A lot of stuff is known about it. Both the US and USSR first operated long-duration space stations nearly half a century ago.
Gravity and radiation are well understood and we can definitely build machinery that can tolerate them well for many years.
> we have never entirely isolated a group of humans from the biosphere for even a year, never mind indefinitely. The times it was tried, it failed.
Why doesn't the ISS count? It gets resupplied every few months but a Mars base would be resupplied every two years so systems only have to scale to last 10x as long.
Gravity and radiation are well understood and we can definitely build machinery that can tolerate them well for many years.
> we have never entirely isolated a group of humans from the biosphere for even a year, never mind indefinitely. The times it was tried, it failed.
Why doesn't the ISS count? It gets resupplied every few months but a Mars base would be resupplied every two years so systems only have to scale to last 10x as long.