Back  •   Locations  •   Index Planetary Typology Terrestrial planets Class Size Temperature Core Mantle/ Crust Oceans Atmosphere Notes Hermean Microterrestrial-Subterrestrial Any Large Iron Si None Trace Selenian Dwarf-Subterrestrial Any Small Iron Si None Trace Callistan Dwarf-Subterrestrial Any Ice-Rock Si None Trace Arean Subterrestrial-Terrestrial Any Small Iron Si None Thin CO2 Evolved Europan Dwarf-Subterrestrial Very Cold Small Iron Si Subsurface H2O Trace Moderate tidal flexing Titanian Microterrestrial-Subterrestrial Very Cold Ice-Rock C Hydrocarbons N2 CH3, CH4 clouds Ionian Dwarf-Subterrestrial Any Small Iron Si None Trace Molten surface from massive tidal flexing Cytherian Subterrestrial- Megaterrestrial Very Hot Iron Si None Massive CO2 H2SO4clouds; Cataclysmic geology; Runaway Greenhouse Helosian Subplanetary- Megaterrestrial Very Hot Any Any None None Molten surface from solar proximity Atlasian Megaterrestrial Any Large Iron Any None Massive Molten surface from gravity Hadean Any Any Any Any None Thick CO2 Molten surface from bombardment Heraclesian Subterrestrial- Superterrestrial Very Hot Large Iron Si None Massive N2, NH3 Runaway Greenhouse Chthonian Xeric Superterrestrial-Megaterrestrial Cold to Hot Large Iron Si None Thick or Massive N2, CO2, He Failed gas giant Chthonian Oceanic Superterrestrial-Megaterrestrial Temperate Large Iron Si H2O N2, CO2, He Failed gas giant Athenian Xeric Subterrestrial- Superterrestrial Temperate to Very Hot Large Iron Fe None CO, CO2 Stripped Mantle Athenian Oceanic Subterrestrial- Superterrestrial Temperate Large Iron Fe Fe(CO)5 CO, CO2 Stripped Mantle Artemisan Xeric Superterrestrial-Megaterrestrial Temperate to Very Hot Large Iron Fe None CO, CO2, He Stripped Mantle Artemisian Oceanic Superterrestrial-Megaterrestrial Temperate Large Iron Fe FE(CO)5 CO, CO2, He Stripped Mantle Hephestian Xeric Subterrestrial- Superterrestrial Cold to Very Hot Large Iron C None N2, CH4, CO Hephestian Oceanic Subterrestrial- Superterrestrial Very Cold to Cold Large Iron C Hydrocarbons N2, CH4, CO Theoretical hydrocarbon-based biochemistry Apollonian Xeric Superterrestrial- Megaterrestrial Cold to Very Hot Large Iron C None N2, He, CH4, CO Apollonian Oceanic Superterrestrial Megaterrestrial Very Cold to Cold Large Iron C Hydrocarbons N2, He, CH4, CO Styxian Xeric Temperate to Hot Si None SO2, SO3, O2 Styxian Oceanic Temperate to Hot Si H2SO4 SO2, SO3, O2 Typhonic Xeric Cold to Temperate Si None SO2, N2 Typhonic Oceanic Cold to Temperate Si SO2 SO2, N2 Dionysian Xeric Temperate to Hot Si None N2, NO2 High UV Dionysian Oceanic Temperate to Hot Si HNO3 N2, NO2 High UV Persephonean Xeric Cold None Thin NH3, N2 Low UV Persephonean Oceanic Cold NH3, H2O Thin NH3, N2 Low UV Theoretical ammonia-based biochemistry Eosian Xeric Subterrestrial- Megaterrestrial Cold to Hot Large Iron Si None CO2, N2 Smaller Eosians must be young Eosian Oceanic Subterrestrial- Megaterrestrial Temperate Large Iron Si H2O CO2, N2 Water clouds Eosian Panthalassic Subterrestrial- Megaterrestrial Temperate Large Iron Si Massively deep H2O CO2, N2 Archean Xeric Subterrestrial- Megaterrestrial Cold to Hot Large Iron Si None CO2, N2, O2 Carbon-Water biochemistry Smaller Archeans must be young Archean Oceanic Subterrestrial- Megaterrestrial Temperate Large Iron Si H2O CO2, N2, O2 Terran Hestian Subterrestrial- Superterrestrial Temperate Large Iron Si H2O N2, O2, CO2 Oceanic; Simple Carbon-Water biochemistry Smaller Terrans must be young Terran Gaean Terrestrial- Superterrestrial Temperate Large Iron Si H2O N2, O2 Oceanic; Complex Carbon-Water biochemistry Terran Tithonian Subterrestrial- Superterrestrial Temperate Large Iron Si H2O N2, O2 Carbon-Water biochemistry Limited tectonics Oceans dissociating Terran Melpomenean Terrestrial- Superterrestrial Temperate Large Iron Si H2O N2, O2, Cl2 Oceanic; Carbon-Water-Chlorine biochemistry Terran Cryogenian Subterresrial- Superterrestrial Cold-Temperate Large Iron Si H2O N2, O2 Runaway Glaciation Carbon-Water biochemistry Oceanic worlds may be arid (mostly land), pontic (mix of oceans and landmasses), epeiric (mostly shallow seas), nesoic (mostly ocean with islands), or pelagic (entirely ocean). Dwarf planets are large enough to maintain hydrostatic equilibrium but are typically less than one percent Earth mass; microterrestrial are between 1 and 5 percent; subterrestrial between 5 and 50 percent; terrestrial between 50 and 200 percent; superterrestrial between 2 and 5 Earth masses, and megaterrestrial between 5 and 10 Earth masses. Jovian planets range between 10 Earth masses and 4,300 Earth masses. Bodies above 4,300 Earth masses (13.5 Jupiter masses) may fuse deuterium and are considered brown dwarfs. Gas Giants Psamathean (Sandy Jovian): Extremely hot with silicate and iron clouds; dark muddy brown to white and green Salacian (Alkali Jovian): Very hot with sodium and potassium clouds; dark muddy brown to dark gray Theian (Clarified Jovian): Warm to hot with no clouds; deep blue Acheronan (Sulfur Jovian): Temperate with sulfurous clouds; yellow and gold Tethysian (Ice Jovian): Cold to temperate with water clouds; blue and white Jovian (Ammonia Jovian): Very cold with ammonia clouds; gold, tan, brown, white Posidean (Methane Jovian): Extremely cold with methane clouds; cyan to blue

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