Effects of dust layers on thermal emission from airless bodies
Effects of dust layers on thermal emission from airless bodies
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DOI：
10.1186/s40645-019-0291-0
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发表时间：
2019-07-08
影响因子：
3.9
通讯作者：
Arai, Takehiko
中科院分区：
文献类型：
--
作者：
Biele, Jens;Kuehrt, Ekkehard;Arai, Takehiko
我们研究了薄的热不透明粉尘层对岩石和风化层热发射的影响，并确定了这些粉尘覆盖表面对日日照周期的热响应。对隼鸟2号的目标小行星（162173）龙宫的结果进行了计算，并通过轨道飞行器上和原位的热红外仪器进行了观测。我们表明，即使是非常薄的(10…100 μ m)细粒多孔粉尘层的热惯量为25Jm(-2)K(-1)s(-1/2)，可对表面温度产生显著影响，并使下垫材料在均匀半空间简化假设下的表观热惯量改变20%以上。底层材料的掩蔽在约1日皮肤深度完成，对应于Ryugu上的10mm。在0.1和1日皮肤深度之间，我们发现热滞后小于仅由尘埃组成的表面的预测。如果在“龙宫”上有尘埃覆盖，这应该在轨道飞行器的热红外成像仪（TIR）和MASCOT着陆器的辐射计（MARA）返回的数据中清晰可见，后者在着陆点观察到一个巨石。然而，事实似乎并非如此，尘埃似乎在小行星的热辐射中起着次要作用。
We have investigated the influence of thin thermally opaque dust layers on the thermal emission of rocks and regolith and determined the thermal response of these dust-covered surfaces to diurnal insolation cycles. Results are computed for Hayabusa2's target asteroid (162173) Ryugu, which was observed by thermal infrared instruments on the orbiter and in situ. We show that even a very thin (10..100 mu m) fine-grained porous dust layer with thermal inertia of 25Jm(-2)K(-1)s(-1/2) can have a significant influence on surface temperatures and alter the apparent thermal inertia of the underlying material derived under the simplified assumption of a homogenous half space by more than 20%. The masking of the underlying material is complete at about 1 diurnal skin depth, corresponding to 10mm on Ryugu. Between 0.1 and 1 diurnal skin depths, we find a thermal lag smaller than what would be predicted for a surface consisting of dust only.If a dust cover were present on Ryugu, this should be clearly visible in the data returned by the orbiter's thermal infrared imager (TIR) and the MASCOT lander's radiometer (MARA), which observed a single boulder at the landing site. However, this appears not to be the case, and dust seems to play a minor role in the thermal emission from the asteroid.