First of all - those disasters are amazingly unlikely in near future, you are talking about chances in a million. But supposing the worst case.
Look around our solar system, no other planet is even close to Earth in it's hospitality for life. To make Earth as hostile to life as Mars you have to
It's pretty obvious that no matter what we do, we aren't going to make Earth as hostile a place to live as Mars. And nor is any natural disaster, not in the next few million years at least. None of those disasters come close to it.
For example worst possible asteroid impact, judging by impact crater records on Moon, etc - would be one perhaps 100 km across or so, that causes a global firestorm and an impact winter for several years afterwords (the lunar Mare and largest craters on the Moon were created in the first few hundred million years of the solar system before it settled down into its present state - the more recent craters are smaller). And chance of that tiny, 0.0001% or less of it happening before 2100. And this is one of the most likely of all the scenarios.
Nowhere near making Earth inhospitable to Earth life, and many humans also could survive. If that's what made the dinosaurs extinct - it's because they had no technology to protect them.
A few hundred million years from now, a billion years from now, yes, Earth will become uninhabitable (unless we find a way to prevent that e.g. through mega-engineering.
But that's long enough timescale for humans to evolve for a second time from the very first multi-cellular creatures, so I think it's a bit early to worry about that quite yet.
What about Venus?
Well the surface of Venus is so hostile, nobody can even spend as much as a few minutes there, you'd be simultaneously crushed, melted and suffocated.
The upper atmosphere of Venus is more Earth like, and - the closest to Earth conditions you can find in our solar system.
See Robert Walker's answer to Why are we thinking about a Mars colony when a Venus colony would be more technically feasible? It seems that radiation shielded floating colonies could be assembled on Venus, with plastic film and aluminum wire bags, filled with breathable air.
Still - no matter what you do to Earth, again to get it as hostile as the upper atmosphere of Venus you have to
With Venus upper atmosphere, - well this is an opinion - in my view, it's a major plus, that
That's something you have already with the Venus upper atmosphere - which the visonaries with ideas for terraforming Mars only hope to achieve after 1000 years of terraforming.
Still - nothing we do to Earth is likely to make it anything like as uninhabitable even as the upper Venus atmosphere.
Even oxygen, some people worry that by cutting down the forests we will lose the oxygen in the atmosphere.
But - no - that's not going to happen. The residence time is 4500 years for oxygen in the Earth atmosphere. That means, that even if we got rid of nearly all plant life on Earth - it would take several millennia before it lost its oxygen to the level where humans can't breath here any more.
Long before then, plants would recolonize the land. There are larger yearly fluctuations - but if you got rid of all plant life, then those fluctuations would stop, you wouldn't just lose all the oxygen as there would be no plants left to take it up from the atmosphere.
We have enough fossil fuel to warm the Earth up by several degrees and melt Antarctica. But even if we burnt all the fossil fuel reservoirs (including coal and oil shale) without doing any carbon capture - still we don't have enough to cause a runaway greenhouse effect in the atmosphere.
Earth would remain pretty much the same as today.
It is devastating for many humans as parts of the Earth get far hotter, or drier, or in some cases wetter, possibly in some cases even colder, many storms. Also, sea levels rise so that coastal cities and islands and low lying nations become flooded. Many species become extinct because they can't move fast enough to find suitable habitats.
There are plenty enough problems to cause misery to billions of humans - that's why we want to prevent global warming.
But overall, it's not going to make Earth significantly less habitable in the long term. Nowhere near making it less habitable than the Venus upper atmosphere or Mars.
Some worry about asteroid impacts. But those - they are climate changing, the largest ones, but only on the short term. The one that brought the end to the dinosaurs may have caused a global firestorm. It may have caused "impact winters" for several years afterwards, enough to make the dinosaurs extinct (without our technology).
It couldn't make humans extinct - even in worst case probably some areas hardly affected by the firestorm because there is nothing to burn (e.g. the polar regions perhaps) and some humans would survive underground or in the sea, even with no preparation at all (e.g. in submarines, or deep in mines in regions without firestorms).
Also in practice would expect at least months of preparation, much of the worlds population might well survive - and - chance of this happening before 2100 is less than 0.0001%!
I don't think many realize quite how tiny these chances are.
That chance of a big civilization threatening impact is likely to go down to less than 0.00001% by the 2020s (unless of course we discover one by then if so then with lots of warning can start on plans to divert it).
What is the probability of a significant asteroid impact event by 2100?
And afterwards, Earth would still remain, by far, the very best place in the solar system to restore - it would still have
As for planets around other suns, well we are probably centuries away from any technology that would make it practical to move a significant part of our population through interstellar distances. If that is ever necessary at all.
We could build colonies in space. That's perhaps more practical than migrating to another planet - it depends how it scales up. For a colony with small habitats like the ISS - then that's obviously - probably always - going to be much harder to do than building on the Earth.
But a big Stanford Torus type colony - if easy to maintain - might be easier to do than any other form of space colonization. Idea here is - you build the habitat - that's expensive - but then build houses inside - and as long as the habitat is reasonably easy to maintain - with the cost spread over its 10,000 or more residents - then it might not be that much more expensive than living on the Earth. That depends on how easy it is to maintain a Stanford Torus in practise.
Still - hard to see those being as easy to build as floating "Cloud Nine" type cities in the Earth's atmosphere, or "Sea Cities" floating on the ocean - or Seawater Greenhouses in the deserts, all of which could be made pretty much immune to whatever we do to the Earth.
So - I think for foreseeable future, even taking account of space colonies, then no matter what we do to the Earth, combining worst effects of all the things that could go wrong in the next century or so - we simply can't make it so inhospitable that anywhere else in the solar system is a better place for humans than Earth.
Hopefully this helps us to focus our attention on the Earth itself, where we can make a huge difference with our actions.
And space exploration and also perhaps settlement may help us in many ways, for sure. But not, I think, by helping us to escape from Earth, looking for a brighter future elsewhere. I see no future in that myself. Our brightest future is on Earth itself!
For now and for the foreseeable future. Sometimes the space enthusiasts talk about how 3D printers would change everything. Sure, perhaps they might - but on Earth also.
If we get to the point where we can make a spaceship or spacesuit from a 3D printer, we can use 3D printers on the Earth to do miracles also, and still, I think, Earth will have the edge by far over space - because of its breathable atmosphere, climate, radiation protection, liquid water, natural ecosystems already here, etc etc.
Look around our solar system, no other planet is even close to Earth in it's hospitality for life. To make Earth as hostile to life as Mars you have to
- Remove 99% of its atmosphere
- Remove more than 99% of the oxygen that remains after you did that
- Remove all the oceans
- Remove all the ice except a few meters in Antarctica
- Remove its magnetic field (which helps protect from solar storms
- Reduce its gravity to 40%
- Move it further away from the sun - or use orbiting sun shades to cool it down - so that the equator, e.g. Sahara desert, gets about the same level of heat and light from the sun as we currently get in Canada.
It's actually worse than that suggests - because - without the warming effect of our atmosphere - it would actually get as cold as Antarctica (Earth would become ice covered if it had any water left)Sahara by Luca Galuzzi 2007
as cold as
It's pretty obvious that no matter what we do, we aren't going to make Earth as hostile a place to live as Mars. And nor is any natural disaster, not in the next few million years at least. None of those disasters come close to it.
For example worst possible asteroid impact, judging by impact crater records on Moon, etc - would be one perhaps 100 km across or so, that causes a global firestorm and an impact winter for several years afterwords (the lunar Mare and largest craters on the Moon were created in the first few hundred million years of the solar system before it settled down into its present state - the more recent craters are smaller). And chance of that tiny, 0.0001% or less of it happening before 2100. And this is one of the most likely of all the scenarios.
Nowhere near making Earth inhospitable to Earth life, and many humans also could survive. If that's what made the dinosaurs extinct - it's because they had no technology to protect them.
A few hundred million years from now, a billion years from now, yes, Earth will become uninhabitable (unless we find a way to prevent that e.g. through mega-engineering.
But that's long enough timescale for humans to evolve for a second time from the very first multi-cellular creatures, so I think it's a bit early to worry about that quite yet.
What about Venus?
Well the surface of Venus is so hostile, nobody can even spend as much as a few minutes there, you'd be simultaneously crushed, melted and suffocated.
The upper atmosphere of Venus is more Earth like, and - the closest to Earth conditions you can find in our solar system.
See Robert Walker's answer to Why are we thinking about a Mars colony when a Venus colony would be more technically feasible? It seems that radiation shielded floating colonies could be assembled on Venus, with plastic film and aluminum wire bags, filled with breathable air.
Still - no matter what you do to Earth, again to get it as hostile as the upper atmosphere of Venus you have to
- Get rid of all the oxygen
- Arrange (by moving closer to sun or mirrors) that Earth gets so much sunlight that Canada gets as as much sunlight as the Mediterranean, and the Med, more than the Sahara desert.
- Remove all the water in all the seas, and this time, all the ice also, except a bit of moisture in the atmosphere
- What water left in the atmosphere consists of droplets of concentrated sulfuric acid
- Ground so hot (e.g. make it molten lava) or in some other way so inhospitable that you can only survive by floating in the atmosphere in floating habitats.
With Venus upper atmosphere, - well this is an opinion - in my view, it's a major plus, that
- you have the ability to build lightweight habitats
- able to go outside of your habitat with just an air breather and protection suits (to protect from the sulfuric acid)
That's something you have already with the Venus upper atmosphere - which the visonaries with ideas for terraforming Mars only hope to achieve after 1000 years of terraforming.
Still - nothing we do to Earth is likely to make it anything like as uninhabitable even as the upper Venus atmosphere.
Even oxygen, some people worry that by cutting down the forests we will lose the oxygen in the atmosphere.
But - no - that's not going to happen. The residence time is 4500 years for oxygen in the Earth atmosphere. That means, that even if we got rid of nearly all plant life on Earth - it would take several millennia before it lost its oxygen to the level where humans can't breath here any more.
Long before then, plants would recolonize the land. There are larger yearly fluctuations - but if you got rid of all plant life, then those fluctuations would stop, you wouldn't just lose all the oxygen as there would be no plants left to take it up from the atmosphere.
We have enough fossil fuel to warm the Earth up by several degrees and melt Antarctica. But even if we burnt all the fossil fuel reservoirs (including coal and oil shale) without doing any carbon capture - still we don't have enough to cause a runaway greenhouse effect in the atmosphere.
Earth would remain pretty much the same as today.
It is devastating for many humans as parts of the Earth get far hotter, or drier, or in some cases wetter, possibly in some cases even colder, many storms. Also, sea levels rise so that coastal cities and islands and low lying nations become flooded. Many species become extinct because they can't move fast enough to find suitable habitats.
There are plenty enough problems to cause misery to billions of humans - that's why we want to prevent global warming.
But overall, it's not going to make Earth significantly less habitable in the long term. Nowhere near making it less habitable than the Venus upper atmosphere or Mars.
Some worry about asteroid impacts. But those - they are climate changing, the largest ones, but only on the short term. The one that brought the end to the dinosaurs may have caused a global firestorm. It may have caused "impact winters" for several years afterwards, enough to make the dinosaurs extinct (without our technology).
It couldn't make humans extinct - even in worst case probably some areas hardly affected by the firestorm because there is nothing to burn (e.g. the polar regions perhaps) and some humans would survive underground or in the sea, even with no preparation at all (e.g. in submarines, or deep in mines in regions without firestorms).
Also in practice would expect at least months of preparation, much of the worlds population might well survive - and - chance of this happening before 2100 is less than 0.0001%!
I don't think many realize quite how tiny these chances are.
That chance of a big civilization threatening impact is likely to go down to less than 0.00001% by the 2020s (unless of course we discover one by then if so then with lots of warning can start on plans to divert it).
What is the probability of a significant asteroid impact event by 2100?
And afterwards, Earth would still remain, by far, the very best place in the solar system to restore - it would still have
- oxygen,
- water,
- temperatures right
- able to breath the atmosphere and walk on the surface without spacesuits
- grow plants right away
- Protected from UV light and cosmic radiation and solar storms - you won't get cancer from walking around in the open air. Even after a nuclear war - worst case - then even right away, Earth would be far more hospitable than Mars with its constant cosmic radiation and solar flares so long as you avoid the hot spots and filter the air, and after a few decades back pretty much to normal over much of its surface.
- build buildings by ordinary methods without the need to contain tons of atmosphere per square meter
As for planets around other suns, well we are probably centuries away from any technology that would make it practical to move a significant part of our population through interstellar distances. If that is ever necessary at all.
We could build colonies in space. That's perhaps more practical than migrating to another planet - it depends how it scales up. For a colony with small habitats like the ISS - then that's obviously - probably always - going to be much harder to do than building on the Earth.
But a big Stanford Torus type colony - if easy to maintain - might be easier to do than any other form of space colonization. Idea here is - you build the habitat - that's expensive - but then build houses inside - and as long as the habitat is reasonably easy to maintain - with the cost spread over its 10,000 or more residents - then it might not be that much more expensive than living on the Earth. That depends on how easy it is to maintain a Stanford Torus in practise.
Still - hard to see those being as easy to build as floating "Cloud Nine" type cities in the Earth's atmosphere, or "Sea Cities" floating on the ocean - or Seawater Greenhouses in the deserts, all of which could be made pretty much immune to whatever we do to the Earth.
So - I think for foreseeable future, even taking account of space colonies, then no matter what we do to the Earth, combining worst effects of all the things that could go wrong in the next century or so - we simply can't make it so inhospitable that anywhere else in the solar system is a better place for humans than Earth.
Hopefully this helps us to focus our attention on the Earth itself, where we can make a huge difference with our actions.
And space exploration and also perhaps settlement may help us in many ways, for sure. But not, I think, by helping us to escape from Earth, looking for a brighter future elsewhere. I see no future in that myself. Our brightest future is on Earth itself!
For now and for the foreseeable future. Sometimes the space enthusiasts talk about how 3D printers would change everything. Sure, perhaps they might - but on Earth also.
If we get to the point where we can make a spaceship or spacesuit from a 3D printer, we can use 3D printers on the Earth to do miracles also, and still, I think, Earth will have the edge by far over space - because of its breathable atmosphere, climate, radiation protection, liquid water, natural ecosystems already here, etc etc.
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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