Alteration Processes of Cometary Theories on the Origin Examination of the assumptions

A key to testing the two theories

Crystalline structure of ice depends on the conditions at condensation and temperature of the ice after condensation. For instance, when H O vapor condenses on solid surface at low temperatures, amorphous ice is formed because adsorbed H O molecules cannot diffuse efficiently to proper sites for forming crystalline ice. At high temperatures, on the other hand, H O molecules quickly diffuse to form crystalline ice. In addition amorphous ice transforms to crystalline ice at a rate determined by the temperature of the ice. The time required for amorphous ice to transform to crystalline ice is quite long at low temperatures, but decreases rapidly with increasing temperature (see §8.4). At K, the transformation time is on the order of the solar system age of byr.

Those facts imply that the difference in the temperatures of cometary ice at condensation and thereafter in both models results in different crystalline structure of H O ice. The quenching model predicts the condensation temperature of H O ice to be K in the solar nebula and a higher temperature in the Jovian subnebula. In the interstellar-ice residue model, on the other hand, the ice has not experienced temperatures higher than K. Thus, crystalline ice is predicted by the quenching model, and amorphous ice by the interstellar-ice residue model. Crystallinity of cometary ice is a key to testing which of the quenching model and the interstellar-ice residue model is plausible.