Laboratory investigations of volatile trapping in comets

This research program consists of laboratory studies of the formation of ice at low temperatures to simulate the formation of comets in the outer solar nebula. The ice is condensed in the presence of various mixtures of gases at a given temperature, and then warmed to see at what temperatures the gases are released and how much gas was actually trapped. Our results to date indicate that the trapping of argon, krypton, and xenon in ice formed at approximately 50 K fractionates these gase in a way that fits the relative abundances found in the atmospheres of Mars and Earth. This is markedly different from the situation in chondritic meteorites, where the abundance of xenon is about equal to that of krypton. It appears that comets represent a better source for planetary volatiles than do the meteorites.