What would it take to build a self-sustaining astronaut ecosystem on Mars?

> The third stage would begin when the Mars population exceeds 10,000 people. At this point, a Martian colony should have its own bio-foundry to engineer its own microbes on demand. “This won’t happen for a long time, though. It's a possibility only when the planet is colonized. We’re probably hundreds of years away from it,” said Averesh.

Well. There's Clark's first law - "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong." - which isn't directly applicable here, but looks awfully close.

They tried:

https://en.m.wikipedia.org/wiki/Biosphere_2

The assumption appears to be "one" Mars habitat, with a lot of engineered systems to support human (and other) life.

Three would be better, and each should be capable of supporting the population of one of the others (that is, meaningfully under-utilized.)

When, not if, a biosphere breaks down the inhabitants will have a safe refuge.

Meanwhile the under-utilized biosphere can hoard, ummm, accumulate, spare food and water for use in lesser emergencies.