I think we shouldn't have space colonization as our target at all. Either in our solar system or outside of it. Instead, space exploration and space settlement. Both within the solar system and later when exploring the galaxy.
By space settlement I mean, that you are there for some other reason, for instance mining, energy generation, tourism and scientific exploration, and you build settlements similarly to the settlements in Antarctica.
Mostly for short term visitors, for the most part rotating back to Earth after a few years, and may eventually have a few people living there full time - but only because they are financially supported by Earth because they are doing something worthwhile for the Earth, because it's going to be far more expensive to live there full time than live on the Earth.
Because - as you say - Mars is not an ideal Earth analogue, and there is nowhere in our solar system that is anything like as easy to live as Earth and Earth is not totally colonized, many deserts, the entire sea bed / sea surface (whichever you prefer).
Even our atmosphere could be colonized (Buckminster Fuller's ideas for spherical cities that float in the atmosphere, lifted up by their own internal heat - if the city is large enough then it is technically possible to do this, easily strong enough in spherical shape also)
These are all far far easier to colonize than outer space. You could build a city floating in the atmosphere probably more easily than a city on the Moon or Mars or a Stanford Torus. Construction is far easier for one. There is no need for spacesuits, you have materials to hand, easily transported to the building site, no need for transport from Earth. No need for a closed ecosystem when done, as the atmosphere is breathable anyway. No need to spin for gravity, again reduces requirements for construction. Far lighter construction, doesn't have to contain air at ten tons per square meter as the atmospheric pressure is the same inside and out.
Venus is about the only planet where you can do lightweight construction which is nearly as easy as Earth, in the upper atmosphere at the top of the cloud layer, floating cloud colonies, but of course it has other issues, including non breathable atmosphere and sulfuric acid.
As for colonizing the rest of the galaxy, what's the hurry? We don't need to be a "two planet species" to avoid disasters, because there is no credible disaster that would make humans throughout the Earth extinct. Even an impact with a giant asteroid - there would be human survivors, if nothing else, in submarines. Tsunami and firestorms are surface events, and would have no effect at all on the deep ocean, a submarine wouldn't even notice it, and would surface after it is all over, and its crew could then repopulate the Earth. And for that matter even in the worst examples of an impact in the geological record over the last few billion years, you'd be able to survive the impact itself on the surface, so long as you had protection from a firestorm. And then can rebuild afterwards - need stores to last you through a few years before the climate is restored and crops are possible.
So would be easy to set up "backups" on the Earth to see us through disasters like that.
However, if you have settlements in space anyway, financially supported from the Earth because they are valuable in other ways, then it's reasonable to use them as an additional backup. The more the better :). If you had that in mind - then they need to have the capability to move their population back to Earth under their own initiative. Because, surely, they would want to come back to Earth as the first thing they do after a disaster, as Earth would remain the most habitable planet in our solar system. It would make sense anyway for a space settlement to have "lifeboat" spaceships to hand sufficient to move their entire population back to Earth, similarly to the ISS which is required to have spacecraft with capacity to move entire crew back to Earth docked to the station at all times. With future technology and reusable spacecraft, those could be spacecraft capable of shuttling back and forth between the settlement and Earth.
Here the thing is, that you have the light speed delay issue. If we colonize the galaxy, no way can you have an overview of the entire galaxy.
Some issue could develop, say ten thousand light years from here, and if the problem spreads through the galaxy at just a tenth of the speed of light (easily possible with future technology) then it covers a patch of the galaxy a thousand light years in radius before we know about it.
For instance - someone lets loose a self replicator that turns everything into paper clips or a mini black hole machine that makes micro black holes and fires them at suns to turn them into black holes. Maybe for fun, descendents of us that are immensely powerful but lost capability for crictical thought and are like children in their intellect - or maybe just by mistake and stupidity.
Or could be cyborgs, or biological entities. E.g. a fan of Aliens thinks it would be cool to create a biological entity that is as close as possible a replica of the monster in that movie and set it loose on the galaxy. Or beings that are created with good intentions that then evolve by themselves.
Again - these beings - replicators whether biological or mechanical - they could have colonized a sphere a thousand light years in radius before we know that the problem exists.
For that matter, they might develop faster than light technology, or might find ways of seeding self replicators by firing them at the speed of light or close to it. Might spread through the galaxy at close to the speed of light, totally undetectable until they get to you. And when they get here, stop by aerobraking in the sun and atmospheres of planets and giant planets - but do so as tiny particles so small you need an electron microscope to spot them.
Or you have several Jupiter's worth of these things by mass converging from nearby solar systems.
And technology bound to be uneven. Eventually some star systems would be thousands of years ahead in some technological areas, or just about all technological areas compared with others.
This is not science fiction, any more than colonizing the galaxy is. If we colonize the galaxy, then eventually, this will happen, that we get technology that is thousands of years, millions of years ahead of what we have now, spread throughout the galaxy, and uneven development of it.
I am not at all sure that this is a good future to aim for.
May be ways around it. May be that we discover Faster Than Light (FTL) travel, so entire galaxy can be treated as a single unit like the Earth, same technological development and understanding of physics throughout. Maybe development of our understanding, so that we can be confident that no future humans or our creations could do anything that is problemantical for the galaxy.
Or might be that humans see this possibility and decide not to colonize. There is no evolutionary imperative to colonize, because we are thinking beings.
Might be indeed that evolution counts against colonization. That creatures that would be prone to colonize are so reckless and unthinking about their future that they also destroy their space settlements long before they get the chance. So that the only ones left are the ones who are forward thinking enough to consider the implications and decide to explore the galaxy rather than colonize it.
So then - you'd have research settlements maybe eventually throughout the galaxy. Occasional intergalactic tourists perhaps and adventurers. But nobody would even think about setting up a colony without great care - that would be thought of similarly to setting off a nuclear weapon, but far worse.
That might be one of the reasons why ETIs haven't colonized the Earth yet.
I think is reasonably clear that no ETI has colonized the galaxy at least not in the way that humans would, because we don't see any signs of any of this sort of thing going on - and if they did - they would be here already. Our solar system would have been colonized millions of years ago. We would see, at the very least, the ruins of their cities on the Earth and their derelict space stations filling the solar system - it would be obvious to anyone that they had been here, if they were at all like humans would be if they colonized the galaxy in their present form. Because there would be nothing to stop us. Even spreading at a tiny fraction of the speed of light, even with many civilizations destroying themselves in the process - at some point then the entire galaxy gets colonized, in just a "blink of time" relative to the age of the galaxy.
So if technological ETIs ever embarked on this in the past, they should be here, and they aren't, and chances that they arise in the same geological moment as us is too remote to be credible.
So, I think myself that probably we will decide not to colonize the galaxy. Or if we do, will be in some way that is so unintrusive that you hardly notice our presence.
If we are first in our galaxy then we have to be especially careful here.
And our galaxy may have numerous non technological ETIs also, that may be advanced in other areas but just don't have hands, or live in the sea, maybe covered in ice like Europa. They would be totally vulnerable to a colonizing wave of humans, some at least wouldn't respect them at all or be interested in their billions of years old civilizations.
We need to consider that possibility also. And not unleash humans on the galaxy - we have so many science fiction stories about ET monsters invading Earth. We need to make sure humans don't become the ET monsters of those stories, either for other ETIs in our galaxy - or indeed for ourselves, as our descendants or their creations converge back on Earth after thousands, eventually millions of years in the rest of the galaxy.
Exploration and temporary space settlement has none of these issues. And lets us find out about the solar system and galaxy. Knowing more about this will surely help us to make the right decision.
Not saying that we shouldn't ever colonize. But let's explore first, and learn about the solar system and galaxy first. And then decide.
SPACE SETTLEMENT
By space settlement I mean, that you are there for some other reason, for instance mining, energy generation, tourism and scientific exploration, and you build settlements similarly to the settlements in Antarctica.
Mostly for short term visitors, for the most part rotating back to Earth after a few years, and may eventually have a few people living there full time - but only because they are financially supported by Earth because they are doing something worthwhile for the Earth, because it's going to be far more expensive to live there full time than live on the Earth.
WHY FOCUS ON SPACE SETTLEMENT AND EXPLORATION FOR THE SOLAR SYSTEM
Because - as you say - Mars is not an ideal Earth analogue, and there is nowhere in our solar system that is anything like as easy to live as Earth and Earth is not totally colonized, many deserts, the entire sea bed / sea surface (whichever you prefer).
Even our atmosphere could be colonized (Buckminster Fuller's ideas for spherical cities that float in the atmosphere, lifted up by their own internal heat - if the city is large enough then it is technically possible to do this, easily strong enough in spherical shape also)
These are all far far easier to colonize than outer space. You could build a city floating in the atmosphere probably more easily than a city on the Moon or Mars or a Stanford Torus. Construction is far easier for one. There is no need for spacesuits, you have materials to hand, easily transported to the building site, no need for transport from Earth. No need for a closed ecosystem when done, as the atmosphere is breathable anyway. No need to spin for gravity, again reduces requirements for construction. Far lighter construction, doesn't have to contain air at ten tons per square meter as the atmospheric pressure is the same inside and out.
Venus is about the only planet where you can do lightweight construction which is nearly as easy as Earth, in the upper atmosphere at the top of the cloud layer, floating cloud colonies, but of course it has other issues, including non breathable atmosphere and sulfuric acid.
As for colonizing the rest of the galaxy, what's the hurry? We don't need to be a "two planet species" to avoid disasters, because there is no credible disaster that would make humans throughout the Earth extinct. Even an impact with a giant asteroid - there would be human survivors, if nothing else, in submarines. Tsunami and firestorms are surface events, and would have no effect at all on the deep ocean, a submarine wouldn't even notice it, and would surface after it is all over, and its crew could then repopulate the Earth. And for that matter even in the worst examples of an impact in the geological record over the last few billion years, you'd be able to survive the impact itself on the surface, so long as you had protection from a firestorm. And then can rebuild afterwards - need stores to last you through a few years before the climate is restored and crops are possible.
So would be easy to set up "backups" on the Earth to see us through disasters like that.
However, if you have settlements in space anyway, financially supported from the Earth because they are valuable in other ways, then it's reasonable to use them as an additional backup. The more the better :). If you had that in mind - then they need to have the capability to move their population back to Earth under their own initiative. Because, surely, they would want to come back to Earth as the first thing they do after a disaster, as Earth would remain the most habitable planet in our solar system. It would make sense anyway for a space settlement to have "lifeboat" spaceships to hand sufficient to move their entire population back to Earth, similarly to the ISS which is required to have spacecraft with capacity to move entire crew back to Earth docked to the station at all times. With future technology and reusable spacecraft, those could be spacecraft capable of shuttling back and forth between the settlement and Earth.
WHY FOCUS ON SPACE EXPLORATION AND SETTLEMENT WHEN EXPLORING THE GALAXY
Here the thing is, that you have the light speed delay issue. If we colonize the galaxy, no way can you have an overview of the entire galaxy.
Some issue could develop, say ten thousand light years from here, and if the problem spreads through the galaxy at just a tenth of the speed of light (easily possible with future technology) then it covers a patch of the galaxy a thousand light years in radius before we know about it.
For instance - someone lets loose a self replicator that turns everything into paper clips or a mini black hole machine that makes micro black holes and fires them at suns to turn them into black holes. Maybe for fun, descendents of us that are immensely powerful but lost capability for crictical thought and are like children in their intellect - or maybe just by mistake and stupidity.
Or could be cyborgs, or biological entities. E.g. a fan of Aliens thinks it would be cool to create a biological entity that is as close as possible a replica of the monster in that movie and set it loose on the galaxy. Or beings that are created with good intentions that then evolve by themselves.
Again - these beings - replicators whether biological or mechanical - they could have colonized a sphere a thousand light years in radius before we know that the problem exists.
For that matter, they might develop faster than light technology, or might find ways of seeding self replicators by firing them at the speed of light or close to it. Might spread through the galaxy at close to the speed of light, totally undetectable until they get to you. And when they get here, stop by aerobraking in the sun and atmospheres of planets and giant planets - but do so as tiny particles so small you need an electron microscope to spot them.
Or you have several Jupiter's worth of these things by mass converging from nearby solar systems.
And technology bound to be uneven. Eventually some star systems would be thousands of years ahead in some technological areas, or just about all technological areas compared with others.
This is not science fiction, any more than colonizing the galaxy is. If we colonize the galaxy, then eventually, this will happen, that we get technology that is thousands of years, millions of years ahead of what we have now, spread throughout the galaxy, and uneven development of it.
I am not at all sure that this is a good future to aim for.
May be ways around it. May be that we discover Faster Than Light (FTL) travel, so entire galaxy can be treated as a single unit like the Earth, same technological development and understanding of physics throughout. Maybe development of our understanding, so that we can be confident that no future humans or our creations could do anything that is problemantical for the galaxy.
Or might be that humans see this possibility and decide not to colonize. There is no evolutionary imperative to colonize, because we are thinking beings.
Might be indeed that evolution counts against colonization. That creatures that would be prone to colonize are so reckless and unthinking about their future that they also destroy their space settlements long before they get the chance. So that the only ones left are the ones who are forward thinking enough to consider the implications and decide to explore the galaxy rather than colonize it.
So then - you'd have research settlements maybe eventually throughout the galaxy. Occasional intergalactic tourists perhaps and adventurers. But nobody would even think about setting up a colony without great care - that would be thought of similarly to setting off a nuclear weapon, but far worse.
That might be one of the reasons why ETIs haven't colonized the Earth yet.
I think is reasonably clear that no ETI has colonized the galaxy at least not in the way that humans would, because we don't see any signs of any of this sort of thing going on - and if they did - they would be here already. Our solar system would have been colonized millions of years ago. We would see, at the very least, the ruins of their cities on the Earth and their derelict space stations filling the solar system - it would be obvious to anyone that they had been here, if they were at all like humans would be if they colonized the galaxy in their present form. Because there would be nothing to stop us. Even spreading at a tiny fraction of the speed of light, even with many civilizations destroying themselves in the process - at some point then the entire galaxy gets colonized, in just a "blink of time" relative to the age of the galaxy.
So if technological ETIs ever embarked on this in the past, they should be here, and they aren't, and chances that they arise in the same geological moment as us is too remote to be credible.
So, I think myself that probably we will decide not to colonize the galaxy. Or if we do, will be in some way that is so unintrusive that you hardly notice our presence.
If we are first in our galaxy then we have to be especially careful here.
And our galaxy may have numerous non technological ETIs also, that may be advanced in other areas but just don't have hands, or live in the sea, maybe covered in ice like Europa. They would be totally vulnerable to a colonizing wave of humans, some at least wouldn't respect them at all or be interested in their billions of years old civilizations.
We need to consider that possibility also. And not unleash humans on the galaxy - we have so many science fiction stories about ET monsters invading Earth. We need to make sure humans don't become the ET monsters of those stories, either for other ETIs in our galaxy - or indeed for ourselves, as our descendants or their creations converge back on Earth after thousands, eventually millions of years in the rest of the galaxy.
Exploration and temporary space settlement has none of these issues. And lets us find out about the solar system and galaxy. Knowing more about this will surely help us to make the right decision.
Not saying that we shouldn't ever colonize. But let's explore first, and learn about the solar system and galaxy first. And then decide.
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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