There's an argument that Earth, as a biodome completely isolated from outside with its own atmosphere, also isn't self sustaining. https://en.wikipedia.org/wik

There's an argument that Earth, as a biodome completely isolated from outside with its own atmosphere, also isn't self sustaining. https://en.wikipedia.org/wiki/Earth_Overshoot_Day https://en.wikipedia.org/wiki/Earth_Overshoot_Day I'd keep the Moonraker film in mind as a metric for self sustaining colonies created by billionaires. They can't be trusted unless they are also working to fix what we already have.