The problem with this argument is that it is a false choice. We do not need to choose between fixing our planet and expanding into space. There are seven billion of us, and collectively we’re not that bad at multitasking.

Furthermore, it is a straw man, because nobody actually believes that we should give up on Earth. You cited a number of headlines attributing this position to people like Elon Musk and Steven Hawking, when a quick reading of their actual quotes shows that they do not actually say what the headlines claim (Musk also runs a clean energy company for Pete’s sake—doesn’t sound like he wants to give up on Earth). I really want to believe that you wrote your article in good faith, but that means I must believe you did not read the articles you linked as evidence.

Fixing problems on Earth vs colonising Mars is the difference between carefully maintaining your family PC and buying a second one so you still have a working one when the first one breaks down.

Redundancy doesn't fix problems but it cushions the failure case. There are numerous ways Earth could be wiped out in a way we can't defend against.

I see this phenomenon quite a lot, even on HN. Supposing we find a planet that is conducive to life, how can we avoid exporting all of humanity's cultural and biological baggage to that new civilization? Aside from the exploitation and near-genocide that took place in the Western hemisphere, how is it really any different that the opening up of those continents, but with a bigger ocean between? I've seen other discussions try to route around this question by talking about Mars or some other hostile environment as perfect for the type of co-operative commune they imagine humanity could be, one where people must rely on each other or die. I don't see a qualitative difference between that environment and the deserts of the American West, where the climate was harsh and water scarce.

Those migrations didn't bring utopia, either to the participants or the rest of humanity.

I agree that utopian predictions have a long history of failure and should be taken with a Mars-sized grain of salt. However, I would argue that the difference is that there is not likely to be complex life on Mars or any other location in our solar system. This makes it quite a bit different from the North American example, in which immense suffering was inflicted upon the existing inhabitants of the region. If any planet or moon was found to contain life-forms capable of experiencing suffering, I and (hopefully) most people would be against human settlement there.