This is very misleading -- we already know there's plenty of water on Mars, by way of several lines of evidence. The original observation of seasonal markings doesn't address the issue of water on Mars, for which there's plenty of evidence, but whether the markings result from water briefly flowing downhill as it sublimates (a process measured in seconds because of Mars' low atmospheric pressure), leaving a trail of debris to mark its passing -- a much less dramatic claim.
But these facts won't stop ignorant science journalists from presenting this observation as though it represent some kind of theoretical breakthrough.
Link: http://en.wikipedia.org/wiki/Water_on_Mars
Quote: "Water on Mars exists today almost exclusively as ice, with a small amount present in the atmosphere as vapour.[1] The only place where water ice is visible at the surface is at the north polar ice cap.[2] However, abundant water ice is also present beneath the permanent carbon dioxide ice cap at the Martian south pole and in the shallow subsurface at more temperate latitudes.[3][4][5][6] More than five million cubic kilometers of ice have been identified at or near the surface of modern Mars, enough to cover the whole planet to a depth of 35 meters.[7] Even more ice is likely to be locked away in the deep subsurface.[8]"
In other words, contrary to the linked article, the presence of water on Mars is not a new discovery.