Why did we choose Gusev Crater? Ah because we think there used to be a lake there a long time ago. Gusev is a great big hole in the ground. It was caused by a meteorite impact on Mars billions of years ago. It's about a hundred miles across and there is a giant dried up river bed that flows into it. And we think that this river bed once allowed water to flow into the crater. It filled up sort of like a big bathtub and then the water drained away or evaporated away, but it would have left sediments. It would have left stuff behind and by looking at those materials maybe we can learn something about what it was like in that lake a long time ago.
Steve Squyres
Principal Investigator
Cornell University