"Now that we're down on the ground with Curiosity we can see the textural evidence, the individual pebbles, the rounding that gives us a sense of that," he said. "It wasn't a single burst of water that ran down the canyon all in a day. There are too many things that point away from that. How long would it take? This is opening the door to answering that question."

Grotzinger said the discovery signifies the real beginning of the rover's science mission.

Now that scientists have proof that water once flowed across Mars, they can begin to look for signs of other elements, such as carbon, that are also needed to support life.

"Now we look at more rocks," said Grotzinger. "We get more context. We need to recreate the environment with even greater detail, with an understanding of the chemistry going on at that time, to understand if this was an area where an organism once lived. Was this an inhabitable environment? That is still to be determined."

Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at , on or subscribe to . Her email address is .