thermal infrared images indicate that the lofted dust in the column is cooler than the surrounding surface and must be equilibrating with the atmosphere in the dust devil. This energy transfer is estimated to be about 10% of the heat flux energy that is available to drive the systems. The ground shadowed by the dust column also appears colder than the surroundings, because of reduced solar illumination. From the visible-wavelength images, the shadows of the dust columns were used to estimate the column opacity, which in turn gave estimates of the dust loadings, which ranged from 1.9 × 10?5 to 1.5 × 10?4 kg m?3, similar to lander-based observations. No thermal or visible trails are associated with the dust devils, indicating that the surface equilibrates quickly after the devil has passed and that track counting as a dust devil survey technique must underestimate dust devil populations and consequently dust loading calculations, confirming previous work.
机译：使用火星奥德赛热发射成像系统（THEMIS）可见波长图像，对火星尘埃魔鬼进行了搜索。然后处理并分析了同步的THEMIS热红外波长图像，以研究观察到的尘埃的热学性质。检查了3079张图像，重点放在北部的春季，夏季和秋季（最低气温从0°到270°，从20°S到50°N）。使用Mars Express高分辨率立体相机，Mars全球测量师Mars Orbiter相机和其他THEMIS可见图像进行比较，以排除任何不明确的地质特征。在五个单独的图像中发现了八个清晰的尘鬼实例，其中有相当数量的未经证实的可能的魔鬼。据信，观测到的尘埃稀有性是由于在中等分辨率的THEMIS数据中难以识别尘埃和火星奥德赛轨道飞越当地时间晚于下午，而不是粉尘恶魔搜索的最佳时间。与地球相比，尘埃魔鬼活动的时间分布似乎在下午晚些时候加权得更多，但这可能是由于随溶胶时间的大小变化，溶胶后期的覆盖率较大或数量较少而引起的采样效应。红外热图像表明色谱柱中堆积的粉尘比周围表面凉爽，并且必须与粉尘恶魔中的气氛保持平衡。该能量传递估计约为可用来驱动系统的热通量能量的10％。由于减少了日光照射，粉尘柱遮蔽的地面也比周围环境冷。从可见波长图像中，粉尘柱的阴影被用来估计柱的不透明度，这反过来又给出了粉尘负荷的估计，其范围从1.9×10-5至1.5×10-4 kg·m-3，类似于基于登陆器的观测。没有热或可见的痕迹与尘埃相关联，表明在魔鬼通过后表面很快达到平衡，并且作为尘魔调查技术的轨道计数必须低估了尘魔的人口，因此低估了尘埃的装载量，从而确认了先前的工作。

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