First I don't think either planet should be terraformed in the near future - it is a process that will take centuries, and most likely millennia. So we can be relaxed about it. If we have a sufficiently stable space economy and society to undertake multi-millennial projects like this, then we will have plenty of time to do it and it is our descendants a few millennia from now who will enjoy the fruits of our
labours.
I don't think that the mere act of starting on such a project will create the long term stability needed to complete it as in Zubrin's optimistic projections. Is far more likely you end with stranded colonists. These I think would soon die, as Mars is so harsh and you can't survive there without sophisticated complex equipment, prone to failure.
Longer term, then I think that Mars is by far the most interesting planet in its pristine state because it probably has intact evidence of the first few hundred million years of evolution towards life, in its ancient seas, and possibly may have present day life also. So for that reason also given the choice would choose Venus.
See How Valuable is Pristine Mars for Humanity
And we don't need to terraform either because there is enough material in the asteroid belt to make Stanford Torus type habitats with cosmic radiation shielding for an area a thousand times the land area of the Earth. Back in the 1970s O'Niel came to the conclusion that the future of space settlement is in free flying space colonies and I think the same is true today, the numbers very much favour space colonies long term.
See Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths
Also the only hard truth we have about terraforming is with Earth where it took billions of years - and for all we know Earth might have been lucky, there might be other directions it could have followed that wouldn't be at all like present day Earth in outcome.
People often talk about "tweaking" the process as it goes along. But that means maintaining interest in the project long term for millennia - when for most of the time the planets are not hospitable for life - and supposes we can do the tweaking at all. Is one thing to tweak a small habitat, is another thing to tweak a planet, look at how hard it is to "tweak" the levels of CO2 on Earth.
Then - it can easily go wrong - especially e.g. if you want to start with a single species or few species, e.g. cyanobacteria, to create oxygen any other microbes that eat or decompose the cyanobacteria or that consume the oxygen will slow down the process hugely - and once introduced, maybe by accident, can't be removed from a planet.
Anyway - there are major issues with both long term. Mars
Venus:
There the idea is that the Earth atmosphere would be a lifting gas on Venus. Just as a hydrogen balloon such as a weather balloon naturally floats high in Earth's atmosphere, so a habitat filled with Earth atmosphere naturally floats high in the Venus atmosphere. Turns out it floats at a level above the cloud tops with the pressure, both inside and outside the habitat - at pretty much Earth normal - and the temperatures in that zone also, coincidentally, are around 0C or just above. Ideal for humans - apart from lack of oxygen and the sulfuric acid droplets. But those seem manageable also - as much so as for Mars
In that sense, I think in some ways Venus is more easily "terraformed" than Mars in the sense that the cloud top levels are almost Earth like already - and no risk of them reverting to a snowball phase or losing its atmosphere.
Not perfect but perhaps if we do ever get colonists living "on" another planet, maybe the Venus cloud colonists would be the first.
So, I think that might happen eventually - probably not right away but maybe a few decades in the future, could be as soon as that. Very much a personal point of view. The idea of Venus cloud colonies has hardly been studied at all in the literature, just the one paper by Geoffrey Landis and the old Russian 1970s proposal and I think we just don't have enough information to know if it is really possible.
Lots of blog posts and discussions about it on the internet now including on the Venus Society at Linkedin.http://www.linkedin.com/groups/V...
There are planetary protection issues for Venus - if there is life in the atmosphere of Venus already - need to be sure that Earth life won't contaminate it or it damage us - at least to start with - could be absolutely unique amazing to study if there is life there. So I think rover missions first.
However, for at least centuries into the future and quite possibly for ever (I am dubious about whether Mars terraforming will ever be possible) - then Earth is by far the best place to terraform in our solar system :).
We might eventually get habitats in space though, free floating - for those self contained colonies I think no great advantage in putting them on a planetary surface. But if we do need to for the first colonies then the lunar poles are the obvious place to do it.
Also in that article, I suggested a fun idea for terraforming both in one go by using a railgun to fire dry ice from Venus atmosphere to Mars. Tthat is obviously sci. fi. at present, if we ever do do it. Is fun to think about it- and also we wouldn't know what the effect would be - that's also in my : Trouble With Terraforming Mars
labours.
I don't think that the mere act of starting on such a project will create the long term stability needed to complete it as in Zubrin's optimistic projections. Is far more likely you end with stranded colonists. These I think would soon die, as Mars is so harsh and you can't survive there without sophisticated complex equipment, prone to failure.
Longer term, then I think that Mars is by far the most interesting planet in its pristine state because it probably has intact evidence of the first few hundred million years of evolution towards life, in its ancient seas, and possibly may have present day life also. So for that reason also given the choice would choose Venus.
See How Valuable is Pristine Mars for Humanity
And we don't need to terraform either because there is enough material in the asteroid belt to make Stanford Torus type habitats with cosmic radiation shielding for an area a thousand times the land area of the Earth. Back in the 1970s O'Niel came to the conclusion that the future of space settlement is in free flying space colonies and I think the same is true today, the numbers very much favour space colonies long term.
See Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths
Also the only hard truth we have about terraforming is with Earth where it took billions of years - and for all we know Earth might have been lucky, there might be other directions it could have followed that wouldn't be at all like present day Earth in outcome.
People often talk about "tweaking" the process as it goes along. But that means maintaining interest in the project long term for millennia - when for most of the time the planets are not hospitable for life - and supposes we can do the tweaking at all. Is one thing to tweak a small habitat, is another thing to tweak a planet, look at how hard it is to "tweak" the levels of CO2 on Earth.
Then - it can easily go wrong - especially e.g. if you want to start with a single species or few species, e.g. cyanobacteria, to create oxygen any other microbes that eat or decompose the cyanobacteria or that consume the oxygen will slow down the process hugely - and once introduced, maybe by accident, can't be removed from a planet.
Anyway - there are major issues with both long term. Mars
- Lower gravity, needs more mass per square meter for same atmospheric pressure
- Huge timescale, you have to keep at it for at most optimistic projection 900 years but most likely tens or hundreds of thousands of years, to complete it - and for the first many centuries is far less hospitable than Earth even immediately after giant impact.
- Further from sun, half the solar radiation, liable to go into "snowball" phases much more easily than the Earth.
- Elliptical orbit. You will get major global storms every 2 years and different climates in the two hemispheres.
- No magnetic field to protect from cosmic radiation, also to prevent atmosphere getting stripped
- No continental drift to recycle CO2 back to atmosphere
- Closer to the asteroid belt with a five times greater risk of one megaton impacts, likely to happen on the surface every three years, instead of every fifteen on Earth
- No stabilizing Moon and axis often tilts so far you get equatorial ice belts
Venus:
- Too much atmosphere - and even if you somehow blast it into space it would just gather it up again gravitationally
- Too hot and too close to the sun
- "Day" is far too long
- No continental drift
- Every few hundred million years the entire surface is resurfaced in a global upheaval
There the idea is that the Earth atmosphere would be a lifting gas on Venus. Just as a hydrogen balloon such as a weather balloon naturally floats high in Earth's atmosphere, so a habitat filled with Earth atmosphere naturally floats high in the Venus atmosphere. Turns out it floats at a level above the cloud tops with the pressure, both inside and outside the habitat - at pretty much Earth normal - and the temperatures in that zone also, coincidentally, are around 0C or just above. Ideal for humans - apart from lack of oxygen and the sulfuric acid droplets. But those seem manageable also - as much so as for Mars
In that sense, I think in some ways Venus is more easily "terraformed" than Mars in the sense that the cloud top levels are almost Earth like already - and no risk of them reverting to a snowball phase or losing its atmosphere.
- many resources we need already in the atmosphere and can be extracted.
- Can grow trees - surprisingly 90% of the mass of a tree consists of the CO2 and water (which can be extracted from the sulfuric acid in the atmosphere) so you may well get colonists growing trees, and wooden habitats created in the Venus atmosphere - doesn't have to be that strong either, no need to hold up to atmospheric pressure.
- Temperature and pressure, by coincidence, are exactly what we need
- The cloud top layer also super-rotates with a "day" of about 4 Earth days which seems something that life might well be able to adjust to
- insulated from the worst effects of the surface volcanoes and millions of years into the future - colonists in cloud cities may be able to survive the resurfacing of the entire crust of Venus also.
- No risk of losing its atmosphere or cooling down, is stable for millions of years.
Not perfect but perhaps if we do ever get colonists living "on" another planet, maybe the Venus cloud colonists would be the first.
So, I think that might happen eventually - probably not right away but maybe a few decades in the future, could be as soon as that. Very much a personal point of view. The idea of Venus cloud colonies has hardly been studied at all in the literature, just the one paper by Geoffrey Landis and the old Russian 1970s proposal and I think we just don't have enough information to know if it is really possible.
Lots of blog posts and discussions about it on the internet now including on the Venus Society at Linkedin.http://www.linkedin.com/groups/V...
There are planetary protection issues for Venus - if there is life in the atmosphere of Venus already - need to be sure that Earth life won't contaminate it or it damage us - at least to start with - could be absolutely unique amazing to study if there is life there. So I think rover missions first.
However, for at least centuries into the future and quite possibly for ever (I am dubious about whether Mars terraforming will ever be possible) - then Earth is by far the best place to terraform in our solar system :).
We might eventually get habitats in space though, free floating - for those self contained colonies I think no great advantage in putting them on a planetary surface. But if we do need to for the first colonies then the lunar poles are the obvious place to do it.
Russian idea for a Venus cloud colony in 1971 - original article (in Russian) - anddiscussion.
I've got an article about all this here: Trouble With Terraforming Mars - which also talks about the Venus ideas as well.Update Answer
Also in that article, I suggested a fun idea for terraforming both in one go by using a railgun to fire dry ice from Venus atmosphere to Mars. Tthat is obviously sci. fi. at present, if we ever do do it. Is fun to think about it- and also we wouldn't know what the effect would be - that's also in my : Trouble With Terraforming Mars
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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