The curiosity rover belonging to NASA has explored in detail the Galer Crater on Mars. Recently, the rover has shown some evidence pertaining to a massive lake which might have been there in the past. The data that Curiosity showed suggested that the planet was having much more water in the past than it was thought to be.
The hypothesis behind the formation of crater is that it was a build-up of sediment over a long period of time. A huge mountain was there once at the heart of the crater. The scientists also suggest that there are possibilities of the presence of life on Mars when the lake existed.