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Question

Obviously Earth's atmosphere is just fine for life it, but is there a possibility of one composed of gases that would make life have an easier time living? If yes, what would it consist of?

My idea

I have a rough idea of something along those lines:

-1.5 atm pressure- with denser atmosphere, flying creatures should have easier time staying afloat

-around 30% Oxygen concentration- below 0,5 bars of partial pressure, so that humans won't get intoxinated, but still would be able to breathe more efficiently

-Carbon Dioxide concentration between 0,5% and 0,1%- to let plants generate more energy via photosynthesis

-higher concentrations of water vapour- due to higher temparature and atmospheric density, more water vapour could "fit in", allowing moisture to get transported further inland than on Earth

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  • $\begingroup$ A higher oxygen content would allow insects to be larger as happened during the Carboniferous and Permian periods. $\endgroup$
    – user81881
    May 14, 2022 at 8:35
  • $\begingroup$ Higher oxygen content also makes combustion easier and faster, which is generally not ideal for humans. $\endgroup$
    – Cadence
    May 14, 2022 at 9:03
  • $\begingroup$ @Cadence Unless you'd use it for your benefit, for example jet engines $\endgroup$
    – Yulian
    May 14, 2022 at 9:17
  • $\begingroup$ @Yulian The way the fuel/oxygen ratio impacts engines is a bit complex but in general, getting enough oxygen is not the problem; indeed excess oxygen can be a huge drawback (it leads to much higher temperatures). This is doubly true for jet engines which already only combust part of the air they ingest by design. $\endgroup$
    – Cadence
    May 14, 2022 at 9:47
  • $\begingroup$ @Cadence The design could always be changed, especially considering the fact, that humanity arriving on this planet would regress technologically and would have to reinvent modern-era advances, making them adapted to new environment, possibly exploiting it for greater efficiency. $\endgroup$
    – Yulian
    May 14, 2022 at 9:54

2 Answers 2

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Hot and Humid

enter image description here

The rainforest is full of life. Let's crank up the heat and humidity and go back to a planet covered in primeval jungle.

Rainforests like the heat. Raise greenhouse gas levels to up the temperature. Sea levels will rise and wash away those pesky humans. But life finds a way.

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  • $\begingroup$ That's what I was assuming. And humans will be just fine, they'll arrive on the planet when these changes will occur, not before them. Is there a way to calculate the greenhouse effect though? $\endgroup$
    – Yulian
    May 14, 2022 at 14:52
  • $\begingroup$ @Yulian If it's not Earth we're talking about, there is no need to worry about the greenhouse effect to heat the planet. Just put the planet closer to its sun or use a bigger sun. $\endgroup$
    – Daron
    May 14, 2022 at 14:54
  • $\begingroup$ Can't do, I'm basing my planet on Kepler-452b, I got physical parameters for the star and orbital parameters for the planet. Everything which cannot be observed (or which has a big margin of error, like mass of the planet) is where I took some artistic liberty. $\endgroup$
    – Yulian
    May 14, 2022 at 16:01
  • $\begingroup$ @Yulian You could either assume everything else is Earth-like and then compare charts of atmospheric C02 and average Earth temperature. Or you could assume there is enough "everything else" parameters -- atmosphere depth, sea coverage, icecap size -- that you don't need to do exact calculations. Just say 0.1% C02 is the right amount for this planet, whether or not it is the right amount for Earth. $\endgroup$
    – Daron
    May 14, 2022 at 16:29
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    $\begingroup$ @SeanOConnor Oh you mean like 3/8 of flip-all $\endgroup$
    – Daron
    May 18, 2022 at 12:08
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That much CO2 is going to create an amazing greenhouse effect, roasting any life you will have on Earth.

More generally speaking, there is no proof that higher CO2 concentration is beneficial to plants, else we should have already seen it since the start of the industrial revolution.

And, as you said, life is optimized around the composition of our current atmosphere. Changing it is going to screw up somewhere.

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  • $\begingroup$ I'm aware of the grennhouse effect, concentration of CO2 would compensate for smaller solar power arriving on the surface and would be the main cause of this planet entering an interglacial. Edit: Regarding CO2 and plants, I heard somewhere (won't pin point the study), that the wild vegetation and average size of the leafs had been increasing as the concentration of Carbon Dioxide has been increasing. I might be wrong on that though $\endgroup$
    – Yulian
    May 14, 2022 at 9:19
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    $\begingroup$ "Else we should have already seen it since the start of the industrial revolution": We do see it and we are actively doing it. In glasshouses, of course. "The benefits of carbon dioxide enrichment to about 1100 parts per million in greenhouse cultivation to enhance plant growth has been known for nearly 100 years." (Wikipedia) $\endgroup$
    – AlexP
    May 14, 2022 at 14:08
  • $\begingroup$ @AlexP sure, greenhouses where somebody supplies all the rest that a plant needs to benefit from the higher CO2 content. Who does that in the wild? $\endgroup$
    – L.Dutch
    May 14, 2022 at 14:33
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    $\begingroup$ It is somewhat difficult to practice CO2 enrichment in open air... $\endgroup$
    – AlexP
    May 14, 2022 at 15:13
  • $\begingroup$ All other things being equal, more CO2 is beneficial to crop yields. That's consensus. The part that gets controversial is how much it offsets climate change. nasa.gov/feature/goddard/2016/… $\endgroup$
    – user86462
    May 15, 2022 at 10:16

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