TRAPPIST-1 System by Cirax
This are my procedural planets for the TRAPPIST-1 Star. Four of them lay in the habitable zone (maybe more).
I focused the design in real data from Updated Masses for the TRAPPIST-1 Planets astronomical article April 2017. In it the estimated mean densities of the planets reveal that the three closest planets are rocky while the rest are near the density of the water making them oceanic or ice worlds.
To add some variety to the oceanic worlds (not just a covered oceanic plain and boring world) I changed the size of the ice layer a some minor differences.
You can download it from here:
To install just copy "TRAPPIST-1 Cirax.pak" inside the addons folder. Don't forget to rename the extension .pak to something else if you have another mod of the TRAPPIST-1 system.
The closest planet to its sun is heavily affected by the tidal effect from the star making it some kind of hot Io. It's a volcanic world with few craters and a young surface.
This planet is still too close to the sun and due it's estimated mass, (1.63 times the Earth mass) which allow it to sustain a great atmosphere, I supposed is a Venusian world.
In the design I wanted to reflect that in this kind of cloud covered worlds the surface is dark due the fact the clouds reflect most of the light that would come to the surface, so I added another dark cloud layer under the bright one (to add a cloudy effect), darkened a lot the atmosphere but also making it less opaque.
Resuming, from the space the planet looks like Venus (a bight world) but if you land the surface and the sky is dark and the atmosphere is more transparent.
This rocky world stays close to the habitable zone, the central part of the planet is hot and devoid of any liquid water but in the terminator zone the temperatures are warmer allowing the presence of liquid water. In that zone I placed a big sea and some big lakes and rivers.
This covered water world has a floating ice layer over it in the nocturnal face. The warm water of the surface coming from the tropics melts part of the ice breaking into the dark side of the globe.
A mix between an ice world and an oceanic world TRAPPIST-1 f has a thick ice floating layer. When the ice gets close to the warm zone breaks into icebergs that continue its travel to the centre of the ocean where the higher temperatures melt them.
Only in the latitudes directly under the sun rays the ice gets melted in TRAPPIST-1 g, the most of the world is covered by the ice. In this case I imaginated that because it's superior mass compared with its oceanic brothers (plus the tidal effect still relevant) its interior is more active meaning that some hot water emerge for the deeps and melts some parts of the ice layer creating temporally lakes or breaking the ice making this cracks looking like rivers.
The last planet (right now) of TRAPPIST-1 is just an iceworld. There is no liquid water in the surface, it's crossed by multiple cracks and has some craters. Under the ice layer it could be a liquid water ocean warmed by the hotter mantle.
That's all, and sorry for my "barbarian" english