Yep. The list of things that could make Earth a worse place to live than Mars is very short. A big enough asteroid to liquefy the entire crust would do it, for

Yep. The list of things that could make Earth a worse place to live than Mars is very short. A big enough asteroid to liquefy the entire crust would do it, for a while. A "mere" dinosaur-killer wouldn't be enough. Nor would nuclear war. Most of the rest of the options are still sci-fi, like Grey Goo events, or a very contagious very deadly infectious disease (and that would have to have some way of sticking around for a long time, for an orbital habitat or sealed earthbound habitat not to still be better than Mars, since you could get back more easily once it was gone or we had a way to fight it). Otherwise you've gotta start stacking disasters to get close, and even then it's pretty difficult. Mars is really bad.