LadyTevar wrote: ↑2022-12-22 05:31pm
bilateralrope wrote: ↑2022-12-22 11:32am
Then there is the issue of whatever makes Pandora's atmosphere toxic to humans. I forget what that is, so I'm not sure if it's from a biological or geological source.
Why can’t humans breathe in Pandora?
The high concentration of carbon dioxide in the Pandoran atmosphere makes it extremely poisonous to humans, rendering them unconscious in about 20 seconds and causing death in about 4 minutes when they venture out unprotected by specialized breathing masks.
In addition to the approximately 18% carbon dioxide there is also slightly greater than 1% hydrogen sulfide. Given that 800 ppm is the LD
50 for humans, and 1000 ppm causes immediate collapse and loss of breathing in a human being even 1% would be a big problem. It's also the reason the Pandora breathing masks cover the entire face including the eyes, as 1% is more than sufficient to cause eye damage in people.
In theory, more plants might bring down the CO
2 concentration to something humans can deal with (under 5%? Don't remember exactly), but that still leaves the problem of the H
2S. I'm not at all certain how you'd scrub that out of the air, and if you can't do that you'll never have large-scale terrestrial animal life. Maybe a massive seeding of bacteria/archae that utilize the chemical for energy, but I have no idea how long it would take for that to work, and some of those species don't tolerate oxygen, which Pandora also has in abundance.
I found it interesting that the only Pandoran life forms we see moving about in an Earth atmophere are either the Avatars or the half-Avatar children. Is that because the admixture of human traits gives them greater tolerance to Earth atmosphere? They still apparently need some sort of supplementation, but certainly they tolerate Earth air much better than humans tolerate Pandoran air.