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I'm effectively looking to change the 'Could' in this question to a 'what' or 'How'.

Could higher land-based life exist on a planet with a pressure of about 1 MPa?

I'm working on a story in which humans visit a planet with intelligent life present. This will be an ammonia world, with a comparable gravity to earths, but a larger atmosphere: say, 10 atmospheric pressures.

The humans will/can be wearing whatever is necessary to keep them alive (breathing apparatus etc).

I'm wondering what the effects will be of this atmosphere?

1) I read about heat transfer- is this going to a huge problem for any life or humans on this planet? I understand that the heat would be sucked out of the animals very quickly, maybe prohibitvely quickly.

2)what would it feel like for a human? like being underwater? and could humans potentially fly at this pressure (easily, with the aid of some mechanical costume?)

Also other considerations, like how sound and light propogate? Sound will be a lot quicker, and I assume that the light level at the surface will be much lower (How much lower?) would sound become a much more important tool than sight for animals evolved on this planet?

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    $\begingroup$ An ammonia world implies a reducing atmosphere (vs. Oxygen surplus); I think that will be a much bigger change (from known life) than a mere 10x increase in air pressure. What sort of biochemistry are this planet's lifeforms using? $\endgroup$ – Catalyst Mar 1 '17 at 13:11
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    $\begingroup$ The creatures would use ammonia as a solvent in place of water, but still be carbon based. $\endgroup$ – princeprince Mar 1 '17 at 13:13
  • $\begingroup$ I should have asked, 'how do these ammonia-using lifeforms get energy?' They cannot oxidize/reduce carbon with oxygen, because there isn't any free. (Atmospheres are virtually always either oxidizing {like ours} or reducing {like Jupiter, with all that ammonia and methane.) How do your aliens metabolize?? $\endgroup$ – Catalyst Mar 1 '17 at 13:30
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    $\begingroup$ 1 ATM causes an air pressure of 14.7 psi so this atmosphere would cause 147 psi. Every square inch of your shoulders would have 140 pounds pushing down on it at sea level $\endgroup$ – Landon Boyd Mar 1 '17 at 14:30
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I read about heat transfer- is this going to a huge problem for any life or humans on this planet?

No idea objectively. Probably yes.

What would it feel like for a human? like being underwater?

The intense pressure would certainly create a feeling of underwater experience on Earth. However, although limb motions would experience much higher levels of drag, that would be nothing like underwater slow-mo.

Without pressure reduction suits, a normal Earthly-human would get ear pains very soon, followed by nausea and headache. Also, the freely available ammonia in the atmosphere will have devastating effects on the eyes, the lips, the inner lining of the nose and other places with soft membranes. It would feel like taking a dive in an ocean of bleaching powder. Extremely displeasing and very dangerous.

And could humans potentially fly at this pressure (easily, with the aid of some mechanical costume?)

Yes. While flight (with the help of wide leather/metallic flaps, worn on arms and legs) would still take a lot of muscle power, it will definitely be possible to stay aloft. Flight, for humans, will take the effort of both arms and legs and will require muscle movement resembling swimming.

Would sound become a much more important tool than sight for animals evolved on this planet?

This depends, not only on the composition of the atmosphere, but also on the distance of the planet from its star, the luminosity of the star and of course, the type of eyes these creatures possess. For example, for an Earth-sized planet present at 1 AU from its G type star, there would still be enough light reaching the surface for normal vision (albeit the excessively bleaching effect of the ammonia atmosphere on the eyes).

My personal idea about the environment (I have not researched this in detail) is that the creatures will require a very sophisticated ear type to function well on this planet. Human and other mammalian ears would be picking up too much noise and amplified sounds all the time to function properly. Smart noise filtration would especially be required.

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