The first real ‘direct’ observation of water:
“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.”
Apparently, it’s sedimentary conglomerate. Rounded rocks smoothed by water and deposited in a cement like structure, which is now jutting above the surface as it lays in a large alluvial fan bed. Comparison photo from Chile, back on Earth, of what appears to be a similar phenomenon. The Rover is still headed towards Glenelg.
Video comparison on alluvial fans between Las Vegas and L.A. and on Mars, where the Rover sits:
Thanks to everyone in the Jet Propulsion Laboratory living on Mars time!