The molecular composition of comets and its interrelation with other small bodies of the Solar System
The molecular composition of comets and its interrelation with other small bodies of the Solar System
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彗星的分子组成及其与太阳系其他小天体的相互关系
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发表时间：
2006
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通讯作者：
J. Fernandez
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作者：
J. Fernandez
我们对彗星核组成的知识现状进行了回顾，并与我们对太阳系其他小天体——行星际尘埃、陨石、小行星、海王星外天体的组成的了解进行了比较。介绍了目前的实地分析和遥感调查方法。彗星是一种活跃的天体，它们将内部物质倾泻而出，形成一种尘埃大气，这种大气可以通过遥感进行调查。对于小行星和海王星外天体来说，情况并非如此，因为它们只能到达外表面。收集到的星际尘埃粒子和陨石可以在地面实验室里悠闲地进行分析，但我们不能肯定地知道哪些是它们的母体。对活动彗星的光谱观测已经取得了相当大的进展，主要是在红外和无线电波长。我们现在可能知道了彗星冰的大部分主要成分，但我们对次要成分的了解仍然非常有限。彗星尘埃颗粒的元素组成是通过原位调查得知的，但它们的化学性质只有像硅酸盐这样具有可观测光谱特征的物种才知道。晶粒中存在的高分子质量（半）难熔有机物质是一种关键成分，但仍未被充分表征。这个成分可能是昏迷中分子分布来源的原因。从彗星到彗星的组成有很大的差异，所以没有一个“典型的彗星”可以被定义。彗星的组成和形成区域以及它们随后的动力学历史之间还没有明确的联系。
The present status of our knowledge of the composition of cometary nuclei is reviewed and compared with what we know on the composition of other Solar System minor bodies — interplanetary dust, meteorites, asteroids, trans-Neptunian objects. The current methods of investigations — by both in situ analysis and remote sensing — are described. Comets are active objects pouring their internal material to form a dusty atmosphere which can be investigated by remote sensing. This is not the case for minor planets and trans-Neptunian objects for which only the outer surface is accessible. Collected interplanetary dust particles and meteorites can be analysed at leisure in terrestrial laboratories, but we do not know for certain which are their parent bodies. Considerable progresses have been made from spectroscopic observations of active comets, mainly at infrared and radio wavelengths. We probably know now most of the main components of cometary ices, but we still have a very partial view of the minor ones. The elemental composition of cometary dust particles is known from in situ investigations, but their chemical nature is only known for species like silicates which have observable spectral features. A crucial component, still ill-characterized, is the (semi-)refractory organic material of high molecular mass present in grains. This component is possibly responsible for distributed sources of molecules in the coma. A large diversity of composition from comet to comet is observed, so that no “typical comet” can be defined. No clear correlation between the composition and the region of formation of the comets and their subsequent dynamical history can yet be established.