Source - NASA Science News for Sept. 27, 2012
Curiosity has found evidence that a stream once ran vigorously across the area on Mars where the rover is now driving.
The complete article can be found here: http://science.nasa.gov/
Here is a quote from that article:
"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," said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. "Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it."