How do you experience fresh air in a space station? There will be no fresh air like that in a natural forest on Earth, neither in a Mars station nor in a space station.

I was thinking of a large rotating space station (e.g., a Stanford torus). I would certainly find anything like that preferable to living in a tunnel.

Why are you assuming Mars habitats must consist of a tunnel? If you can build large rotating habitats, you can build surface habitats on Mars that are just as big.

Can we? I would imagine that enclosing large volumes is easier without gravity being a problem.

It's no more of a problem than centrifugal force is for a rotating habitat.

Realistically, neither is a place a sane person would want to live permanently, any more than people would want to live permanently at a research base at the South Pole (and raise kids there). But we've got a small space station, and may have two in a few years (China's "Heavenly Palace"), so there's really no publicity to be gained from building yet another one.

We don't go to space for practical reasons, so when you look for practical reasons for why we do one space mission and not another, you're looking in the wrong place.

Sure gravitation is a concern – but it's not implausible to think that with special exercise, humans can make up for weaker gravity that still works fundamentally the same as on Earth. In the moon missions that wasn't feasible because of space constraints and the moons gravity is so very weak, but for a large scale Mars mission, with modern technology? Should work. – On a space station with artificial gravity (at least a non-absurdly large toroidal one), you may be able to get exactly 1g but that also incurs significant Coriolis forces, which is something humans aren't used to at all.

Once I finish inventing my graviton generator, problems will go away :-)

Er, you'd have to build a facility to contain all the fresh air you're describing. This is a lot easier with gravity and resources. Why would they build a space station? That seems astronomically, impossibly expensive. Mars seems far-fetched, but at least possible.

If you are concerned about gravity you can build a rotating habitat (or at least sleep capsules) on Mars as well. It could even run on tracks.

One thing that hasn't been mentioned is that if something catastrophic were to happen to earth a space station wouldn't help you. Elon specifically wants to prevent extinction

@chrylis -cautiouslyoptimistic: Just the other way around, IMHO. No sane person would have wanted to live in such hellishly hot places when you can live in comfortable Scandinavia :-) But the point is that humans CAN live in either, and can go outside without wearing space suits.

@xyious It's a corollary of the resource argument. An orbital habitat will always be dependent on imported resources, since it has nothing else. Related to this, an orbital habitat will need near-perfect closed life support and recycling from the moment it starts operating, with limited margins for variations in production, consumption, or supply disruptions. Mars has massive reserves of water, CO2, nitrogen, argon, and mineral resources, a colony there doesn't need to be a closed system. (Ceres and several gas giant moons have similar advantages, but are harder to get to.)

the scifi book en.wikipedia.org/wiki/Seveneves demonstrates in a realistic/entertaining way >90% of what is stated in the 3 current top answers. specifically it shows how fragile humanity would be in a space-station environment ... even with relatively few failures. it also shows how a harsh planet can benefit humanity.

I heard that reasoning like what the original question poster uses is actually a key reason why we built the international space station in space, instead of on the moon. Before the first lunar visit, lunar colonies were anticipated. But we found that without atmosphere, the moon is a meteorite-attracting gravity source that doesn't burn up debris in atmosphere, and moving a building on a planet is harder than in space, and so we just built the desired thing in space (and called it the Int'l Space Station). Mars became attractive because of resources like air and ice.

Answers to How might the experience of a trip to Mars differ in comfort and heath impact from a stint on the ISS? address why being in a small-ish spacecraft is feared to be a less pleasant experience than once on Mars, but it's not really the basis for an answer because a space station would likely be much larger and more comfortable than a capsule.

@uhoh: But any realistic Mars vessel would have to be roughly the size of the ISS (and perhaps spun for gravity). Even if your astronauts survived the trip in a capsule, they'd be in no condition to do anything useful on Mars.

This has been a useful discussion. One of the reasons I posted it is that I see space stations as the only way to continue the growth of the human race. I imagine that in 100 years (unless there is a catastrophe), billions will live in enormous space stations. Mars seems to me like a less desirable place to live due to the gravity not being 1 G.

@jamesqf yes that makes sense of course, maybe something like this? imdb.com/title/tt0199753/mediaviewer/rm3318049024 :-)

I'm thinking orders of magnitude bigger.

I believe making a well-going space station on LEO would be far more easy, because we could easily re-supply it with cheap SpaceX flights. But the urge to have a human footstep on the Mars is more important.

@Gene McCulley: But you should be asking why continue the growth of the human race? Seems much more sensible and a LOT cheaper to simply invest in better birth control technologies.

@Gene McCulley Personally, I think that even if low gravity does turn out to prevent proper human development (and this still isn't known for certain; all of our current data is from 0 and 1 g), future humans would figure out a way to adapt to it, whether it's through hormone treatments or genetic engineering or something else. There are advantages to living on a planet, as others have explained on this page.