I think the radiation exposure might be manageable though, as at least in theory you can shield the habitats.
The showstopper could be the low gravity - we haven’t really done many experiments on low gravity, the Mars Gravity Biosatellite never got built. But if it turns out that Martian gravity is really damaging to human health and thus long-term habitation is not viable then I think we’d have to really rethink our human spaceflight goals as on a planet you don’t even have the option to simulate gravity via the centrifugal force - so it could just be game over for Mars colonisation.
I think the radiation exposure might be manageable though, as at least in theory you can shield the habitats.
The showstopper could be the low gravity - we haven’t really done many experiments on low gravity, the Mars Gravity Biosatellite never got built. But if it turns out that Martian gravity is really damaging to human health and thus long-term habitation is not viable then I think we’d have to really rethink our human spaceflight goals as on a planet you don’t even have the option to simulate gravity via the centrifugal force - so it could just be game over for Mars colonisation.