> A planetary extinction-level event has already happened where every land animal larger than 25kg died. Maybe it won't happen for another 65 million years. May

> A planetary extinction-level event has already happened where every land animal larger than 25kg died. Maybe it won't happen for another 65 million years. Maybe it will happen tomorrow. Maybe there will be a massive gamma ray burst that will sterilize the entire solar system. Who knows? Right, but... Mars is already worse for human life than Earth after every major extinction event. That's like "in case my house catches fire, I'm gonna build a backup house inside a working industrial furnace". If what we're worried about is surviving an event like the several that have affected Earth in the history of life on the planet, Mars is both more expensive and worse than a bunch of other options, including other space-based options (though I think that whole class of solutions is really wasteful compared to boring, Earthbound alternatives). That's a bad reason for going to Mars, is all I'm saying. I'll still be cheering along when the first boot-print is made, mind you. OK, here: strip Earth of all oxygen and its ozone layer and turn all the land into parched deserts that can barely support even the hardiest of plants. You want to wake up in a sealed shelter on Earth, or on Mars, after that happens? The smart answer is "on Earth" because the list of horrible things about your situation on Mars is still 5x that long, plus all those things are already problems there. Mars is very, very, very bad.