Scientists have discovered never-before-seen impact “megabreccia” and a possibly once-habitable ancient lake on Mars at a place called Holden crater. Topping the clay layers that formed in the placid Holden crater lake are layers of great boulder-filled debris unleashed later, when water breached Holden crater rim, creating a torrential flood that eroded the older lake sediments. The body of water would have been larger than Lake Huron.