Well there's frozen water on the icecaps, and mars has an atmosphere. So it's possible that it once had life. A lot of people think that Mars used to have life
It’s volcanoes. The big one is Olympus mons. And that isn’t a scar, it’s Valles Marinaris (Or Mariner Valley), believed to be formed by erosion. It’s like the Grand Canyon, but the width of the United States.