[nightdriver]

"Under the surface, sealed from the partial vacuum they laughingly call an atmosphere, ice would be present and would sublimate off only where the ice were exposed by erosion of the surface."

Subsurface water is a possibility, but that doesn't lend much credence to all that raging, copious flow of water that the NASA types are proposing.

After all, remember "polywater?" It was found in the tiny interstitial faults in the quartz moonrocks. Water like that may be found on Mars, but it will most likely be of many orders of magnitude less in quantity than the raging torrents imagined by these guys from NASA.

[RightWhale]

Here in central Alaska it is semi-arid. It would be a desert except that the ground is frozen. The ground on Mars has a lot of the same look, so if they find permafrost there it wouldn't be a surprise. When they drill down they might expect to find ice, and it would probably be reasonably pure and free of mineral contaminants, not brine. Ice tends to work out contaminants, purifies itself.