The World That Never Was - A nice HD video about the evolution of Mars and all Martian exploration missions. It also explores the question if life has once been abundant on the red planet, and where life may still be found today.
Did Mars long ago develop far enough for life to arise? If so, does anything still live within Mars’ dusty plains, beneath its ice caps, or somewhere underground? In 1964 the Mariner Four spacecraft flew by Mars and got a good look. What it saw looked more like the Moon than the Earth. Then, in the mid-1970’s, two lander-orbiter robot teams, named Viking, went in for an even closer look. The landers tested the soil for the chemical residues of life.