For ease of both myself and others I have calculated the terraforming costs and perfect atmospheric balance for all four colonizable bodies in Sol. All calculations made are based on the standard human colony costs. I took care to calculate in the maximum oxygen percentage, temperature values (taking 10 degrees Celsius as a goal temperature) and minimize effort.
General Notes:
Calculating the necessary amount of (anti-)greenhouse gases is always my first step, given that N2 and O2 will not have a significant impact on the temperature.
I use CO2 as greenhouse gas. You can replace it with Safe Greenhouse Gases.
I use N2 to ensure that the percentage of O2 is below 30%.
I aim for 28% in my calculations when the percentage of O2 would become too high.
I always use 0.105 atm of oxygen.
CO2 - 0.227 atm (~61%)
O2 - 0.105 atm (~28%)
N2 - 0.043 atm (11%)
Total: 0.375 atm
Total changes in atmosphere: 0.365 atm
Effort: Minor
Notes: None
AGHG - 0.670 atm (~86%)
O2 - 0.105 atm (~14%)
Total: 0.775 atm
Total changes in atmosphere: 0.775 atm
Effort: Moderate
Notes: AGHG stands for Anti-Greenhouse Gasses
CO2 - 3.000 atm (~97%)
O2 - 0.105 atm (~03%)
Total: 3.105 atm
Total changes in atmosphere: 4.705 atm
Effort: Significant
Notes:
- Terraforming will be incomplete.
- End Temperature will be ~229.8 K or -43,2 C.
- For colony cost 0 a modified species will be needed.
CO2 - 0.146 atm (~39%)
O2 - 0.105 atm (~28%)
N2 - 0.124 atm (~33%)
Total: 0.375 atm
Total Changes in atmosphere: 99.835 atm
Effort: Practically Impossible
Notes: A fully terraformed Venus might be the pride of the empire.
Please note that I am not trying to insult anybody by explaining the mathematics behind my calculations. I am trying to make it as clear as possible, even for those who would otherwise not understand algebra.
You can use my methods yourself if you wish to calculate the colony costs of any other planet (for example: In another solar system).
We will use these formulas:
Base Temperature in Kelvin x Greenhouse Factor x Albedo = Surface Temperature in Kelvin
Greenhouse Pressure = [Greenhouse Factor - 1] / 1.1 OR Greenhouse Pressure = [Greenhouse Factor - 1] / 0.9
The first formula is for when the body is colder than you want. The second formula is for when the planet is warmer than you want.
This formula substitutes the default. Basically every 1 atm of greenhouse pressure counts as a Greenhouse Factor of 1.1 because of the fact that it is ALSO Atmospheric Pressure.
Greenhouse Factor = 1 + (Atmospheric Pressure /10) + Greenhouse Pressure (Maximum = 3.0)
Note that the maximum Greenhouse FACTOR is 3.0.
We will substitute Greenhouse Factor with Z, and Greenhouse Pressure with Y.
Let's say we take Mercury for an example.
Our goal surface temperature is 283 degrees kelvin (10 °C).
The Base Temperature and Albedo are found on the environment tab.
We will want to know the necessary Greenhouse Factor.
700 x Z x 1 = 283
700Z = 283
Z = 283/700 = 0.404
We have calculated our necessary Greenhouse Factor. We can now add this data to the other formula.
The planet is HOTTER than we want, so we will take the / 0.9 variation of the formula.
Z = [0.404 - 1] / 0.9
Z = [0.596] / 0.9
Z = 0.67 atm of anti-greenhouse gases.
Note: We can not have a negative amount of gases. Thus we took an absolute value and removed the minus.
We will also need 0.105 atm of O2.
Our final step is to see if we exceed the 30% oxygen mark.
Basically, if the total atmospheric pressure is above 0.375 we do not exceed the 30% maximum.
We can also calculate the percentage of oxygen:
O2 (atm) / Total Pressure (atm) x 100 = Percentage of oxygen in the atmosphere.
It is the same for all other gases.