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A. P. Zent (NASA Ames Research Center), J. Howard, R. C. Quinn (SETI Institute/NASA Ames)
Numerical models of the martian boundary layer assume instantaneous equilibration between the adsorbed phases in the martian subsurface and the surrounding pore gas. This assumption may not be valid for smectite clays. Smectites have interlayer sites that are accessible to H2O molecules during adsorption; filling these interlayer sites causes the swelling evident in smectites. The fundamental issue is the ease with which fully dehydrated clays, which have suffered collapse of their interlayer structure, can rehydrate. It requires, only a few percent of smectite in the soil mineral mixture to dominate the H2O adsorptive behavior of the regolith. That amount of clay is still allowed by available constraints, and some interpretations of the Viking biology experiments have invoked small amounts of these clays. We are exploring the kinetics of smectite adsorptive equilibriium experimentally. Samples will be pre-conditioned by baking out under vacuum for 24 hours. Other sample will be used as is, directly from laboratory conditions. If interlayer collapse inhibitea rehydration, then the samples will have markedly different adsorptive coverages after exposure to simulated Mars environment. We will report results of these experiments, and implications for the utility of numerical models that assume instantaneous equilibration. This research was funded by NASA Planetary Geology, RTOP 344-30-11-02
The author(s) of this abstract have provided an email address for comments about the abstract: azent@mail.arc.nasa.gov