Donald Stanley Musselwhite

Liquid CO2 breakout and the formation of recent small gullies on Mars

We show that the action of a CO2 suspended flow could have produced the recent small gullies on Mars, and, hence, that liquid water is not required. The model involves the build-up of a liquid-CO2 aquifer behind and below a dry-ice barrier (dam/cap rock) in the pore spaces a few meters into the rock from the cliff face and on order of a hundred meters below the top of the cliff brink surface. Seasonal (or obliquity-cycle-seasonal) heating causes pinching out of the dry-ice barrier and rapid release of the liquid CO2. Erosion of the gullies occurs as the rapid vaporization of the liquid CO2 with entrainment of rock and clathrate-hydrate ice produces a density flow analogous to a terrestrial nue ardente.

Alteration of volatile inventories by polar clathrate formation on Mars

Recent models of chaotic variation in the Martian obliquity suggest that CO2 could be released during times of high obliquity and then recaptured in the polar caps as ice or clathrate during times of lower obliquity (Jakosky, et al., 1995). A natural implication of clathrate trapping is that other species in the Martian atmosphere, including noble gases, must incorporate in the water ice structure as well, in varying amounts according to the size and polarizability of the molecules as well as their atmospheric abundances. For nominal estimates of cap volume and amount of incorporated CO2 , we find that the current atmospheric inventory of noble gases is not representative of the bulk inventory in the Martian surface-atmosphere system. In particular, xenon and krypton are underrepresented in the present atmosphere. Models of source regions for Martian volatiles, which are constrained by noble gas abundances, must be modified to take these fractionation effects into account if indeed evidence for large amounts of polar clathrates is found.