A critical unknown is how life originated on Earth. Was it seeded from elsewhere, or did it generate spontaneously from indigenous nutrients? The current vogue is the belief system that life will evolve on a planet with water, carbon dioxide, and warmth, given a few hundred million years. Scientists of that persuasion developed the basis for exploration by NASA. Since early Mars apparently met that criterion, the Mars Exploration Program was formulated as a search for early life on Mars. All of the orbiters and robotic landers on Mars were designed with a principal goal of finding evidence of early life on Mars. So far, no evidence has been found, and there are good reasons to think that it is extremely unlikely that evidence of early life on Mars will ever be detected. Enthusiasts have invented a wide variety of justifications for why we should send humans to Mars. In reality, it seems that the real reason to send humans to Mars is that it is the next logical step beyond the Moon, and you have to send humans somewhere. Nevertheless, a human mission to Mars would be a great engineering achievement, and it would be the ultimate culmination of 60+ years of rocketry and space exploitation.