Class K planet

In the Federation standard system of planetary classification, a class K (or K type) planet was characterized as being adaptable for Humans by use of pressure domes and life support systems. An example of a class K planet is Mudd. 

The transjovian subtype of this class is used for harsh planets such as Theta 116 VIII, with average surface temperatures well below 0 &deg;C and an atmosphere consisting of methane, nitrogen and liquid neon. 

Background
According to the non-canon publication Star Trek: Star Charts, Class K planets are called "adaptable". These planets have an age that ranges from four to ten billion years and a diameter that ranges from 5,000 to 10,000 kilometers. A Class K planet is found within the ecosphere of a star system. They are categorized by a barren surface with little or no surface water and a thin atmosphere comprised mainly of carbon dioxide. Lifeforms found on Class K planets are limited to single-celled organisms, although Class K planets can be adapted for humanoid life through the use of pressure domes. According to the criteria, Mars could be considered a Class K planet.

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