彗星核的热阴影和成分结构
Thermal Shadows and Compositional Structure in Comet Nuclei
摘要：
我们使用一个完全三维的热演化模型来研究一个不均匀的表面热结构的彗星上的影响。表面的热斑会投射出“热阴影”，具有很强的横向热梯度。相应的成分梯度可能很强，特别是如果在最热的地区触发无定形水冰的结晶。结果表明，该结构的空间范围主要取决于折射率、热导率和日心距。在某些情况下，由地表特征的热阴影引起的地下结构可以维持超过1000万年，这是从柯伊伯带到内太阳系的平均传输时间。不均匀的成分结构可能是演化的产物，并不一定意味着彗星是由积累在原行星盘不同区域的积木组成的。
英文摘要：
We use a fully 3-dimensional thermal evolution model to examine the effects of a non-uniform surface albedo on the subsurface thermal structure of comets. Surface albedo markings cast "thermal shadows", with strong lateral thermal gradients. Corresponding compositional gradients can be strong, especially if the crystallization of amorphous water ice is triggered in the hottest regions. We show that the spatial extent of the structure depends mainly on the obliquity, ther- mal conductivity and heliocentric distance. In some circumstances, subsurface structure caused by the thermal shadows of surface features can be maintained for more than 10 Myr, the median transport time from the Kuiper Belt to the inner solar system. Non-uniform compositional structure can be an evolutionary product and does not necessarily imply that comets consist of building blocks accumulated in different regions of the protoplanetary disk.
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