Mars in the popular imagination is a planet that was once warm and wet, a place that might have fostered life. But new research shows how these imagined pleasant periods were brief, hellish, and punctuated by utter catastrophe. New and detailed computer modeling paints a picture of blankets of molten rock, scalding rain and colossal floods more than 3 billion years ago that rapidly and permanently scarred vast regions of the surface following crushing impacts from comets or asteroids.