Curiosity Finds Evidence of Rivers on MarsThe Curiosity rover has already managed to make a big discovery: a river on mars that was "somewhere between ankle and hip deep." While we had plenty of evidence that water did flow on the planet's surface, to find a record of it being so vigorous and deep so quickly speaks to a truly wet history for the planet.
The evidence comes from some deposits that Curiosity studied, which closely resemble river rocks on Earth. The stone is a conglomerate formed when rounded rocks are deposited on the bottom of a river and cemented together. As JPL's statement explains via a quote from Berkeley scientist William Dietrich, "From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep." That is actually quite fast, and would be a major creek here on earth.
The Gale Crater seems to have been the site of a lot of water flow. The stream leads back to a break in the crater's wall, and even forms an alluvial fan(see: Wikipedia) near the base.
Curiosity should be able to learn something about what the water on Mars was like, thanks to the conglomerate. The mortar used to hold the rock together will differ depending on different watery conditions. The trick, then, is to look closely at it.
JPL isn't expecting to find any evidence of biological life in the rocky outcropping. They don't believe that it is a good candidate for it. But the rover will be roving over to Mount Sharp later in the mission, which is deemed the most likely spot for biological specimens to be. And, as Caltech scientist John Grotzinger notes, this is evidence that Curiosity has found a potential habitable spot.