So there is no spectral signature of either water or salts associated with these markings -- not yet anyway. (The hint was that something may have been found but can't be announced yet).

Salts are a problem as well because they would tend to "clog the plumbing" sooner rather than later.

However, all the indications are that a fluid is active at the surface in widespread locations for an extended period during the Mars year, and has been active for many years.

Water/brine? Could be, certainly. Could it be something else such as an aqueous solution of... something? Why not?

Remember when Nick Hoffman was speculating about the possibility of carbon dioxide flows? I've suggested sulfuric acid as a possibility because it seems to be a fairly common planetary volatile and would remain fluid at the temperatures and pressures under consideration. Water is certainly possible as well, but pure water is unlikely, whereas brines of various sorts have their own problems and limitations.

It would sure help if direct analysis were possible. In the meantime, it's nice to know that these markings are accepted as indications of fluid flows at the surface. Finally. After all these years!