Planet Classification: Difference between revisions

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{{Notice|This information largely comes from this [http://www.sttff.net/planetaryclass.html web site], which in turn based it upon sources from Star Trek.}}  Planets are classified according to their predominant properties.  While there is, at times, overlap in some of the classifications the primary classification of a planet assists travelers through space in identifying the primary characteristics of a planet more easily.
There are an incredible number of variations for different kinds of worlds which can be enchanted in space, this is an index of the general planet types and their average conditions.  Unless otherwise noted there can be variations which are outliers.


{{Planet Class
{{Planet Class
|class=A / Geothermal
|class=A / Geothermal
|type=Rock
|location=Any
|location=Any
|age=0-2 Billion Years
|radius=500 to 5,000 km
|atmosphere=Sulfer Dioxide / Carbon Dioxide
|atmosphere=Sulfer Dioxide / Carbon Dioxide
|surface=Rocky / Partially Molten
|surface=Rocky / Partially Molten
|composition=Igneous Silica / Basalt
|composition=Igneous Silica and Basalt
|habitability=None
|hab=None
}}
}}
These planets are generally young, rocky worlds that are rife with volcanic activity. This volcanic activity spews vast amounts of sulfur and carbon dioxide into the atmosphere, causing a greenhouse effect that keeps temperatures relatively hot. Such worlds have tenuous and toxic atmospheres and are unsuitable to any kind of life.
Class A planets are very small, barren worlds rife with volcanic activity. This activity traps carbon dioxide in the atmosphere and keeps temperatures on Class A planets very hot, no matter the location in a star system. When the volcanic activity ceases, the planet "dies" and is then considered a Class C planet. Examples include the planet Gothos.
 
When this extreme volcanic activity eventually ceases, the planet "dies" and becomes a Class C world.
 
Class A planets are common in the universe; Jupiter's moon Io is a prime example.


{{Planet Class
{{Planet Class
|class=B / Geomorteus
|class=B / Geomorteus
|type=Rock
|age=0-10 Billion Years
|location=Hot Zone
|location=Hot Zone
|radius=500 to 5,000 km
|atmosphere=Oxygen / Sodium / Hydrogen
|atmosphere=Oxygen / Sodium / Hydrogen
|surface=Barren / Molten in Places
|surface=Barren / Molten in Places
|composition=Iron / Potassium / Silicon
|composition=Iron, Potassium, Silicon
|habitability=None}}
|hab=None
 
}}
Class B planets are generally very small, very rocky worlds located within a star system's hot zone. In the harsh daylight, these planets are scorched by their parent star, often to the point of rock becoming molten. Because Class B worlds have little to no atmosphere, this heat quickly radiates away at night, leaving the dark side of the planet a frigid wasteland. As a result, these planets are highly unsuitable for humanoid life.
Class B planets are generally small worlds located within a star system's Hot Zone. Highly unsuited for humanoid life, Class B planets have thin atmospheres composed primarily of helium and sodium. The surface is molten and highly unstable; temperatures range from 450° in the daylight, to nearly -200° at night. No life forms have ever been observed on Class B planetoids, though they are fairly common in the universe. Despite their small size, Class B planets are often extremely dense, with a large inner core, up to 55% of the planet's volume, that is made of molten iron. Examples include Mercury and Nebhillium.
 
Despite their small size, Class B planets are often extremely dense, with a large inner core, up to 55% of the planet's volume, that is made of molten iron.
 
Class B planets are fairly common in the universe.


{{Planet Class
{{Planet Class
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|surface=Barren and Cratered
|surface=Barren and Cratered
|composition=Anthracite and Basalt
|composition=Anthracite and Basalt
|habitability=None}}
|hab=None
|type=Rock
|age=2-10 Billion Years
|radius=500 to 5,000 km
}}
When all volcanic activity on a Class A planet ceases, it is considered Class C. Essentially dead, these small worlds have cold, barren surfaces and possess no geological activity.  These worlds are rocky and barren worlds which can exist in any zone of a star system, their surface temperature largely depends on the zone which they reside, generally speaking it runs between -150 to -120 degree's Celsius since most are located far enough away from the central star to absorb enough heat to bake the surface.  However, it is possible for these planets to be close enough to the central star to have surface temperatures much higher, though generally below that of a Class B world.  They tend to run smaller than a Class M world, with sizes ranging from that of moons up to just a bit smaller than an M Class world.  The primary classification of this class is the lack of an atmosphere, no geological activity, and the lack of any ability to support life.


These worlds are rocky and barren worlds which can exist in any zone of a star system, their surface temperature largely depends on the zone which they reside, generally speaking it runs between -150 to -120 degree's Celsius since most are located far enough away from the central star to absorb enough heat to bake the surface.  However, it is possible for these planets to be close enough to the central star to have surface temperatures much higher, though generally below that of a Class B world.  They tend to run smaller than a Class M world, with sizes ranging from that of moons up to just a bit smaller than an M Class world.  The primary classification of this class is the lack of an atmosphere, no geological activity, and the lack of any ability to support life.
These worlds are often rich in minerals and make incredibly good candidates for mining operations.  Some can even have semi-molten iron cores with rich deposits of minerals produced either by steady impact of meteorites during the early phases of their existence (usually these worlds begin as Class A worlds or similar and then become more inactive as they cool over several billion years).  Examples include Psi 2000.
 
These worlds are often rich in minerals and make incredibly good candidates for mining operations.  Some can even have semi-molten iron cores with rich deposits of minerals produced either by steady impact of meteorites during the early phases of their existence (usually these worlds begin as Class A worlds or similar and then become more inactive as they cool over several billion years).


{{Planet Class
{{Planet Class
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|surface=Barren / Cratered
|surface=Barren / Cratered
|atmosphere=None / Very Tenuous
|atmosphere=None / Very Tenuous
|habitability=None
|hab=None
|type=Rock
|age=2-10 Billion Years
|radius=50 to 2,000 km
|composition=Frozen Hydrocarbons and Ice
}}
}}
Also known as Plutonian objects, these tiny worlds are composed primarily of ice and are generally not considered true planets. Many moons and asteroids are considered Class D, as are the larger objects in a star system's Kuiper Belt. Most are not suitable for humanoid life, though many can be colonized via pressure domes.  Examples include Pluto, Ceres, and Eredas-II.


Also known as Plutonian objects, these tiny worlds (100 - 4,000 km) are composed primarily of ice and are generally not considered true planets. Many moons and asteroids are considered Class D, as are the larger objects in a star system's Kuiper Belt. Most are not suitable for humanoid life, though many can be colonized via pressure domes.  Examples include Pluto, Ceres, and Eredas-II.
{{Planet Class
|class=E / Geoplastic
|type=Rock
|age=2-10 Billion Years
|radius=5,000 to 7500 km
|location=Ecosphere
|surface=Molten with High Surface Temperature
|atmosphere=Hydrogen Compounds
|hab=Carbon Cycle Life
|composition=Silicone, Iron, Magnesium, Aluminum
}}
Class E planets represent the earliest stage in the evolution of a habitable planet. The core and crust is completely molten, making the planets susceptible to solar winds and radiation and subject to extremely high surface temperatures. The atmosphere is very thin, composed of hydrogen and helium. As the surface cools, the core and crust begin to harden, and the planet evolves into a Class F world.
 
{{Planet Class
|class=F / Geometallic
|type=Rock
|age=1-3 Billion Years
|radius=5,000 to 7500 km
|location=Ecosphere
|surface=Volcanic and Barren
|atmosphere=Carbon Dioxide, Ammonia, Methane
|composition=Silicone, Iron, Magnesium, Aluminum
|hab=Bacteria
}}
A Class E planet makes the transition to Class F once the crust and core have begun to harden. Volcanic activity is also commonplace on Class F worlds; the steam expelled from volcanic eruptions eventually condenses into water, giving rise to shallow seas in which simple bacteria thrive. When the planet's core is sufficiently cool, the volcanic activity ceases and the planet is considered Class G. Examples include Janus IV.
 
{{Planet Class
|class=G / Geocrystalline
|type=Rock
|age=3-4 Billion Years
|radius=5,000 to 7500 km
|location=Ecosphere
|surface=Rocky and Mostly Barren
|atmosphere=Carbon Dioxide, Oxygen, Nitrogen
|hab=Vegetation / Simple Organisms
|composition=Silicone, Iron, Magnesium, Aluminum
}}
After the core of a Class F planet is sufficiently cool, volcanic activity lessens and the planet is considered Class G. Oxygen and nitrogen are present in some abundance in the atmosphere, giving rise to increasingly complex organisms such as primitive vegetation like algae, and animals similar to sponges and jellyfish. As the surface cools, a Class G planet can evolve into a Class H, K, L, M, N, O, or P class world.  Examples include Delta Vega.


{{Planet Class
{{Planet Class
|class=H / Desert
|class=H / Desert
|type=Rock
|age=4-10 Billion Years
|radius=5,000 to 7500 km
|location=Ecosphere
|location=Ecosphere
|surface=Hot / Arid with < 20% Surface Water
|surface=Hot / Arid with < 20% Surface Water
|atmosphere=Oxygen, Nitrogen, Argon, and Metals
|atmosphere=Oxygen, Nitrogen, Argon, and Metals
|habitability=Drought-Resistant Plants & Animals
|hab=Drought-Resistant Plants & Animals
|composition=Silicone, Iron, Magnesium, Aluminum
}}
}}
A planet is considered Class H if less than 20% of its surface is water. Though many Class H worlds are covered in sand, it is not required to be considered a desert; it must, however, receive little in the way of precipitation. These worlds are usually between 8,000 and 15,000 km in diameter.  Drought-resistant plants and animals are common on Class H worlds, and many are inhabited by humanoid populations. Most Class H worlds are hot and arid, but conditions can vary greatly.  Examples include Nimbus III and Ocampa.
A planet is considered Class H if less than 20% of its surface is water. Though many Class H worlds are covered in sand, it is not required to be considered a desert; it must, however, receive little in the way of precipitation. These worlds are usually between 8,000 and 15,000 km in diameter.  Drought-resistant plants and animals are common on Class H worlds, and many are inhabited by humanoid populations. Most Class H worlds are hot and arid, but conditions can vary greatly.  Examples include Nimbus III and Ocampa.
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{{Planet Class
{{Planet Class
|class=I / Ice Giant / Uranian
|class=I / Ice Giant / Uranian
|type=Gas Giant
|age=2-10 Billion Years
|location=Cold Zone
|location=Cold Zone
|atmosphere=Hydrogen , Helium
|radius=15,000 to 50,000 km
|surface=Rock, Ice, Methane, Ammonia
|atmosphere=Hydrogen and Helium
|surface=Rock, Ice, Methane, and Ammonia
|composition=Hydrogen, Helium
|composition=Hydrogen, Helium
|habitability=None}}
|hab=None
 
}}
These planets are gas giants with a core of mostly rock surrounded by tenuous layers of methane, water, and ammonia. They have a sharply inclined magnetic field compared to the axis of rotation. They typically form on the fringe of a solar system.  They can be excellent sources of Hydrogen and Helium, smaller than a Class J and with a weaker magnetic and gravitational field making extracting Hydrogen easier than a Class J.  These are similar to Neptune and Uranus in the Sol System.
Also known as Uranian planets, these gaseous giants have vastly different compositions from other giant worlds; the core is mostly rock and ice surrounded by a tenuous layers of methane, water, and ammonia. Additionally, the magnetic field is sharply inclined to the axis of rotation. Class I planets typically form on the fringe of a star system.


{{Planet Class
{{Planet Class
|class=J / Gas Giant / Jovian
|type=Gas Giant
|radius=25,000 to 250,000 km
|class=J / Jovian
|location=Cold Zone
|location=Cold Zone
|atmosphere=Hydrogen , Helium
|atmosphere=Hydrogen , Helium
|surface=Liquid Metallic Hydrogen
|surface=Liquid Metallic Hydrogen
|composition=Hydrogen, Helium
|composition=Hydrogen, Helium
|habitability=None}}
|hab=None
 
}}
These planets are massive spheres of liquid and gaseous hydrogen, with small cores of metallic hydrogen similar to Jupiter in the Sol system. Their atmospheres are extremely turbulent, with wind speeds in the most severe storms reaching 600 kph. Many Class J planets also possess impressive ring systems, composed primarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I planets.  The strong magnetic and gravitational fields can pose a navigational hazard to nearby vessels and also can make extraction of Hydrogen more difficult than Class I worlds.
These are prototypical gas giants, class J planets are massive spheres of liquid and gaseous hydrogen, with small cores of metallic hydrogen. Their atmospheres are extremely turbulent, with wind speeds in the most severe storms reaching 600 kph. Many Class J planets also possess impressive ring systems, composed primarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I planets. Their atmospheres are extremely turbulent, with wind speeds in the most severe storms reaching 600 kph. Many Class J planets also possess impressive ring systems composed primarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I planets.  The strong magnetic and gravitational fields can pose a navigational hazard to nearby vessels and also can make extraction of Hydrogen more difficult than Class I worlds.


{{Planet Class
{{Planet Class
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|surface=Barren and Cratered
|surface=Barren and Cratered
|composition=Silicone, Iron, Magnesium, Aluminum
|composition=Silicone, Iron, Magnesium, Aluminum
|habitability=Adaptable}}
|hab=Adaptable
|radius=2,500 to 5,000 km
|type=Rock
|age=4-10 Billion Years
}}
Though similar in appearance to Class H worlds, Class K planets lack the robust atmosphere of their desert counterparts. Though rare, primitive single-celled organisms have been known to exist, though more complex life never evolves. Humanoid colonization is, however, possible through the use of pressure domes and in some cases, terraforming.  Adaptable planets represent an unfortunate part of planetary development: a failed world. Over the course of a terrestrial planet's long and arduous evolution (from Class E to F to G), something, somewhere goes wrong, and the blossoming young planet fails to reach its full potential. Volcanic activity slows to a halt, the tenuous atmosphere begins to disperse, any liquid on the surface evaporates, and the rocky young world essentially dies.  These worlds have atmospheres of dwindling size after volcanic activity slows and the molten core begins to solidify.  Examples include Mars and Mudd.


Adaptable planets represent an unfortunate part of planetary development: a failed world. Over the course of a terrestrial planet's long and arduous evolution (from Class E to Class F to Class G), something, somewhere goes wrong, and the
Though rare, simple single cell organisms can still thrive on these barren worlds more complex forms of life never evolve. As a result, Class K planets are easily colonized via the use of pressure domes, and are often prime candidates for terraforming. Average temperatures are quite cold by humanoid standards, but a warm summer day on a terraformed Class K planet might creep as high as 20°C.
blossoming young planet fails to reach its full potential. Volcanic activity slows to a halt, the tenuous atmosphere begins to disperse, any liquid on the surface evaporates, and the rocky young world essentially dies.  These worlds have atmospheres of dwindling size after volcanic activity slows and the molten core begins to solidify.
 
Though rare, simple single cell organisms can still thrive on these barren worlds, but more complex forms of life never evolve. As a result, Class K planets are easily colonized via the use of pressure domes, and are often prime candidates for terraforming. Average temperatures are quite cold by humanoid standards, but a warm summer day on a terraformed Class K planet might creep as high as 20°C.


{{Planet Class
{{Planet Class
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|surface=Rocky with Little Surface Water
|surface=Rocky with Little Surface Water
|atmosphere=Argon & Oxygen with Trace Elements
|atmosphere=Argon & Oxygen with Trace Elements
|habitability=Vegetation Only
|hab=Vegetation Only
|type=Rock
|radius=5,000 to 7,500 km
|age=4-10 Billion Years
|composition=Silicone, Iron, Magnesium, Aluminum
}}
}}
These planets are usually between 10,000 and 15,000 km in diameter, typically rocky, forested worlds devoid of animal life. They are, however, well-suited for humanoid colonization and are prime candidates for terraforming. Water is typically scarce, and if less than 20% of the surface is covered in water, the planet is considered Class H.  Examples include Alarin III, Ciden II, and Indri VII.
Typically rocky, forested worlds devoid of animal life. They are, however, well-suited for humanoid colonization and are prime candidates for terraforming. Water is typically scarce, and if less than 20% of the surface is covered in water, the planet is considered Class H.  Examples include Alarin III, Ciden II, and Indri VII.


{{Planet Class
{{Planet Class
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|surface=Abundant Surface Water, Temperate Climate
|surface=Abundant Surface Water, Temperate Climate
|composition=Silicone, Iron, Magnesium, Aluminium
|composition=Silicone, Iron, Magnesium, Aluminium
|habitability=Prime conditions for large populations of animal, planet, and humanoid life.}}
|hab=Prime conditions for large populations of animal, planet, and humanoid life.
|radius=5,000 to 7,500 km
|age=4-10 Billion Years
|type=Rock
}}
These planets are robust and varied worlds composed primarily of silicate rocks. Located in a star system's habitable zone, most are temperate worlds with vast blue oceans and wide swaths of verdant forest. However, conditions can vary greatly between worlds and still be considered Class M; as long as the surface is between 20 and 80 percent water, the climate is generally temperate, and the atmosphere made of oxygen and nitrogen, even dry rocky worlds or cold snowy planets can be Class M.


These planets are robust and varied worlds composed primarily of silicate rocks. Located in a star system's habitable zone, most are temperate worlds with vast blue oceans and wide swaths of verdant forest. However, conditions can vary greatly between worlds and still be considered Class M; as long as the surface is between 20 and 80 percent water, the climate is generally temperate, and the atmosphere made of oxygen and nitrogen, even dry rocky worlds and cold snowy planets can be Class M.
{{Planet Class
|class=N / Reducing
|radius=5,000 to 7,500 km
|location=Ecosphere
|surface=Barren with High Surface Temperatures
|composition=Silicone, Iron, Magnesium, Aluminium
|atmosphere=Carbon Dioxide and Sulfides
|age=3-10 Billion Years
|hab=None
|type=Rock
}}
Though frequently found in the Ecosphere, Class N planets are not conducive to life. The terrain is barren, with surface temperatures in excess of 500° and an atmospheric pressure more than 90 times that of a Class-M world. Additionally, the atmosphere is very dense and composed of carbon dioxide; water exists only in the form of thick, vaporous clouds that shroud most of the planet.  Examples include Venus.


{{Planet Class
{{Planet Class
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|surface=80% Water & Archipelagos
|surface=80% Water & Archipelagos
|composition=Silicone, Iron, Magnesium, Aluminium
|composition=Silicone, Iron, Magnesium, Aluminium
|habitability=Dense vegetation on land and large aquatic populations of flora and fauna.
|hab=Vegetation, Cetacean, Animal, Humanoid
|radius=5,000 to 7,500 km
|type=Rock
|age=3-10 Billion Years
}}
}}
Any planet with more than 80% of the surface covered in water is considered Class O. These worlds are usually very warm and possess vast cetacean populations in addition to tropical vegetation and animal life. Though rare, humanoid populations have also formed on Class O planets.
Any planet with more than 80% of the surface covered in water is considered Class O. These worlds are usually very warm and possess vast cetacean populations in addition to tropical vegetation and animal life. Though rare, humanoid populations have also formed on Class O planets.
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|surface=Cold, Glaciated
|surface=Cold, Glaciated
|composition=Silicon, Iron, Magnesium, Ice
|composition=Silicon, Iron, Magnesium, Ice
|habitability=Hearty flora and fauna capable of withstanding extreme cold.
|hab=Cold-Resistant Vegetation, Animal, and Humanoid
|age=3-10 Billion Years
|radius=5,000 to 7,500 km
|type=Rock
}}
}}
On the distant edge of a star system's ecosphere, habitable planets are still numerous, but they are a far cry from the lush garden worlds closer in. Cold, barren, and glaciated planet is covered in solid ice, and while many possess narrow stripes of green along the equator, where hearty plant and animal life may flourish, many glaciated worlds are entirely frozen.
On the distant edge of a star system's ecosphere, habitable planets are still numerous, but they are a far cry from the lush garden worlds closer in. Cold, barren, and glaciated planet is covered in solid ice, and while many possess narrow stripes of green along the equator, where hearty plant and animal life may flourish, many glaciated worlds are entirely frozen.


Revision as of 17:11, 25 December 2021

There are an incredible number of variations for different kinds of worlds which can be enchanted in space, this is an index of the general planet types and their average conditions. Unless otherwise noted there can be variations which are outliers.

A / Geothermal

Type: Rock
Age: 0-2 Billion Years
Atmosphere: Sulfer Dioxide / Carbon Dioxide
Radius: 500 to 5,000 km
Surface: Rocky / Partially Molten
Composition: Igneous Silica and Basalt
Location: Any
Habitability: None

Class A planets are very small, barren worlds rife with volcanic activity. This activity traps carbon dioxide in the atmosphere and keeps temperatures on Class A planets very hot, no matter the location in a star system. When the volcanic activity ceases, the planet "dies" and is then considered a Class C planet. Examples include the planet Gothos.

B / Geomorteus

Type: Rock
Age: 0-10 Billion Years
Atmosphere: Oxygen / Sodium / Hydrogen
Radius: 500 to 5,000 km
Surface: Barren / Molten in Places
Composition: Iron, Potassium, Silicon
Location: Hot Zone
Habitability: None

Class B planets are generally small worlds located within a star system's Hot Zone. Highly unsuited for humanoid life, Class B planets have thin atmospheres composed primarily of helium and sodium. The surface is molten and highly unstable; temperatures range from 450° in the daylight, to nearly -200° at night. No life forms have ever been observed on Class B planetoids, though they are fairly common in the universe. Despite their small size, Class B planets are often extremely dense, with a large inner core, up to 55% of the planet's volume, that is made of molten iron. Examples include Mercury and Nebhillium.

C / Geoinactive

Type: Rock
Age: 2-10 Billion Years
Atmosphere: None
Radius: 500 to 5,000 km
Surface: Barren and Cratered
Composition: Anthracite and Basalt
Location: Hot Zone / Echosphere / Cold Zone
Habitability: None

When all volcanic activity on a Class A planet ceases, it is considered Class C. Essentially dead, these small worlds have cold, barren surfaces and possess no geological activity. These worlds are rocky and barren worlds which can exist in any zone of a star system, their surface temperature largely depends on the zone which they reside, generally speaking it runs between -150 to -120 degree's Celsius since most are located far enough away from the central star to absorb enough heat to bake the surface. However, it is possible for these planets to be close enough to the central star to have surface temperatures much higher, though generally below that of a Class B world. They tend to run smaller than a Class M world, with sizes ranging from that of moons up to just a bit smaller than an M Class world. The primary classification of this class is the lack of an atmosphere, no geological activity, and the lack of any ability to support life.

These worlds are often rich in minerals and make incredibly good candidates for mining operations. Some can even have semi-molten iron cores with rich deposits of minerals produced either by steady impact of meteorites during the early phases of their existence (usually these worlds begin as Class A worlds or similar and then become more inactive as they cool over several billion years). Examples include Psi 2000.

D / Dwarf

Type: Rock
Age: 2-10 Billion Years
Atmosphere: None / Very Tenuous
Radius: 50 to 2,000 km
Surface: Barren / Cratered
Composition: Frozen Hydrocarbons and Ice
Location: Any
Habitability: None

Also known as Plutonian objects, these tiny worlds are composed primarily of ice and are generally not considered true planets. Many moons and asteroids are considered Class D, as are the larger objects in a star system's Kuiper Belt. Most are not suitable for humanoid life, though many can be colonized via pressure domes. Examples include Pluto, Ceres, and Eredas-II.

E / Geoplastic

Type: Rock
Age: 2-10 Billion Years
Atmosphere: Hydrogen Compounds
Radius: 5,000 to 7500 km
Surface: Molten with High Surface Temperature
Composition: Silicone, Iron, Magnesium, Aluminum
Location: Ecosphere
Habitability: Carbon Cycle Life

Class E planets represent the earliest stage in the evolution of a habitable planet. The core and crust is completely molten, making the planets susceptible to solar winds and radiation and subject to extremely high surface temperatures. The atmosphere is very thin, composed of hydrogen and helium. As the surface cools, the core and crust begin to harden, and the planet evolves into a Class F world.

F / Geometallic

Type: Rock
Age: 1-3 Billion Years
Atmosphere: Carbon Dioxide, Ammonia, Methane
Radius: 5,000 to 7500 km
Surface: Volcanic and Barren
Composition: Silicone, Iron, Magnesium, Aluminum
Location: Ecosphere
Habitability: Bacteria

A Class E planet makes the transition to Class F once the crust and core have begun to harden. Volcanic activity is also commonplace on Class F worlds; the steam expelled from volcanic eruptions eventually condenses into water, giving rise to shallow seas in which simple bacteria thrive. When the planet's core is sufficiently cool, the volcanic activity ceases and the planet is considered Class G. Examples include Janus IV.

G / Geocrystalline

Type: Rock
Age: 3-4 Billion Years
Atmosphere: Carbon Dioxide, Oxygen, Nitrogen
Radius: 5,000 to 7500 km
Surface: Rocky and Mostly Barren
Composition: Silicone, Iron, Magnesium, Aluminum
Location: Ecosphere
Habitability: Vegetation / Simple Organisms

After the core of a Class F planet is sufficiently cool, volcanic activity lessens and the planet is considered Class G. Oxygen and nitrogen are present in some abundance in the atmosphere, giving rise to increasingly complex organisms such as primitive vegetation like algae, and animals similar to sponges and jellyfish. As the surface cools, a Class G planet can evolve into a Class H, K, L, M, N, O, or P class world. Examples include Delta Vega.

H / Desert

Type: Rock
Age: 4-10 Billion Years
Atmosphere: Oxygen, Nitrogen, Argon, and Metals
Radius: 5,000 to 7500 km
Surface: Hot / Arid with < 20% Surface Water
Composition: Silicone, Iron, Magnesium, Aluminum
Location: Ecosphere
Habitability: Drought-Resistant Plants & Animals

A planet is considered Class H if less than 20% of its surface is water. Though many Class H worlds are covered in sand, it is not required to be considered a desert; it must, however, receive little in the way of precipitation. These worlds are usually between 8,000 and 15,000 km in diameter. Drought-resistant plants and animals are common on Class H worlds, and many are inhabited by humanoid populations. Most Class H worlds are hot and arid, but conditions can vary greatly. Examples include Nimbus III and Ocampa.

I / Ice Giant / Uranian

Type: Gas Giant
Age: 2-10 Billion Years
Atmosphere: Hydrogen and Helium
Radius: 15,000 to 50,000 km
Surface: Rock, Ice, Methane, and Ammonia
Composition: Hydrogen, Helium
Location: Cold Zone
Habitability: None

Also known as Uranian planets, these gaseous giants have vastly different compositions from other giant worlds; the core is mostly rock and ice surrounded by a tenuous layers of methane, water, and ammonia. Additionally, the magnetic field is sharply inclined to the axis of rotation. Class I planets typically form on the fringe of a star system.

J / Jovian

Type: Gas Giant
Age: Unknown
Atmosphere: Hydrogen , Helium
Radius: 25,000 to 250,000 km
Surface: Liquid Metallic Hydrogen
Composition: Hydrogen, Helium
Location: Cold Zone
Habitability: None

These are prototypical gas giants, class J planets are massive spheres of liquid and gaseous hydrogen, with small cores of metallic hydrogen. Their atmospheres are extremely turbulent, with wind speeds in the most severe storms reaching 600 kph. Many Class J planets also possess impressive ring systems, composed primarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I planets. Their atmospheres are extremely turbulent, with wind speeds in the most severe storms reaching 600 kph. Many Class J planets also possess impressive ring systems composed primarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I planets. The strong magnetic and gravitational fields can pose a navigational hazard to nearby vessels and also can make extraction of Hydrogen more difficult than Class I worlds.

K / Adaptable

Type: Rock
Age: 4-10 Billion Years
Atmosphere: Oxygen, Nitrogen, Argon
Radius: 2,500 to 5,000 km
Surface: Barren and Cratered
Composition: Silicone, Iron, Magnesium, Aluminum
Location: Echosphere
Habitability: Adaptable

Though similar in appearance to Class H worlds, Class K planets lack the robust atmosphere of their desert counterparts. Though rare, primitive single-celled organisms have been known to exist, though more complex life never evolves. Humanoid colonization is, however, possible through the use of pressure domes and in some cases, terraforming. Adaptable planets represent an unfortunate part of planetary development: a failed world. Over the course of a terrestrial planet's long and arduous evolution (from Class E to F to G), something, somewhere goes wrong, and the blossoming young planet fails to reach its full potential. Volcanic activity slows to a halt, the tenuous atmosphere begins to disperse, any liquid on the surface evaporates, and the rocky young world essentially dies. These worlds have atmospheres of dwindling size after volcanic activity slows and the molten core begins to solidify. Examples include Mars and Mudd.

Though rare, simple single cell organisms can still thrive on these barren worlds more complex forms of life never evolve. As a result, Class K planets are easily colonized via the use of pressure domes, and are often prime candidates for terraforming. Average temperatures are quite cold by humanoid standards, but a warm summer day on a terraformed Class K planet might creep as high as 20°C.

L / Marginal

Type: Rock
Age: 4-10 Billion Years
Atmosphere: Argon & Oxygen with Trace Elements
Radius: 5,000 to 7,500 km
Surface: Rocky with Little Surface Water
Composition: Silicone, Iron, Magnesium, Aluminum
Location: Ecosphere
Habitability: Vegetation Only

Typically rocky, forested worlds devoid of animal life. They are, however, well-suited for humanoid colonization and are prime candidates for terraforming. Water is typically scarce, and if less than 20% of the surface is covered in water, the planet is considered Class H. Examples include Alarin III, Ciden II, and Indri VII.

M / Minshara / Terrestrial

Type: Rock
Age: 4-10 Billion Years
Atmosphere: Oxygen, Nitrogen, Argon
Radius: 5,000 to 7,500 km
Surface: Abundant Surface Water, Temperate Climate
Composition: Silicone, Iron, Magnesium, Aluminium
Location: Ecosphere
Habitability: Prime conditions for large populations of animal, planet, and humanoid life.

These planets are robust and varied worlds composed primarily of silicate rocks. Located in a star system's habitable zone, most are temperate worlds with vast blue oceans and wide swaths of verdant forest. However, conditions can vary greatly between worlds and still be considered Class M; as long as the surface is between 20 and 80 percent water, the climate is generally temperate, and the atmosphere made of oxygen and nitrogen, even dry rocky worlds or cold snowy planets can be Class M.

N / Reducing

Type: Rock
Age: 3-10 Billion Years
Atmosphere: Carbon Dioxide and Sulfides
Radius: 5,000 to 7,500 km
Surface: Barren with High Surface Temperatures
Composition: Silicone, Iron, Magnesium, Aluminium
Location: Ecosphere
Habitability: None

Though frequently found in the Ecosphere, Class N planets are not conducive to life. The terrain is barren, with surface temperatures in excess of 500° and an atmospheric pressure more than 90 times that of a Class-M world. Additionally, the atmosphere is very dense and composed of carbon dioxide; water exists only in the form of thick, vaporous clouds that shroud most of the planet. Examples include Venus.

O / Oceanic / Pelagic

Type: Rock
Age: 3-10 Billion Years
Atmosphere: Oxygen, Nitrogen, Argon
Radius: 5,000 to 7,500 km
Surface: 80% Water & Archipelagos
Composition: Silicone, Iron, Magnesium, Aluminium
Location: Ecosphere
Habitability: Vegetation, Cetacean, Animal, Humanoid

Any planet with more than 80% of the surface covered in water is considered Class O. These worlds are usually very warm and possess vast cetacean populations in addition to tropical vegetation and animal life. Though rare, humanoid populations have also formed on Class O planets.

P / Glaciated

Type: Rock
Age: 3-10 Billion Years
Atmosphere: Oxygen, Nitrogen, Argon
Radius: 5,000 to 7,500 km
Surface: Cold, Glaciated
Composition: Silicon, Iron, Magnesium, Ice
Location: Ecosphere, Cold Zone
Habitability: Cold-Resistant Vegetation, Animal, and Humanoid

On the distant edge of a star system's ecosphere, habitable planets are still numerous, but they are a far cry from the lush garden worlds closer in. Cold, barren, and glaciated planet is covered in solid ice, and while many possess narrow stripes of green along the equator, where hearty plant and animal life may flourish, many glaciated worlds are entirely frozen.

Despite the harsh conditions, humanoid life can thrive on a glaciated world.

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