This is the clearest image of Mars snapped by the first successful mission, Mariner 4, which flew past the Red Planet on July 14, 1965, beginning six decades of Mars exploration. The craft took 21 pictures of Mars, covering only a tiny fraction of the surface. The region it scanned contained mainly craters and volcanic plains, which none of the mountains, canyons, or dune fields revealed by later missions. [NASA]
Find out more in our radio program entitled Six Decades.