[jcranmer]

> I don't see why this realization should be regarded as a counter argument to establishing a Mars colony. It's really really hard and a lot of problems need to be solved.

The point is that, right now in 2019, we do not know how to build a self-sustaining colony outside of Earth's biosphere. If you want such a thing to exist, you have to do a lot of research first to enable it. But, in general, the space enthusiast crowd isn't interested in pushing for that kind of research. And without that research, a lot of the arguments for space travel are very moot.

[spacenick88]

I'm such a space enthusiast and I'd absolutely love a Biodome 3. That said, I think that people tend to confuse "sustainable colony" and "self-sustaining colony". If it ever comes to it, we will have a sustained presence on Mars for decades before it becomes self-sustaining. That said even with supplies from Earth a Mars base will need a lot of sustainability tech that can be applied on earth too.