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Chlorine photosynthesis on exoplanets
(03-29-2013, 01:28 PM)radtech497 Wrote: [snip]
Since any life on the planet breathes oxygen and carbon dioxide (but can tolerate relatively high concentrations of chlorine), the biochemistry is at least vaguely similar; noticeably, carbon compounds will be somewhat chlorinated and will likely resemble plastics (an analogue of cellulose, for example, will be something like polyvinylchloride (PVC)).
All this chlorine in the atmosphere will react with any water on the surface to produce an aqueous solution of hydrochloric acid and hypochlorous acid. All bodies of "water," then, will be composed of a dilute acid and bleach solution. If chlorine gas comprises one percent of the atmosphere, this solution will have a pH of about 4.50 (similar to undiluted vinegar).
So, yes, chlorine and oxygen can coexist on a Gaian world, as long as the chlorine gas did not dominate the atmosphere.

Many of these issues got consideration in our existing Chlorine Worlds articles. Of course a difference from the scenario presented by the authors Steve quoted at the start of this thread is that the photosynthetic process I'd imagined is just a source of hydrogen ions & high-energy electrons, just as with known real-world photosynthetic processes that use something other than water as a hydrogen donor. Also, I'd not envisioned chlorocarbons as anything more than an incidental product. Another difference from the scenario the authors of the paper is that I'd imagined that a world with chlorine in the atmosphere would be more likely if the local star gives out less UV, not more. Halogens are very hard on the ozone layer, so if you want life to be able to survive on land or even in the upper photic zone of the oceans you might be better off with a star that is a bit redder than ours. A final factor which I didn't consider at first when I wrote the OA articles and which the authors Steve quotes might not have considered either is that chlorine is good enough at blocking visible light that even a small percentage of it in the atmosphere would make for a very dark surface. When I found that out I dialed down the percentages I mentioned, but honestly I don't know that I took it as far that direction as I ought. At some point I'll have to take the time to visit one of the local university libraries and read the full article. Has anybody else here seen more than the abstract?

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RE: Chlorine photosynthesis on exoplanets - by Matterplay1 - 04-07-2013, 09:29 AM

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