Originally Answered: Could we terraform the planet Mars?
First - the Earth itself took hundreds of millions of years to "terraform" - a process we don't understand that well.
Then, after that it went into a snowball phase several times when it was almost lifeless again - and only recovered, not through action of life - but because of continental drift and volcanoes bringing CO2 to the surface.
So I think a lot of people have this naive idea - that we just need to seed Mars with life, give it a bit of encouragement, and within a few centuries, almost by itself, with a bit of guidance, it will turn into Earth, with maybe a few mirrors in space and greenhouse factories to help it along.
But even a duplicate Earth, same in all respects except without life, probably couldn't be terraformed as easily as that. And Mars is tremendously different from Earth.
- Further from the sun - move the Earth out to Mars orbit and its oceans would freeze over turning it into "Snowball Earth"
- No magnetic field. Mars has only a few magnetic field hot spots but no protection from the solar wind.
- Lack of water - perhaps due to lack of magnetic field. Mars has lost nearly all its water. It's believed, that it started with less water than Earth originally - but it doesn't seem to have as much water left now as it did when it had global oceans. What has happened to it remains a mystery.
It does have ice at both poles, but in the equatorial regions is believed to be dry for kms below the surface as all the ice would be slowly lost by repeated sublimation towards the surface.
It does have enough water, theoretically, to cover the surface to a depth of some meters - certainly enough for local flooding in high lattitudes - but if it was warmed up globally - wouldn't it all just sink into the dry equatorial regions?
In any case, if we add water to it again - will lose it eventually - not known how exactly but part of the reason may be dissociation of hydrogen from H20, which then escapes to space - in upper atmosphere - because of its lack of a magnetic field to protect it. - No continental drift - long term this returns CO2 to our atmosphere and is what got Earth out of its occasional snowball phase in the past. So if Mars turns into a snowball (which it is basically already but without the ice) - it can't get out of it again
- 40% of Earth's gravity - this means - that for the same atmospheric pressure you need nearly three times as much mass of the gas per square meter
- Orbit elongated a lot more than the Earth's
- No Moon to stabilize the axial tilt - sometimes tilts so far that it has equatorial ice sheets.
And - it's a long process also. On Earth it took millions of years.
THOUSAND YEAR LONG PROJECT
The Mars Society hope that with mega technology - giant space mirrors to reflect more light onto Mars to warm it up, and greenhouse gas factories and such like - that it could take as short a time as 1000 years - plus several more millennia to get the oxygen levels up.
But - is that what our descendants, 1000 years from now, will want us to do to Mars?
One thing that's clear - with those sorts of timescales, that we aren't doing it for ourselves.
For quite a few centuries it would be hardly changed. And all the way to the end of that 1000 years - you'd still need oxygen - and most of the time, need complete spacesuits to get around.
And - it's a high technology project, obviously, all the way through. So - will we maintain a high technology civilization for a thousand years to complete it? The people who want to terraform Mars often see it as a way for humanity to survive in case we lose our technology - but it's almost the opposite of that. You can't see it succeeding unless we keep a high level of technology for at least a thousand years and probably far longer than that.
UNTERRAFORMING
Then - once terraformed - it's going to gradually unterraform - the only question is how long it takes - at least - unless you keep supplying comets to replenish the atmosphere - if so - sustained long term megatechnology.
What seems pretty clear is - that nature won't just keep it terraformed for us automatically. What we see on Mars is the end result of Mars which might well have had life in the past.
And Earth's biological cycles, which keep Earth terraformed, won't work on Mars because of the cold, lower gravity, and long term - lack of magnetic field and continental drift.
I don't think that necessarily means it is impossible. But means that any solution to terraform Mars would need to take account of all these differences - and also need to look into the future - and decide - are we doing this for our descendants 30 generations from now? Or perhaps 30,000 generations from now if you allow an extra 100,000 years to build up an oxygen atmosphere on Mars?
If so - why? And will it matter for them that Mars would unterraform? What would the implications be for our descendants even further into the future, say a few 100,000 generations from now, as Mars loses it's atmosphere again and its water and returns to its current lifeless state, or some other state?
If we are doing this to help our descendants 30,000 generations from now, then we probably should also think about our descendants 300,000 generations from now.
I think we have a responsibility to those far distant people - who - well won't be exactly people as in that they will have evolved to new species long before then - but whatever or whoever they are - are stuck on a planet that we attempted to terraform which is gradually unterraforming around them - and may well have lost their technology by then.
It's an awesome thing to change the entire future of a whole planet - even if it does work. Especially also since - maybe if you set about things in a different way, using knowledge we don't have yet, but might have, say a century from now, maybe the whole process could be made far easier and take a shorter time to a better end result.
There is no hurry to get started on a 1000 year project, not if it is not yet totally clear that it's the best thing for us to do.
That needs to be thought through first!
And - lots of things to go wrong.
See my Trouble With Terraforming Mars
And
Imagined Colours Of Future Mars - What Happens If We Treat A Planet As A Giant Petri Dish?
But who knows - in the future maybe we might do projects like this. Not impossible, in a long stable civilization - and maybe with lifetimes extended, people living for tens of thousands of years etc etc, then you might get the understanding and knowledge needed to do stuff like this - and also to understand its consequences.
I think is great to think over ideas -but to actually attempt it now - especially - in some simple minded way just throwing microbes onto Mars and hoping they turn it into a copy of Earth - that's not going to work. And adding mirrors and greenhouse gases - again - just too crude, when we don't even understand how Earth works too well, and Mars is so different - and so much to go wrong.
(You've asked an almost identical question to this one Robert Walker's answer to Can any of the planets of the solar system be terraformed for human habitation? - so hope you don't mind I did a bit of copy / paste of my answer there, bit of light editing).
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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