I’m wondering if anyone has any scientifically plausible ideas for adaptations to a high atmospheric pressure (10 atm) environment. This pressure would be too high for humans to survive for extended periods. Assuming a high partial pressure of nitrogen, how might animals on this planet evolve to avoid nitrogen narcosis? How might they adapt to high oxygen and CO2? I’m making a fake science textbook/art book about habitable planets, so I’m hoping to provide plausible, science-based explanations. Would it make sense for animals on this planet to simply have a more limited surface area for gas exchange?
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Ten atmospheres is not going to require any serious changes in size, area, or volume. The primary changes that will be required are concentration setpoints.
Breathing involves exchange of gases. Oxygen in and CO2 out. The process has a fairly wide range of operation. If you need more oxygen you can breathe harder. If you were in conditions where you needed a lower volume of gas to get the O2 you needed in and the CO2 you needed to get rid of out, you could just take fewer breaths per minute.
Our health depends on the concentration of O2 and CO2 staying within certain limits. If you let either go out of range you start to have negative health effects that get rapidly worse the farther out of range.
I do not know what the relative efficiency of gas exchange is at the higher pressure. But suppose that the exchange of O2 and CO2 changed by different factors. In order to keep them both in the healthy limits it might be required to adjust the relative efficiency of the lungs for O2 and CO2. It might require a tweak to the content of the blood so that one of these was more or less soluble. Or it might require a tweak of the membranes in the lung that the gases pass through. Or it might require a tweak of the healthy range of either O2 or CO2.
These are all relatively minor tweaks. From the outside the changes would not be obvious.
The adapted individuals would need to stay pretty close to their adapted pressure.
Interestingly, some organisms have been observed to survive at much higher pressures. You asked about 10 atmosphere, which is 1 MPa. This paper notes that organisms have survived into the 1000 MPa range in labratory conditions.
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I added the following after getting 2 up votes.
There is another aspect of living at 10 atm. That is nitrogen narcosis (NN). 10 atm is the equivalent of about 100 meters depth in diving. NN can begin to appear at depths of 30 meters, and can progress with depth.
In humans, NN can manifest in a variety of ways. But it often manifests first as loss of mental acuity, giving rise to the name. It is like being drugged. As symptoms advance it becomes more pronounced. Eventually it can lead to coma. Lack of control on the part of a diver is usually the source of injuries rather than the NN itself. Symptoms resolve minutes after returning to the surface.
The exact mechanism whereby NN affects people is not known. There is some thought that it affects cell membranes. There are a number of organisms that live their entire lives at depths of more than 100 meters, so it can certainly be alleviated through some kind of adaptation. This would probably be a question of differential absorption of nitrogen in the affected parts. But, as with normal breathing, it is unlikely to be visible from the outside.
