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Several plans to terraform use the abundant amounts of CO2 as a means of thickening the atmosphere, by outgassing etc...
So once the atmosphere is thick enough, and there is a start of creating oxygen, using photosynthesis, there should be a way to reduce the CO2 amount to lower levels, to make the atmosphere breathable...
Thicker CO2 atmosphere would mean large volumes of open water, and these could be used as CO2 sinks, by introducing [http://earthobservatory.nasa.gov/Librar … thophores/]Coccolithophores if i'm not mistaken? In the short term CO2 levels would actually go up, but eventually more of it will get bonded into CaCO3, and sink down, forming sediment.
(flashback from a "spreekbeurt" (dunno the 100% right English word: lecture engagement?) i gave for the class when I was 14... about the Gaia theory, wich blew my socks of at the time, heehee!)
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I believe that planktonic capture of CO2 in the eventual form of limestone is one of the major carbon sinks on our planet. Regular old temperate forests can also act as a carbon sink. This is especially true if you don't allow the wood to rot. If wood is used as building supplies, the carbon is tied up out of the atmosphere. (this is not to say that we should start cutting down trees and burying paper in landfills to fight global warming but it *would* help)
The Gaia theory is neat but pretty much no one, not even its creators believe in it anymore. It's pretty clear that life doesn't modify its environment to suit it unless by chance. The history of life on this planet is a lot like our own - lurching from one near disaster to another by luck as much as anything else.
For example, plants nearly wiped life on this planet out twice. The first was when they started making oxygen, converting our atmosphere from a reducing to oxidizing environment and just about killing everything inthe process. (the original toxic waste dumpers) The second was when plants developed cellulose which other organisms coudln't break down. As a result, gigatons of carbon were locked up in dead plants and not recycled to the atmosphere. There is some tenuous evidence that the Earth actually went into a massive ice age for several million years where the oceans froze to a depth of a mile and the planet did its best Mars impression. Life would have been largely wiped out had it not been for tectonic activity causing volcanos to start bringing the CO2 levels back up. Eventually, microbes developed the ability to break down cellulose but an enormous amount of carbon was lost in the meantime. It's believed that most of our hydrocarbon deposits are the result of that episode and that we're now reintroducing 'missing' carbon that fell out of the biosphere 500 million years ago.
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Yes, I am aware of the problems with the Gaia theory... Now. As I said, i was 14, then, 20 yrs ago, so easily impressed and all that.
Still, somewhere i read that *parts* of Lovelock's theory are nowadays more widely accepted in the scientific community (but it didn't say wich parts, HAH)
Essentially the no-tectonics on Mars would be a mayor show-stopper for Gaia, even if it were a 100% valid theory...
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I think the whole idea of a biological ecosystem working in concert like a single organism in some ways if fairly well accepted in spirit if not in letter. BTW, Lynn Margulis co-wrote a book a few years back called Five Kingdoms which I own and is quite good. It basically spends a page or two on each pylum of life - there are hundreds. The best part is that out of over 400 pages, 4 are devoted to the phylum craniata (chordates including everything from apmphibians up to us). Almost all of the book is filled with single celled organisms, including some truly bizzare ones.
A favorite are the Archaeprotista - giant protozoa with no mitochondria and hosts of symbiotic bacteria living inside of them. It's not clear if the symbiosis is something recently evolved or if these are living fossils of the original proto-eukaryotes. These are the organisms that digest wood in termite guts amongst other things. One genus is large enough to see with the naked eye (~200 microns long)!
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Archaeprotista... Those are the infamous methane errr... producers?
How come they think it might be a recently evolved symbiosis? Or better phrased: what do they mean with recent? Archae that are 'new'... Sounds strange to me...
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By 'recent' that could mean any time in the last billion years or so. Evolutionary biology regularly deals with time periods that astronomers usually use. By recent, I meant a symbiosis that had occurred after the original symbiotic arrangement that resulted int he formation of eukaryotic life like us.
These are the methane producers. The symbiotic bacteria living in them are often methanogens. The giant mibrobe I mentioned has no fewer than 3 seperate species of symbiotic bacteria in it, two of which are methanogens. Giardia of backpacker's woe is also a member of this phyla.
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Thanks, I thought 'recen' was millions of years, sigh...
So Archea at the outside, hosting 'modern' bacteria in the inside... Hmmm. Indeed interesting critters.
I wonder, but that's probably unanswerable, how they survived w/o their modern symbionts...
Wild guess: They didn't need them, because there was no cellulose to process? They lived on 'simpler' stuff, maybe in symbiosis with arhea'bacteria' (i know: contradiction in terms?) Once cellulose material became over-abundant, as you pointed out earlier...and some bacteria evolved to break it down, a host would reap the benefits, food aplenty...
Disclaimer: Just *very* wildly guessing-speculating, I'm a total dilletant, so nnever mind my mindless jabbering (if that's the right word...)
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It could have been millions of years - I don't know. It imght be possible to find out but AFAIK, research on these critters is pretty low key with few people in the field. There's entire branches of life on this planet with only a handful of underfunded researchers devoted to them.
The simplest explanation is that these were originally protozoan with little to no organelles (many organisms in this phyla don't have things like mitochondria and golgi bodes.) At some point they somehow entered into a beneficial relationship with bacteria that could do things like digest cellulose. Over time, the two orgamisms evolve so that they are dependent upon each other. Many archaeprotista die if you use antibiotics to kill the bacterial symbionts.
Most of out own organelles like mitochondria, golgi bodies, nuclei and chloroplasts (in plants) are believed to have come from a similar mechanism. What's unclear is if these archaeprtosta are simply more recent symbiotes or actually an unchanged variant of the original eukaryotic reatures from 1-2 billion years ago that all higher life came from.
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