Hi everybody, I've created a tool for generating star systems that gives atmospheric composition for each planet. It gives pretty realistic results while also providing some surprises. The Cosmos-2 ruleset I found here played a large part in the generating the other properties.Quotient Ring
You'll find an extensive discussion of its development on the website, but I'll say roughly how it works here.
* Start with a homogenous gaseous mixture of selected compounds rather than elements, at reasonable concentrations, distributed uniformly over the surface of the planet. These are our working volatiles. Some will eventually escape or condense out depending on temperature and pressure.
* Decide randomly whether there is life present. If so, choose at random one compound that is known to be reactive. Also choose any other compound or element. The reactive compound will be kept out of equilibrium at a relatively high concentration, and the other will be kept relatively scarce.
* Decide on the overall mass Mvol of the body of volatiles. We'll use this as an initial value for the atmospheric mass Matm.
* Determine the planet's equilibrium temperature Teff with respect to incoming radiation from the star.
* Run this loop until the atmospheric properties are near equilibrium:
* Eliminate components whose molecules have too high an escape velocity.
* Update Mvol and Matm accordingly.
* Compute the surface temperature. Include the effects of condensates and greenhouse gases.
* Compute the surface pressure from Matm and the planet's surface area.
* Determine the abundance of seas, clouds, and frosts for use in the next iteration.