They actually learned a bunch of things from that. Including that the concrete took CO2 from the atmosphere in chemical processes that was unexpected, leaving the plants short and not producing enough oxygen.

The insects and plants selected didn't cohabit well, as well another issues. There was clearly lots to learn from the experiment.

That only says it needs to be tried again. And again. Until it works.

Hear, hear. I can't for the life of me understand why that experiment isn't being tried hundreds of times, all over the world. Learning how to create sustainable sealed ecosystems is one of the most important things we can do. Quite apart from the valuable knowledge we'll gain, once we get that nailed we can seed those suckers all over the place - South Pole, Sahara, orbit, Mars, upper atmosphere of Venus...

The really weird thing is we already sort of know how - "bottle gardens" are a thing. It seems to be mainly a question of scale. So why aren't we building bigger and bigger bottle gardens?

>I can't for the life of me understand why that experiment isn't being tried hundreds of times, all over the world. Learning how to create sustainable sealed ecosystems is one of the most important things we can do.

Apparently, after giving it one little shot here in a convenient location and failing miserably, we think we can just skip straight to Mars and be successful there.

There are four additional experiments listed under this link:

https://en.wikipedia.org/wiki/Biosphere_2#See_also

So that's at least five.

In Poland, there's a Mars-like base being built right now, though not aimed at testing self-sufficient ecosystems but equipment and work procedures of potential off-world colonists. My guess is there's more of such little-known projects happening.

The point being, the number of projects related to living off-world is slowly increasing, and my guess it will only go up as the perspective of Mars mission comes closer (SpaceX is doing a lot of good work making this close to "very soon" in peoples' minds). So we're definitely not "giving it one little shot".

An experiment is only a failure if you don't learn anything from it.

>someone should go out there and try to set up a self-sustaining colony on the pole or in the middle of a desert.

>That's already been done. It was called "Biosphere II", set up in the Arizona desert. It failed.

>An experiment is only a failure if you don't learn anything from it.

It was a failure. Go back and look at what I replied to: the OP said someone should go set up a self-sustaining colony. That was attempted with Biosphere II. It failed. It was not self-sustaining.

It they learned stuff from it, that's all well and good, but it doesn't meet the requirement from the OP of being self-sustaining.

The OP says we should set up a self-sustaining colony on Earth as practice for something in space. We have not done that. We tried and we failed, and we didn't bother trying again. So the point here is: what makes us think we can set up a self-sustaining colony on Mars when we can't even set one up in Arizona? Cart before the horse.

You appear to be thinking of it as an attempt to set up a colony, whose purpose was to be a colony (or a simulation thereof). It failed at that, sure.

But it can also be thought of as an experiment whose purpose was to test the hypothesis "this is a good way to set up a colony". In the scientific sense of the term, experiments that disprove their hypothesis are as successful as those that prove it. A failed experiment is one that is inconclusive or incomplete.

You seem to be thinking of it as a scientific experiment. I'm not. In the context of the OP's comment, I'm thinking of it as a "trial run", to see if we can figure out how to build a self-sustaining colony here on Earth, where it's safe and we can cut the "simulation" short if there's a problem and try again, before we try it for real on another world. In that context, we failed. We did not set up a self-sustaining colony and prove that we can do such a thing successfully. Perhaps we could be successful if we tried it a few more times, but we have not been successful yet. Therefore, we are unprepared to attempt any such project on another world.

Building a habitat on another world is not a scientific experiment; it's an engineering project.