Lincsbear saidAn amazing discovery!
Apparently, the salts dissolved in the water lowered its freezing point so much it could flow on the surface, even in Mars` frigid summers.
Well, yes, but that factoid has more to do with one of the arm-wavey explanations for where the putative water might be coming from.
Temperature is not the problem here. In these equatorial sites, the temperature gets well above the freezing point in summer. But the pressure is so low that water would only be stable as a gas. (No problem... water is only stable as a gas in your kitchen, too. If you leave a glass of water out, it will disappear into the atmosphere!)
But. There is no evidence that water flows
, only that it is there. No theory about the source of water explains all of the data. And there just isn't enough data to sort out the different theories.
The bit about the brines is that the salt might get hydrated from atmospheric moisture (dew). But there is no data about the humidity, so the feasibility is unknown. In this case, the salts deliquesce, and "sweat out" the water as saturated brines. This happens at a couple of very dry places on Earth. But nothing that we know of can live in brines like that.
If you walk around the tailings of a desert copper mine, you can see all sorts of mineral crystal flowers forming around your footprints, from chemical reactions that happen in the morning dew. These are the same sorts of minerals that appear to be abundant on Mars, in places that once had water. (On Earth, these build up all summer, then get washed away in the first rains of Autumn.) Lots still unknown about this!
A more interesting possibility is that deep aquifers might transport the water to the surface through faults. Water might briefly exist as liquid because the pores in the rock or soil provide pressure through capillary forces. The salts would form because the water carries them to the surface, then evaporates, leaving the salts behind, so that they become concentrated at the surface. Living organisms might exist lower down in the system. Even better, these salts could eventually get buried into the liquid water zone. Since they are highly oxidized, and the bedrock is highly reduced, this would set up a source of potential energy that microbes could live on.
There are a couple of more theories, of a TLDR sort. But in the end, there just isn't data to support any of them. Yet.