Traveller: World Stats: Atmospheres



key point: a lot of earth like worlds spent most of their time as

  • barren land, barren sea, CO2 atmos, no ozone, extreme radiation
  • barren land, microbial life bottom of the ocean, CO2 atmos, little ozone, high radiation
  • barren land, ocean life, very thin oxygen, low ozone, medium-high radiation
  • coastal land microbial life, thin oxygen, medium ozone, low-medium radiation
  • land life, ocean life, thin oxygen, high ozone, low radiation

which could be treated as

  • trace
  • very thin, tainted
  • very thin
  • thin, tainted
  • thin


Standard Atmosphere

Atmosphere 6 is the standard atmosphere which humans are adapted for and worlds with this type of atmosphere are denoted as Prime worlds.



Tainted can mean anything from a minor to a major problem. If a planet had a large population then it is generally minor. If a planet has a low population then it is probably major.


OTU Problem

In the CT world gen rules atmosphere type has no effect on population size and the original Spinward data and that data is based on the CT world gen I need a reason why type 6 planets weren’t favored while worlds with bad atmospheres can have billions of people.

IMTU Solution

In early exploration finding Prime worlds was the goal and other worlds were colonized simply as stepping stones.

However as Prime worlds are rare most of the humans in various forms seeking them out ended up spending centuries living in artificial domed habitats on all the worlds in between and people gradually came to see domed living as normal, if not preferable. By TL12+ most people prefer artificial habitats to natural habitats and live in domes even on atmos 6 planets. Only a minority of back to nature types prefer natural living. Hence preference is no longer given to Prime worlds only worlds with a good source of hydrogen and oxygen.

Alternative Solution

Change World Gen so atmosphere has an effect on population, something like:

population roll D6

atmos 0-3 DM-2
atmos 4 DM+2
atmos 5 DM+0
atmos 6 DM+4
atmos 7 DM+2
atmos 8 DM+2
atmos 9 DM+0
atmos 10+ DM-2

hydro 0-2 DM-2
hydro 3-4 DM-1
hydro 6-8 DM+2
hydro 9+ DM-2


Atmosphere Codes

0: vaccuum

1: trace

2: very thin, tainted

3: very thin

4: thin, tainted

5: thin

6: standard

7: standard, tainted

8: dense

9: dense, tainted

A: exotic

B: exotic corrosive

C: exotic insidious

(exotic: thin low, ellipsoid, dense high)



occasional list of exotic atmosphere types

Carbon Dioxide (Earth Archean Age)

warm & cloudy
atmosphere: carbon dioxide
seas: carbonic acid
lots of small continents
volcanic around the continent edges
lots of seas and lakes

rare raw materials around the volcanic rim?

domed and requiring manufactured oxygen and water but abundant sources of components

can be terraformed by adding photosynthetic microbes that will convert carbon dioxide to oxygen


atmosphere: chlorine

seas: hydrochloric acid

chorine based photosynthesis

yellow-green haze


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