Stella Dei currently has many mechanics, none of which use any real physics unit, thus those should be converted:

• Planet radius (preferably express it in km, currently most values are expressed relative to it, with 1 being the radius of the planet)
• Temperature (already expressed in Kelvin)
• Physically accurate temperature behaviour
  • Conduction
  • Thermal radiation
  • Solar illumination
  • Any other non-negligible phenomena affecting temperature in a way that a basic simulation (liquid water + poles on north and south) can't work without that
• Water elevation (preferably express it in km)
• Physically accurate water behaviour (that is, as a flat layer like it is currently, as particle simulation would take too much computing resources and be mostly useless)
• Decide of what materials the planet is made of, in which layers and in which quantities

Once all of those are done, progress on other features may continue.

They will create craters and add resources (sulfur and water vapor in the atmosphere)
If the planet has a thick enough atmosphere, meteorites won't reach the surface

Eventually, an atmosphere should be added which would interact with #1 by having organisms use CO2 to produce O2 and have reactions with other gases (deadly gases, etc.)
The following gases should be implemented (more to come): Oxygen (O2), Carbon Dioxyde (CO2), Water Vapor (H2O)

• Implement gases with pressure represented as N extruded spheres at different levels of altitude (N is to be determined)
• Add Oxygen
• Add Carbon Dioxyde
• Add Water Vapor
• Add an optional visualisation of those gases pressure (similar to the way we can see the surface's temperature by pressing middle mouse)
• Clouds?

Add basic life forms like prokaryotes and eukaryotes that would proliferate in the water.
For that we need to:

• Think of a way to visualize single-celled organisms that wouldn't cause you nightmares when there are too many of those
• Think of a way for life to start (meteor?)
• Implement basic nutriments which will have different densities in the water
• Add cyanobacterias which consume CO2 + sunlight and make O2

When using an icosphere with 7 or 8 subdivisions, the main bottleneck in the render thread is Planet.upload, due to the nature of the method, it could easily be moved to a geometry shader which would relieve the CPU and probably make the process faster.

It would show a semi-detailled history of life and geology on the planet. With a book where every important event would correspond to one line.

That is, for every 6 tiles, there would only be 1 air velocity, 1 vapor pressure level, etc.
This can reduce simulation costs by 6x while having minimal effect (given wind can be simulated at a larger scale)