Using a drop experiment facility, Marangoni convection induced by a temperature gradient in a 7.35wt% NaCl aqueous solution was observed in situ under microgravity in order to reveal Marangoni effects on the crystallization from aqueous solution in a spaceship. In the drop experiment, after microgravity was achieved, the buoyant convection diminished completely within 1.0s. Since the flow rate became quite steady after 1.0s of microgravity, this was regarded as the flow rate of Marangoni convection. The flow rates of Marangoni convection were also measured as a function of the exposure time of the solution surface to the surrounding air. The flow rate decreased exponentially with an increase in the exposure time. This decrease could be explained by a model containing Langmuir type adsorption of the air on the solution surface. Our result suggests that the solution surface would be entirely contaminated by the adsorbed gas molecules within several hours, and Marangoni convection would diminish.
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