Planetary Classification

From Star Trek: Gamma One

Class	Description	Age (bil. yrs)	Diameter (1,000 kms)	Atmosphere	Solar System Zone	Life-Forms
Class A	Geothermally Active	0 to 2	1 to 10	Hydrogen Compounds	Ecosphere
Class B	Geomorteus	0 to 10	1 to 10	Extremely Tenuous; Negligible	Hot
Class C	Geoinactive	2 to 10	1 to 10	Frozen	Cold
Class D	Rocky Moon/Asteroid	2 to 10	0.1 to 4	Negligible	Ecosphere
Class E	Geoplastic	0 to 2	10 to 15	Hydrogen Compounds	Ecosphere	Carbon-Cycle
Class F	Geometallic	1 to 3	10 to 15	Hydrogen Compounds	Ecosphere	Silicon-Based
Class G	Geocrystalline	3 to 4	10 to 15	Carbon Dioxide	Ecosphere	Single-Cell Organisms
Class H	Desert	4 to 10	8 to 15	Heavy Gases, Metal Vapors	Ecosphere, Cold	Drought-Resistant
Class I	Gas Supergiant	2 to 10	140 to 1,000	Varying Zones	Ecosphere, Cold
Class J	Gas Giant	2 to 10	50 to 140	Varying Zones	Ecosphere, Cold	Hydrocarbon-Based
Class K	Adaptable	4 to 10	5 to 10	Carbon Dioxide	Ecosphere	Single-Cell Organisms
Class L	Marginal	4 to 10	10 to 15	Oxygen, Argon, Carbon Dioxide	Ecosphere	Plants
Class M	Terrestrial	3 to 10	10 to 15	Nitrogen, Oxygen, Argon, Carbon Dioxide	Ecosphere	Plants/Humanoid
Class N	Reducing	3 to 10	10 to 15	Carbon Dioxide, Sulfides	Hot
Class O	Pelagic	3 to 10	10 to 15	Nitrogen, Oxygen	Ecosphere, Cold	Water-Based, Aquatic vegetation, animal life, humanoids
Class P	Glaciated	3 to 10	10 to 15	Nitrogen, Oxygen	Cold	Hardy Plants/Animals
Class Q	Variable	2 to 10	4 to 15	Highly Variable	All	Highly Variable
Class R	Rogue	2 to 10	4 to 15	Negligible	Outside Solar System	Non-Photosynthetic
Class S	Small Ultragiant	2 to 10	10,000 to 50,000	Varying Zones	Cold
Class T	Large Ultragiant	2 to 10	50,000 to 120,000	Varying Zones	Cold
Class Y	"Demon"	2 to 10	10 to 15	Thermionic Radiation	All	Mimetic