The Orion's Arm Universe Project Forums

Chlorine photosynthesis on exoplanets
(04-07-2013, 09:29 AM)Matterplay1 Wrote: [snip]

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?

While it is very hard on atmospheric ozone, chlorine absorbs light with wavelengths shorter, IIRC, than about 420 nanometers; this would, depending on the abundance of chlorine in the atmosphere, offset the lack of ozone with regard to UV absorption. A redder star, producing less UV than Sol, might not provide a noticeable advantage in this regard, while restricting the range of useful planetary orbits.
The chlorine abundance of an atmosphere with a photosynthetic flora as described above is assumed to be about one percent (by volume); the amount of light blocked by this amount mightn't be very great, though I haven't done the calculations to check this.

"I'd much rather see you on my side, than scattered into... atoms." Ming the Merciless, Ruler of the Universe

Messages In This Thread
RE: Chlorine photosynthesis on exoplanets - by radtech497 - 04-07-2013, 09:14 PM

Forum Jump:

Users browsing this thread: 1 Guest(s)