Open AccessH 2 O adsorption on smectites: Application to the diurnal variation of H 2 O in the Martian atmosphere
Author(s) -
Zent Aaron P.,
Howard D. Jeanie,
Quinn Richard C.
Publication year - 2001
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000je001394
Subject(s) - martian , adsorption , atmosphere of mars , montmorillonite , mars exploration program , regolith , atmosphere (unit) , diurnal temperature variation , astrobiology , clay minerals , geology , atmospheric sciences , chemistry , astrophysics , mineralogy , environmental science , thermodynamics , physics , organic chemistry
Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H 2 O adsorption kinetics on SWy‐1, a Na‐rich montmorillonite from Wyoming. The highest‐temperature (273 K) data equilibrate rapidly. Data gathered at realistic H 2 O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars‐like conditions we show that the interlayer sites of smectites are likely to be unavailable.