It's not on ly water, European, American, and Russian probes already found good evidence of water.
And it's pretty much agreed that water is frozen at the poles.
What's exciting is that while there is physical evidence of water, this is the first very strong chemical, as opposed to physical, evidence, almost a smoking gun of liquid water on Mars. Not now but once, and for a long enough time for the chemical processes to occur. From hematite (which is usually an indicator of water, it can form w/o water but it is rare), to the "blueberries" which, if I recall the article, a chemist or a geologist can jump in now, are formed by processes involveing water, to the fact that a lot of the iron is sulfated, and also a fair amount of salts were found, pretty much means that liquid water pretty much had to have been there to form the minerals. THe headline on CNN said Mars was soaking wet. Maybe hyperbole, but that I think is the salient WOW that is this story.
I may be ugly. I may be an American. But don't call me an ugly American.