Diversity and similarity of comets
Diversity and similarity of comets
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彗星的多样性和相似性
DOI：
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发表时间：
1987
期刊：
影响因子：
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通讯作者：
A. Delsemme
中科院分区：
文献类型：
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作者：
A. Delsemme
回顾了彗星从早期都是相似的阶段到后来的多样性的演变。所有原始彗星的元素丰度都可能是原始的，即所有元素的太阳丰度比，包括C，N，O，S，但H(假设是He和Ne)是严重贫化的。固相最初是非常细小的颗粒，通常为0.1微米或更小，最终烧结成更大的粒子团。挥发相含有冻结在颗粒团孔隙中的H、C、N、O和S分子；宇宙射线加上太阳辐射改变了地壳的挥发比和耐火比。尘埃尾巴、等离子体尾巴、新彗星和老彗星之间的测光差异，以及气相可变的碳耗竭，似乎都是由衰变过程引起的。
The evolution of comets from an early stage where they were all similar, to the later diversity is reviewed. The elemental abundances of all pristine comets are likely to be primitive, that is in solar abundance ratios for all elements including C, N, O, S, but with the exception of H (and assumedly He and Ne) that are severely depleted. The solid phase was originally in very fine grains, typically 0.1 micron or less, eventually sintered into larger grain clusters. The volatile phase contains H, C, N, O, and S molecules frozen in the pores of the grain clusters; cosmic ray plus solar irradiation changes the volatile to refractory ratio of the crust. Differences in dust tails, in plasma tails, in photometry between young and old comets, and in the variable carbon depletion of the gas phase seem to be induced by the decay processes.