Forty Years of Martian Chronicles: A Very Familiar Yet Alien World

Humans, viewing Mars from afar, have seen it transform from a Greco-Roman god of war, to Percival Lowel's early 20th century world inhabited by a dying canal-building civilization, to a barren cratered moon-like world through the eyes of its first orbiting visitor in 1964, Mariner 4. In 1976 all of that changed as the Viking 1 and 2 landers sent us the first images from the surface of another world, one both alien and yet eerily familiar. These landers examined Mars' mineralogy and geology, but at the center of their investigations was the search for organics and life. Even though by set criteria the results for life were positive, alongside the negative results for organics, the possibility for martian life on the surface became more unlikely. Twenty years later, Pathfinder piqued our interest and gave us a hint of what a roving robot might accomplish if allowed, followed in 2004 by two rovers, Opportunity and Spirit, that found a clearly written history of liquid water and reignited the possibility of past life. In 2008 the Phoenix lander confirmed frozen water, examined micron-sized dust particles, and by mixing water and martian soil, tasted the minerals of life. Now, Curiosity, the largest and most sophisticated science platform ever to explore Mars, promises to make even more amazing discoveries. We will look at the major past and on-going scientific discoveries and how they have altered our views of Mars, its history, geology, chemistry, its ability to support past, present, or future life, and finally, their impact on our view of life on Earth and our place in the universe.