Let's create an alien biosphere!

[MathAndCode]

Then we should figure out how long it takes for the substances in the atmosphere to deplete. We don't have to be too exact. We could maybe make it 100-300 million years? I don't know.

It would probably take longer than Earth due to the thicker atmosphere and other factors.

[Schiaparelliorbust]

It would probably take longer than Earth due to the thicker atmosphere and other factors.

Do you have any estimates for Earth then?

[MathAndCode]

Do you have any estimates for Earth then?

https://en.wikipedia.org/wiki/Great_Oxi ... -atm-2.svg

[Schiaparelliorbust]

https://en.wikipedia.org/wiki/Great_Oxi ... -atm-2.svg

I know that one, but we need estimates for extra atmospheric gases.

[MathAndCode]

I know that one, but we need estimates for extra atmospheric gases.

I wouldn't worry about that very much. Gases that wouldn't have been common in Earth's pre-oxygen atmosphere don't constitute large fractions of the alien planet's atmosphere.

[Schiaparelliorbust]

I wouldn't worry about that very much. Gases that wouldn't have been common in Earth's pre-oxygen atmosphere don't constitute large fractions of the alien planet's atmosphere.

So you're saying that the presence of the other reducing gases won't affect oxygen much? I'm okay with that as long as it's realistic.

[MathAndCode]

So you're saying that the presence of the other reducing gases won't affect oxygen much? I'm okay with that as long as it's realistic.

They'll probably deplete about as much oxygen on average anyway.

[Schiaparelliorbust]

They'll probably deplete about as much oxygen on average anyway.

Should we worry about the byproducts of the reactions between oxygen and the other gases?

[MathAndCode]

Should we worry about the byproducts of the reactions between oxygen and the other gases?

The end products will be water, carbon dioxide, dinitrogen, and sulfuric acid. Each is already present in the atmosphere to some extent.

[Schiaparelliorbust]

The end products will be water, carbon dioxide, dinitrogen, and sulfuric acid. Each is already present in the atmosphere to some extent.

Since the atmosphere is slightly more larger and the presence of the reducing gases, I think we can make the initial oxygenation stage around 350-400 million years. (On Earth it was 309 million years). How do we calculate the diameter of a planet based on its gravity? I can't find anything online.

[MathAndCode]

How do we calculate the diameter of a planet based on its gravity? I can't find anything online.

Did we not decide the planet's diameter relative to Earth separately?

[Schiaparelliorbust]

Did we not decide the planet's diameter relative to Earth separately?

I don't remember doing that. Wouldn't the radius and gravity by connected?

[MathAndCode]

I don't remember doing that. Wouldn't the radius and gravity by connected?

The gravity would also depend on the planet's density.

[Schiaparelliorbust]

The gravity would also depend on the planet's density.

Wouldn't we just be able to use the gravity to figure out the density and diameter of the planet? Isn't that what Biblaridion did with Artifexian when they were making theirs? The formula they used is g = m/r² = r(ρ). I don't know what that last pat means.

[MathAndCode]

Wouldn't we just be able to use the gravity to figure out the density and diameter of the planet? Isn't that what Biblaridion did with Artifexian when they were making theirs? The formula they used is g = m/r² = r(ρ). I don't know what that last pat means.

The last part means radius multiplied by density.

[Schiaparelliorbust]

The last part means radius multiplied by density.

That just makes it look like a function. I also don't know how to calculate the rest of the variables, I need to know the value of at least one more. In the video they make the planet have the same diameter as Earth. That could work for us.

[MathAndCode]

That just makes it look like a function. I also don't know how to calculate the rest of the variables, I need to know the value of at least one more. In the video they make the planet have the same diameter as Earth. That could work for us.

Yes, but then the density would have to be larger, and Earth's density is already at the high end for terrestrial planets. I think that keeping the density the same and increasing the radius would be more realistic.

[Schiaparelliorbust]

Yes, but then the density would have to be larger, and Earth's density is already at the high end for terrestrial planets. I think that keeping the density the same and increasing the radius would be more realistic.

Ok, I didn't know that, thanks for telling me. Then the equation would give us 120% Earth radius and gravity with 172.8% Earth mass.
Edit: And consequently 72.8% more maximum atmosphere.

[MathAndCode]

Ok, I didn't know that, thanks for telling me. Then the equation would give us 120% Earth radius and gravity with 172.8% Earth mass.
Edit: And consequently 72.8% more maximum atmosphere.

The volume of the atmosphere would be equal to the surface area of the planet multiplied by the atmosphere's thickness. The surface area would be 72.8% greater, but a planet with more gravity would probably be able to gravitationally ensnare more gas molecules, resulting in a thicker atmosphere.

[Schiaparelliorbust]

The volume of the atmosphere would be equal to the surface area of the planet multiplied by the atmosphere's thickness. The surface area would be 72.8% greater, but a planet with more gravity would probably be able to gravitationally ensnare more gas molecules, resulting in a thicker atmosphere.

Yes, I posted that edit without quite thinking. Also, the surface area would be 1.44 times greater.

[MathAndCode]

Yes, I posted that edit without quite thinking. Also, the surface area would be 1.44 times greater.

How much thicker do you suppose that the atmosphere would be?

[Schiaparelliorbust]

How much thicker do you suppose that the atmosphere would be?

Thickness I guess that would depend only on gravity, but volume would probably be the product of surface area and gravity.

[MathAndCode]

Thickness I guess that would depend only on gravity, but volume would probably be the product of surface area and gravity.

So you think that the thickness would be proportional to the surface gravity?

[Schiaparelliorbust]

So you think that the thickness would be proportional to the surface gravity?

Yes. I don't think altitude differences for gravity will matter much. Gravity is still 0.9G up at the ISS. Also, height will probably be the determining factor for oxygenation rates because as you said before photosynthesizers and atmospheric volume are both proportional to surface area, whereas only thickness is proportional to gravity.

[MathAndCode]

Yes. I don't think altitude differences for gravity will matter much. Gravity is still 0.9G up at the ISS. Also, height will probably be the determining factor for oxygenation rates because as you said before photosynthesizers and atmospheric volume are both proportional to surface area, whereas only thickness is proportional to gravity.

So in that case, I believe that atmospheric volume will be proportional to the planet's mass—unless the atmosphere would be more dense in planets with higher surface gravity.