Gas Trapping in Ice and Its Release upon Warming

摘要

NASA's Deep Impact was a turning point in our measurements of comet properties. For the first time we obtained direct measurements of the density, thermal inertia of the surface, and, most importantly, the tensile strength of the upper layers. The very small tensile strength of only 1-10 kPa (like that of Talcum powder) tells us that comet Tempel 1 is a loose agglomerate of fluffy ice particles (Bar-Nun et al. 2007). In what follows, we describe how gases are trapped in fluffy ice particles, how they are released from them when the temperature is increased, either by overall heating or by pulsed infrared laser irradiation and finally, what happens when deeper layers release their trapped gases when the heat wave penetrates inward. In addition, it will be shown that laboratory measurements can now be carried out that address fundamental transport issues such as the release of trapped gases in such ice environments and their transport through thin and thick ice layers.