Real Atmospheres

Real Atmospheres rebuilds the skies of Kitten Space Agency from physics. Every sky colour, haze and cloud layer is derived from that world's real composition and particle optics rather than painted in, so Mars glows blue at sunset, Titan's haze stacks into layers on the limb, and Pluto lights up with its blue ring as you swing behind it. About the screenshots: these were taken with a companion surface mod enabled, so the terrain you see on solid bodies like Pluto, Titan and Triton is not part of Real Atmospheres. This mod changes atmospheres, hazes and clouds; on those worlds the ground stays stock. The gas and ice giants are the exception: Saturn's, Uranus's and Neptune's colour maps are included here, at 2048 per face. The surface mod is not released yet, because it needs engine-side memory improvements before it can cover every body without running a graphics card out of VRAM, and it will follow once that lands.

Features

Mars * Rayleigh scattering derived from the real atmosphere: 95% CO2 at 6.1 mbar, faint and blue. * Dust as the colour engine, using Mie coefficients solved for feldspar and hematite Martian dust, so the sky colour comes from real dust optics instead of a tint. * The exact Mie phase function baked into the shader as a 361-sample table, with no Henyey-Greenstein approximation, producing the physically correct blue halo around the sun. * A compact, capped dust layer with a double-exponential vertical profile, giving the Curiosity-style blue sunset without an artificial limiter. * A high-altitude water-ice cirrus layer at 22 to 29 km: polar hoods and equatorial wisps, in both 2D and volumetric form.

Venus * Composition-true dense CO2 scattering at 53 times Earth's surface density, with a blue-selective absorber low down that drives the murky yellow descent to a Venera-dark surface. The fog comes out of real multiple scattering, not a fog term.

Jupiter * Composition-derived hydrogen and helium Rayleigh at the true 25 km scale height: a razor-thin blue limb over the cloud tops, the way Juno sees it. * Cloud decks rescaled to real altitudes, with storm structures 10 to 96 km tall and orbit transitions moved to match.

Saturn, Uranus and Neptune * Methane absorption as the colour engine: moderate for Uranus's pale cyan, which its thick haze mutes, and stronger for Neptune's deep blue, whose clearer air lets the colour through. * A faint blue limb above the haze on all three, with Saturn's puffy 52 km scale height derived from its low gravity. * Volumetric clouds, which none of the three had in stock: banded 3D structure with towers, coverage taken from each planet's own banding, and colour sampled from its own map so the clouds match the planet. * Higher-resolution colour maps at 2048 per face, up from 1024 on Saturn and 512 on Uranus and Neptune.

Titan * Stratified haze bands modulated into the scattering medium itself rather than painted on, so limb glow, phase and transmittance all stay physically correct. A per-pixel limb march gives them broken, undulating structure that the symmetric atmosphere lookup cannot hold, and they rotate and reshape over time, linked to the simulation clock. * Two detached haze laminae at 290 km and 230 km, each about 2 km thin, matching the individual layers Cassini resolved.

Pluto and Triton * Real nitrogen atmospheres: Triton at 1.5 Pa and 38 K, Pluto at 1.0 Pa and 40 K, with scale heights to match. Honest, and honestly almost invisible, like the real thing. * Forward-scattering tholin haze, the part you actually see. Pluto's fractal aggregates scatter roughly 1900 times more light forward than back, so the haze is invisible at full phase and then ignites into the New Horizons blue ring as you pass behind the planet. Triton does the same, more subtly. * Stratified gravity-wave haze bands rendered by a per-pixel march, with irregular spacing, dropped bands and varied widths, slowly drifting and reforming in sync with the simulation. * Patchy nitrogen-ice condensate clouds on Triton at 4 to 6.5 km.

Requirements

Real Atmospheres is a plugin for the StarMap mod loader, which you need in order to run it. This release is tested on KSA v2026.9.10.5438. It installs to about 105 MB, modifies no game files, and needs no admin rights: at launch it builds patched shadow copies of the relevant game content and redirects the game's reads into them.

Install 1. Install StarMap and run the game once through its loader. 2. Extract the zip into Documents\My Games\Kitten Space Agency\mods, so that you end up with mods\RealAtmospheres\RealAtmospheres.dll. The folder must be named exactly RealAtmospheres, because KSA uses the folder name as the mod id. 3. Launch the game once, then close it. KSA will have added the mod to Documents\My Games\Kitten Space Agency\manifest.toml, but disabled. Open that file and set the mod's entry to enabled = true. 4. Launch through StarMap. The log lists "found mod 'RealAtmospheres'" when it is active. To uninstall, delete the RealAtmospheres folder and the shared shadow folder the mod creates next to it, whose name begins with an underscore. KSA removes the manifest entry by itself.

Notes

How this was built: Real Atmospheres is vibe coded. The C# plugin, the shader patches and the Python asset pipeline were written by an AI assistant working to my direction, while I chose what to build, sourced the reference data and textures, tuned the look, and tested every build in game. The physics is taken from published measurements and papers rather than eyeballed values, and anything that did not hold up in game was thrown out.

This mod patches the game's atmosphere shaders. A future KSA update that reworks them can stop the game loading, usually at the "Loading shaders" step. If that happens, disable the mod until an updated release is out. The included README documents every change in detail.

Credits

Texture sources, all reworked into cloud masks, flowmaps and cubemaps for this mod: Mars cloud map by HMSMaidNelson, Saturn texture map by JCP-JohnCarlo, Uranus and Neptune texture maps by Askaniy, Titan haze and Triton cloud maps from SpaceEngine.