We know that Mars has formations indicating the brief, localized presence of liquid water. Probably these are due to impacts, which melt subsurface ice and produce a temporary microclimate made up of water vapor, making liquid water possible. This best explains the from-nowhere-to-nowhere patterns of all the known channels.
A temporary atmosphere of water vapor? I don’t know if that’s possible or not. But the general consensus is that Mars was briefly more earthlike in the distant past before the core solidified. It makes sense that all the inner planets had atmospheres at one time, even Mercury, before the solar wind blew them away. What remains now are mostly heavy rocky materials which originally were only trace elements.