[defrost]

I have some grasp of travel having working in global scale geophysical exploration and mapping and having visited a majority of the 190+ countries as a result.

The journeys described by dukeyukey as part of the spread of humanity across the globe took place over many many generations in short stages.

The longer journeys you describe all occurred in or post the European age of Expoloration.

Columbus had an idea of how long it would take to reach the Dutch East Indies, it was based on an incorrect idea of the radius of the earth.

Reid Stowe's 1,152 days at sea "without resupply or stepping on land" wasn't quite a voyage to Mars - fresh water condensed and was collectable, fish swam by and could be eaten, his pregnant co-sailer got off the boat after 306 days .. and the journey was possible without propulsion, fuel, and a massive radiation sheild.

I'm not saying that Mars is impossible, I am stating that no comparable journey has been undertaken by man .. the journeys by Europeans across the globe were journeys from where humans lived to other places where humans also already lived across oceans that supported life.