While studying soils near Aeolis Palus in the Gale Crater, 'Curiosity' sampled part of what appeared to be an "alluvian fan" area. An alluvian fan is that area where a stream 'fans' out over a wider area. Generally, on Earth, alluvian fans have deposited pebbles and similar rocks in a pattern.
Below is a comparative picture showing the river bed alluvial fan section on Mars & one from Earth. The findings from the rover confirm that about 2% of the planet is water, which is incredible!
The pic above shows pebbles deposited from a once active stream, Mars (left) & Earth (right).
There was once water on Mars! Not just water, but flowing streams of water! This brings the theory that life existed on mars in eons past into new light, wouldn't you say? What would Edgar Rice Burroughs would be thinking right now, if he were alive?!
This, to me, is an incredible discovery! This is right up there with the newly discovered extra-solar planets! Keep watching the NASA website for new information regarding this discovery!