Planetary Group Seminar: How important are clathratehydrates for planetary processes and in comets? (W. F. Kuhn)

Clathrate hydrates (gas hydrates) are commonly invoked to explain phenomena on andunder the surface of celestial bodies (planets and their moons as well ascomets), attempts which are largely based on thermodynamic modelling.What is rarely considered are the transformation kinetics involvingclathrate hydrates. We report here on laboratory studies of the formation anddecomposition kinetics of these clathrates, which put in question some of thespeculations about their role in planetary processes. We also show that adefective form of ice - usually labelled "cubic ice" - plays anunderestimated role in these processes. We shall emphasize the need for morelaboratory work in the temperature range below 180K to further elucidate theinteractions between small gases and solid forms of water ice in astrophysicalprocesses on celestial bodies.