http://en.wikipedia.org/wiki/Generation_ship http://en.wikipedia.org/wiki/Generation_ship The end goal of the generation ship would be to colonize a planet in

http://en.wikipedia.org/wiki/Generation_ship http://en.wikipedia.org/wiki/Generation_ship The end goal of the generation ship would be to colonize a planet in a far flung solar system. I would imagine that with the number of planets in existence, we could find one that was more hospitable than mars. This would also provide a more robust 'backup' for our species, in the case that the extinction event was solar system wide. Once again, I think Mars is a good stepping stone (for reasons that you mention), but I also imagine that a lot of the technology that would allow us to establish a sustainable colony on Mars would also allow us to develop robust generation ships.