Planet Classes

Starfleet divides planets into several classes. These provide a shorthand guide for what sorts of life, in any, the planet is suitable for, as well as a general idea of its size and any hazards it poses. There are many subclasses that provide greater precision and detail, necessary given that a wide range of worlds can fit into a single class.

Class D

Class D planets are entirely lifeless and airless, and come in a variety of sizes. They may be suitable for terraforming given sufficient time.

Class J

Class J planets are gas giants such as Jupiter and Saturn. While incompatible with humanoid life, some do have other types of atmospheric life.

Class H

Class H planets have environmental conditions that render them unsuitable for typical humanoid life, but may be compatible with other life forms. Benzar is a Class H world, as its atmosphere is poisonous to most humanoids while the gasses are necessary for Benzite respiration. The Sheliak prefer Class H worlds.

Class K

Class K planets have such thin atmospheres that humanoid life can't survive without artificial support, even if the temperature is otherwise suitable. Pre-terraforming Mars was a Class K world.

Class L

Class L planets are 'marginal' worlds that have primitive life-forms. Often they have vegetation but little or no animal life, not unlike many early stages of development on Earth, and conditions may make it difficult for more advanced life to flourish. Atmospheric conditions may make it difficult for humanoid life to thrive, such as low oxygen content.

Class M

Class M planets are terrestrial and temperate worlds that are easily inhabited by most humanoid life in at least some major regions. There is a thriving natural ecosphere. Sub-types of Class M indicate other conditions such as day-night cycle, average temperature and aridity, and gravity. While Earth is the classic example of a Class M world, it can encompass extremes such as Vulcan and Andoria.

Class N

Class N worlds are similar to Class M in size, but have extremely high temperatures and often very dense and high-pressure atmospheres. Venus is a Class N world due to its runaway greenhouse effect. Tholians thrive in Class N conditions

Class O

Class O worlds are pelagic in nature, with over 80% over the surface covered by water, but otherwise having a humanoid-compatible oxygen atmosphere. These worlds often have strong weather patterns to the effects of oceaning heating, cooling, and humidity.

Class P

Class P worlds are heavily or entirely glaciated, often to the extent that even the equatorials regions never go above freezing. Most humanoid life can't survive long without artificial means, even relatively cold-adapted species such as Andorians. Life may exist below the ice layer.

Class R

Class R worlds are frozen to the point that conventional life is unable to survive. Many smaller planetoids are Class R.