Originally Answered: Can human life be sustainable on Mars?
It is CO2 which is poisonous to humans at levels of 1% or more, so in order to have a breathable atmosphere you need both oxygen and nitrogen.
Mars probably hasn't got enough CO2 left (in the form of dry ice) to make an Earth pressure atmosphere. We know of enough to raise the pressure to 2% of Earth's but that is not enough. Bad News for Terraforming: Mars' Atmosphere Is Lost in Space
Also think how much industry was needed, how many tons of coal needed to be burnt to raise the amount of CO2 by a fraction of a percent? And how hard it is to do anything to remove this excess CO2 from the atmosphere now it is there - just 0.01% yet we can't remove it, not easily.
It's taken three decades of world wide cars and fossil fuel burning to raise the Earth's CO2 levels from 0.03% to 0.04%. It's not easy to make significant changes in the atmosphere of an entire planet.
Changing the atmosphere of an entire planet is a lot of work. The more optimistic ideas for Mars terraforming suggest a thousand years to get to the point where trees could grow, not yet humans breath the air, humans using air breathers - but that's assuming there is enough CO2 there in the first place.
It is far too cold for trees though. Even if you could give Mars an atmosphere as thick as Earth's by impacting comets say, lots of them - it would still be too cold.
So in those plans, they also add lots of greenhouse gases as well to keep it warm - and do so continuously into the future, because the "blanket" of Earth's atmosphere is not warm enough for Mars (it gets about half the amount of sunlight that Earth gets). By lots, they mean, mining of the order of a cubic kilometer of fluoride ore every decade in order to make greenhouse gases to keep Mars warm, and you keep that up into the indefinite future.
Or you have thin film mirrors in space with the total area of the mirrors equal to the cross section of Mars, of order tens of millions of square kilometers of space mirrors, to reflect sunlight to double the amount it receives. Those again have to be maintained and kept positioned accurately into the indefinite future.
And there is lots to go wrong. We have never yet built even a 10 kilometers square living area space station with a closed habitat system. We haven't even built a three person space station able to grow its own food and make all its own oxygen from plants. We are a long way away from the level of knowledge needed for terraforming any planet. And if we bash in and "give it ago", it is an irreversible process as soon you start introducing new life forms to the planet. What if we choose the wrong lifeforms to introduce, through ignorance? Or through a miscalculation? Or not taking account of some factor in our models?
It looks habitable in the photographs but that's because
- The photos are white balanced to make it look Earth-like. This is not to deceive - it's done that way so that scientists can identify the rocks more easily because then they look the same colour as Earth rocks. But on Mars the sun is dimmer, but as well, there's a fine dust in the atmosphere all the time which takes nearly all the blue light out of the sunlight making everything a kind of yellowish brown in colour, no matter its real colour.
- It looks much warmer than it is, because it has lost nearly all its water. If it hadn't lost it's water, the entire planet would be covered in ice right to the equator.
- You can't tell just from the photos that it has almost no atmosphere, and that what there is is unbreathable CO2.
- There is no native life to eat as far as we know.
- All the oxygen and nitrogen in the air you breath has to be made. Recycled around through plants in greenhouses or made using machines. Never before have pioneers had to generate all their own oxygen in situ, just in order to breath, (sometimes they bring it with them, e.g. for Mount Everest or aqualunging but that's not practical for Mars)..
Trying to colonize Mars right now is as if Shackleton was to try to colonize Antarctica on the first Shackleton expedition.
Endurance - Shackleton's ship just before it sank on his ill fated expedition to Antarctica which however ended with everyone surviving due to heroic and brave leadership. Shackleton didn't attempt to colonize Antarctica, which is far more habitable than Mars.
There was no Antarctic treaty back then to stop him or anyone else. Any of the early polar adventurers could have attempted to set up a colony in Antarctica, just nobody saw any point and it would have been hugely expensive and impractical.
Antarctica is far more habitable than Mars but there is no great wish to colonize it even with modern technology which makes it far easier than in Shackleton's day.
Similarly we could colonize the sea surface, or the upper atmosphere (Buckminster's "cloud nine" idea to use his geodesic spheres as kilometer scale floating cities). Or we could colonize the Gobi desert or the Sahara desert or the Arizona desert. Or glaciers, or high mountains. All of these far far easier to colonize than Mars. There are many places we could, in principle, colonize with our modern technology at great expense, but don't. Because it is just not worth it.
Mars is like that. But it is of great interest to explore. And the best way to explore it is from orbit I think from either Phobos or Deimos or an elliptical orbit, using robotic avatars on the surface. Or continue to explore it from Earth with increasingly capable robotic explorers.
Because the one thing we must not do is to introduce Earth life to Mars while we try to search it to find out if it ever had life and if it does have life now. It would be a scientific tragedy if the end result of all these expeditions to look for life on Mars was that we find a lifeform we brought to the planet ourselves.
It also turns out, in the only comparison study I know, it's much more effective to explore from orbit in terms of the amount of science you can do with the same number of people. And far safer.
The ideas they developed for terraforming Mars or for colonizing it are very interesting. There are lots of innovative things there to think about. But I don't think they are the least bit practical for actually colonizing Mars, myself. And at any rate it would be irreversible, as soon as you introduce Earth life to Mars - you'd better be sure that's what you want to do. Not just you, but everyone on Earth is impacted by an irreversible transformation of Mars. It's not something that should be left to a group of enthusiasts.
Though building space stations - that is not impacting on a whole planet, that is not irreversible, even building large space stations like the Stanford Torus idea of a space habitat large enough to house 10,000 people, and settlements, say domed cities or in caverns on the Moon, or Mars' moons, or in free orbit around the sun, done responsibly, doesn't impact on anyone else's researches and future prospects.
See also my
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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