Theoretical Study of the Thermal Histories of Comets and Parent Bodies of Meterorites

通过对彗星和陨石母体的起源和热历史的研究，得到了以下结果：1.得到了一个新的彗核在奥尔特云中停留的热历史模型，该模型特别考虑了无定形冰极低的导热系数。从理论上推导了无定形冰凝结和保存的条件。在此基础上，对空间冰的结晶度进行了讨论。用质子束辐照不同成分的模拟宇宙冰，研究了有机物质的形成。导出了颗粒集合体的抗拉强度，并将其应用于Shoemaker-Levy 9.5彗星的劈裂。还对结果1至4进行了如下研究：柯伊伯带天体的起源，刚玉颗粒红外吸收系数的测量，以及星际暗云中H_2O和CO冰的红外天文研究。其中一些结果已作为一系列讲座于1994年6月在伊莱斯举行的国际宇宙尘埃联系暑期学校上发表。

The study of the origins and thermal histories of comets and parent bodies of meterorites leads to the following results :1. A new model of the thermal history of cometary nuclei during residence in the Oort cloud has been obtained, in which particular attention has been paid to the extremely low thermal conductivity of amorphous ice is taken into account.2. Conditions for condensation and preservation of amorphous ice have been theoretically derived. Crystallinity of ices in space has been discussed on the basis of the results.3. Formation of organic materials has been studied by irradiating proton beams on simulated cosmic ices of various composition.4. A tensile strength of grain aggregates has been derived, and the results have been applied to the splitting of comet Shoemaker-Levy 9.5. The following study has also been done in relation to the results 1 to 4 : the origin of the Kuiper-belt objects, mesurements of infrared absorption coefficients of corundum grains, and infrared astronomical study of H_2O and CO ices in interstellar dark clouds.Some of the results have been presented as a series of lectures at the International Summer School on Cosmic Dust Connection held at Erice in June 1994.