A unified model for evolution of the temperature, chemical composition, and mechanical strength of cometary nuclei is presented with taking account of relevant elementary processes such as release of net latent heat associated with the phase transitions of amorphous ice containing the volatile molecules and sintering of the icy grains in the nucleus. On the other hand, CO 2 condenses on the surfaces of the dust grains immediately after crystallization of amorphous H 2 O ice and is preserved. As the crystallization proceeds, sintering of CO 2 and H 2 O proceeds, and as a result the tensile strength is enhanced by three orders of magnitude. No CO 2 case, where CO is contained in considerable amount but the CO 2 abundance is small. H 2 O proceeds slowly, and consequently the gas pressure gradient due to CO overwhelms the tensile strength at some point, leading to disruption of the nucleus.
Discussion is given on the implications of the results.
It is pointed out that the diversity of evolution of cometary nuclei is related to the volatile composition of grains in the parent molecular clouds from which planetary systems form. The implications of the evolution of the tensile strength of cometary nuclei are discussed in connection with collisional accretion of icy planetesimals to the Jovian planets and outer solar system bodies. Welcome to GoLive CyberStudio Return to Colloquium Homepage . Return to Coll oquium Schedule . Return to List of Abstracts .