Elon Musk says we must put a million people on Mars if the human species has a chance to survive.
This is a bad idea. Because if you think you have an escape hatch, what's the incentive to make it work here on the only planet that humans inhabit, or can inhabit, that we know of. Mars is a hail mary play. I think it's nice to have that as a dream, but it's not a viable plan.
Who would get to go? Donald Trump and his followers? What about Muslims? Get a panel of science fiction authors to tell you about all the problems with choosing a million people to be the survivors while the rest of us perish on the planet we destroyed.
Another question. Why won't we destroy Mars too? Isn't the more difficult problem figuring out how to live and grow in a way that does not consume our home? What if we destroy Mars too? Where do we go then?
PS: I am in favor of space exploration If you see a contradiction between that and the ideas expressed above I suggest: 1. You read it again. 2. Think some more.
By this logic, we shouldn't even try. That guarantees that the human race will cease to exist at some point, whether we cause it or not. Allowing a social safety valve is a human imperative. Humans for as long as we have been human have had groups strike out on their own to found new settlements, colonize new continents, and explore new frontiers. Your logic says that unless we can meet all sorts of preexisting criteria (fixing stuff here -- not a certain thing, deciding who gets to go, etc.) we shouldn't do it. Yours is ultimately a false choice, since going to Mars will mean developing innumerable technologies that will likely be able to solve problems here. It's not either or and it's ignoring the past (look at the benefits of going to the moon) to assume it is.
The Mars play isn't for the reasons we can think of that would involve us destroying ourselves. It's for all the reasons we can't think of that the universe will do it for us, like ants under a boot.
Then we're fucked. Better enjoy life now! :-)
What about an asteroid?
Still, it would be better for the human race to continue in any one of those cases than for it to die out. You seem to be saying it's better if humans cease to exist in the case of a catastrophe rather than only potentially people you don't agree with continuing to exist. That's just silly.
We have a better chance here. Mine the oceans. Send robots into outer space.