alt Hacker NewsTo your first point: yes, that's the whole idea and it's been the same playbook for any colony from the Americas to Australia. Mars is a much bigger challenge but our technology has advanced enough to make this possible. Let those who would dare risk their lives to achieve something great do so. If you don't want to participate then you don't have to, this isn't a national or international project so you can safely sit it out.
To your second: there are calamities for which a second self-sufficient planet would be necessary. A large asteroid impact would utterly wreck the global industrial base which is highly dependent on international trade and specialization of resource extraction and manufacturing in different regions of the world, having an independent backup on a different planet is one of the few ways to hedge against this. You could argue that every country on earth be fully self-sufficient and then maybe they could survive but that seems like a much bigger task since you'd be building multiple completely independent civilizations instead of just one. Guarding against another global pandemic is another and being out of range of nuclear weapons and their fallout is a third.
The point on the first is the offworld colony is not a backup if it cannot be self sufficient and requires critical materials from Earth. Colonies like Australia also weren't meant or built to be self sufficient, they were extractive, extending the military reach of the British Empire and bringing in resources to make it rich. If the goal is a "backup" civilization it needs to be self sufficient for a long period to allow it to "restore" to Earth...
> A large asteroid impact would utterly wreck the global industrial base which is highly dependent on international trade and specialization of resource extraction and manufacturing in different regions of the world
That's economic collapse not extinction level collapse, space based mining might help with that but it's not the kind of event that actually makes a self sufficient
> Guarding against another global pandemic is another
This kind of presumes a very low level of travel and trade between Earth and Elsewhere which is extremely unlikely per problem 1 and the fact they'll need some economic reason to exist, at the very least they'll have to make money to buy the necessary items from Earth they cannot produce locally.
> being out of range of nuclear weapons and their fallout is a third.
This goes back to the actual thing I was talking about even a heavily bombed out Earth is hundreds of times easier to survive on than Mars or any given asteroid. Hence any tech that makes those places survivable make even the most damaged Earth also survivable.