The lower atmospheric density (equivalent to 40 miles altitude over the Earth) means the vapor point of water is reached all the time; but the surface is so cold that the ices tied up deep in the soils will be able to stay put for a long time. Closer to the surface, the ices can go from frozen directly to vapor with a slight push (such as an impact from space).
My question related more specifically to the thought that man might be able to generate huge amounts of atmospheric gases. So my thought was would they stay around for a few years or a few millenia?