Master of Orion Wiki

Biomes are the environment of a given planet, determining nearly everything about its usability from food production to industry. They range from idyllic Gaia-class planets to hellish Toxic or Volcanic death worlds.

Nearly all Biomes can be upgraded in one way or another, improving their habitability.

List of biomes[]


  • The cells percentage is simply the maximum amount of cells available for the relevant purpose on the given biome type. A planet's total number of cells is divided in two, half for agriculture and half for industry. The percentage shows how much of these cells are actually usable. For example, a large world has 20 cells, so it has 10 farmable cells and 10 productive cells. A terran world has 80% farmable and 70% productive, meaning 8 farmable cells and 7 productive cells. (Science cells are not limited.)
  • Terraforming and transformation projects move the planet up one class. Pollution, if not cleaned up, will degenerate a planetary biome one class down once it reaches 100% (eg. a Terran B-class planet becomes a Swamp or Arid C-class planet).
  • With the Unofficial Code Patch, pollution absorption also depends on planet size. It is 60% of given value for tiny planets, 80% for small, 100% for medium, 120% for large, and 140% for huge.


Type Image Class Base Food per cell Farmable cells factor Productive cells factor Pollution absorption
Planet radiated.png
E 0 0% 55% 500
Planet toxic.png
E 0 0% 55% 500
Planet volcanic.png
E 0 0% 60% 500
Planet barren.png
E 0.5 32% 55% 60
Planet desert.png
D 1.15 40% 60% 40
Planet tundra.png
D 1.35 45% 65% 40
Planet arid.png
C 1.6 55% 70% 40
Planet swamp.png
C 2 65% 70% 40
Planet ocean.png
B 2.5 75% 60% 40
Planet terran.png
B 3 80% 70% 40
Planet inferno.png
B 0 0% 100% 100
Planet tropical.png
B 3.5 100% 100% 40
Planet grassland.png
B 3.5 100% 100% 40
Planet cavernous.png
B 3.5 100% 100% 40
Planet gaia.png
A 4 100% 100% 40

Special biomes[]

Type Image Notes
Antaran ruin
Antaran ruin.png
Non-colonizable. Between four and seven of them will be spread throughout the galaxy. Building asteroid laboratories on three of them and keeping them for at least ten turns allows to build the Antaran portal generator.
Asteroid field
Non-colonizable except by pirates. Asteroid mines and labs can be built on them. They can be coalesced large or huge Barren planets with a Space factory Planets destroyed by a supernova or with a Stellar converter can be coalesced into a Barren planet of the size of the original planet .
Gas giant
Planet gas giant.png
Non-colonizable. Superscalar gas harvesters can be built on them. They can be turned into large or huge barren planets with a factory ship.
Planet gaia.png
Gaia biome with unique colony ship landing animation, always huge and the single planet of its system. Protected by the Guardian, which must be defeated prior to colonization.