Hadn't time to read, till today...
this seems pretty pointless:
u still insist on artificial terraforming, i though we settled this point SEVERAL posts ago.
Again, u seem to miss the scale. Again.
And primordial Earth - that should be enough: as we already established, elements doesnt transform, they chemically bound.
As you already correctly stated , living organism CAN transform(not in alchemic sense) atmosphere. As we know, it takes time...
Please check Hadean Eon, Archean Eon, especially about 4500 Ma. later on, there is so called late heavy bombardment, and procaryot evolution and so on and on.
Consider this SIMPLIFIED EXAMPLE... AGAIN (mind you its 3rd time i think that you ignored it, if u can disprove it, i will accept my defeat immediately:
1 'Primordial' atmosphere were unlivable for most known lifeforms.
2 Elements and they quantity on Earth are the same (except loss by regular atmosphere stripping and addition by cosmic dust/impactors)
3 Transformation of primordial atmosphere to anything usable for higher lifeforms happened on million years scale as far as we know.
4 It happened THANKS to existing living organism, which we should have...but it still took millions of years.
Scenario we were talking about, as i already stated, has basically 'primordial' conditions - as to our current knowledge - making it livable took millions of years AND specific lifeforms.
Why it should be that radically shorter this time around?
Even if we for sake of argument allow chemoautotroph lifeforms to survive, they still cant do miracles. Again, we were talking no artificial terraforming - no resources are expanded towards that goal, so they are subject to natural population/lifecycle/metabolic rate constriction. This has already happened here at least once before.
We are not talking Artificial Terraforming, we are not talking Major Exctinction Events, we are not talking puny Nuclear Winter.
I really hope that at least some of this STICK AROUND this time.
Frankly, i intended to source my arguments meticulously, but after a thought I deemed that futile...
Seems like Cyanobacteria, Great Oxygation Event(Catastrophe) and all implications are beyond your current knowledge. Please update before replying.
I admit, that shortest transformation of oxygenless atmosphere to free-oxygen(breathable) atmosphere takes theoreticaly 'only' about 2 000 years. But that is the most optimistic estimate based on best case scenario and CURRENT count of living organisms that can do that job, which is many times higher that it was at time...and probably that would be after planetary bombardment on scale we talk about :)
Standart timescale talks about timelag of about 300-900 mil years..
Even after rise of the atmospheric oxygen to about 1%, there were about a billion years of a 'stalemate' - almost no geological nor biological evolution..(ever heard of Boring Billion ? :) )
The next 100million years were the 'real' game-changer...(according to 2006 Bistability theory, which publication i missed at time )
but you should know all this, right?
Remember, i was quite GENEROUS in down-grading my theoretical scenario:
I dont insist on TOTAL life exctinction (would need to disrupt all surface few thousand meters in depth probably, anyway :) )
I kinda excluded all forms of physical/chamical energy release except kinetic and therefore associated contamination :)
Even your goverment volcano hazard source (although laughaubly puny considering scale IT TALKES ABOUT and scale WE TALK ABOUT) got link to http://volcanoes.usgs.gov/hazards/gas/climate.php .. give it a try, then multiply by millions... dont forget damaged ozone layer and other nice bonuses.. :)
It really does not go ANYWHERE near the scale we talking about - and again confirming my suspicions of you thinking nuclear winter and maybe small climate change...
I really hope your next post wont repeatadly ignore points I already stated several times, and the 'simplified example' with associated thoeries.
I really do hate repeating myself. [you cant begin imagine how painfull was this recycled post to write for me..dont wanna do again anytime soon]
< Message edited by MuthaF -- 7/21/2010 8:18:50 PM >