I'm not arguing for underwater cities or against going to Mars. I'm just saying that the cost and effort of getting everything to Mars is the easy part, and is not the part that will actually ensure humanity's survival.

Exactly right, how this escapes people I am unsure. The absolute worst climate predictions, asteroid impacts or seismic events wouldn't be nearly as hard to recover from than trying to get to and then live for a single day on Mars.

Fifty years of successful Martian colonization would be a good start towards self-sufficiency on that planet.

These are successful, by at least some definitions, but are not self-sufficient. Why are you more optimistic about a Mars colony than our experience with places on Earth which are much less inaccessible and more inhabitable might suggest?

If future Mars missions are launched with the goals of establishing a research station, then yeah, I don't expect it to become self-sufficient.

But, if future Mars missions are launched with the expressed goal of establishing an independent colony, then I think there's at least a chance it might work.

Certainly there are a lot of challenges. We probably don't even know what all of the challenges are yet. For all we know, Mars could be host to a deadly microorganism, some extremophile we've never seen before. It could go the way of the Roanoke colony, with a total loss of the whole colony.

I would still go anyway though. Because maybe, after fifty years of chipping away at it, we would have learned enough and developed enough new technology as a result of the effort to have made it all worthwhile.

It is a huge risk for a potentially huge payoff. I'm always amazed when HN, of all places, doesn't see it that way.

If Chile or Argentina could find a way to practicably expand their settlement on the continent, rather than subsidize it like they do now, then they likely would. That they haven't suggests they haven't figured out how.

In any case, Tristan da Cunha is in a much more hospitable area, but its self-sufficiency is shaky. One fire, for example, can ruin their economy and require external support.

I'm amazed that you think it requires an attempt at permanent colonization of Mars in order to get the benefits, when we would get the same benefits here on Earth, should we try to have a permanent, self-sufficient colony on Antarctica, Greenland, Alaska, or Nunavut, with lower risks.

Maybe you can even suggest it to Musk. "Mr. Musk, I disagree that Mars is exciting. Please stop building rockets, and start looking into colonizing something safer here on Earth. Thank you."

People climb Everest because it's their dream, because the intangibles are worth the tens of thousands of dollars to them. Chile and Argentina subsidize their colonies on Antarctica because of dreams of land.

But even Denmark hasn't figured out how to make Greenland profitable. It continues to subsidize life on that island. That's about 60,000 people who would love to be self-sufficient. Is the problem only that they are insufficiently excited? Or that there aren't enough people there? How many more do you need?

http://en.wikipedia.org/wiki/Giant_impact_hypothesis

"collision between the Earth and an astronomical body the size of Mars"

The first step would be a colony that can produce and clean its own air and water and some of its food. This seem achievable in the near term. The second step is a full ecosystem (needs almost no nutrients from earth), which is much harder but I think biosphere 2 is a good proof of concept. Mars is much colder with less sunlight so it is a much harder problem on Mars. The finial step is an independent industrial base. You mentioned medicine, but I'm more concerned with the microprocessors to keep the automation running. Humanity can survive without medicine, and with a few easy things like penicillin we can do quite well (we can also avoid bringing the majority of diseases to Mars in the first place). Without automation I don't think one person can produce enough resource to sustain themselves in such a hostile environment.

Self-sufficiency is hard and I think a million people is a good estimation of how large a Mars colony would be before it became truly self sufficient.

The issues with getting something like an ecosystem on Mars would be much more dramatic, esp. given that while there are some ways of getting O2 and carbon, there isn't a source of nitrogen on Mars that we know (we assume there's fixed nitrogen in minerals, though that's very hard to breathe). Any loss of significant life forms would need to be replenished from Earth. And while some life forms will probably manage in 38% gravity, there's no reason to assume many would have long term viability (especially vertebrates like humans who depend on Earth gravity to function).

Getting an ecosystem on Mars that could support humans doesn't seem like it's in the realm of possibility to me, especially when there's good reason to believe humans themselves wouldn't be able to survive for long periods there unless something managed to solve that very hard problem. You could use a centrifuge for the long trip out (and nobody could survive without that), but you can't just live in a centrifuge on Mars forever.