A dinosaur-killer sized asteroid strike would still leave earth far, far more habitable than mars is (there would at least be air and water) as would essentially any other conceivable natural or cosmic disaster.
I hadn't really thought about that before. But I still think the sudden, cataclysm still could render humans extinct on Earth even if Mars is a more difficult climate. Mars dwellers would have had a great deal of time to prepare for that environment. On Earth, it would be suddenly thrust upon them. This is also assuming that the Mars colony was at a point where it could exist without supplies from Earth.
I thought so too, until I read this New Yorker article [1].
It’s about a site in the Hell Creek formation that seems to show, in incredible detail, what happened in the first hour after the Chicxulub strike a couple thousand miles away.
It reset my ideas about Earth’s habitability after the impact.
