Mars is cold and dry, but billions of years ago, it was cold and wet. That's according to new evidence from NASA's Curiosity rover, which is currently exploring a large crater on Mars.
The rover has found geological evidence that lakes of liquid water existed in the crater 3.5 billion years ago. "The lakes may have existed for hundreds of thousands of years," says John Grotzinger, a researcher at Caltech and chief scientist for the rover.
