Class M

In the Federation standard system of planetary classification, a class M planet, moon, or planetoid was considered to be suitable for humanoid life. By the mid-24th century, thousands of class M planets had been charted by the Federation. These worlds were the first choice for colonization. Since the late 23rd century, the Federation has been terraforming lifeless worlds into class M worlds. Environmental conditions on Federation starships mimicked the class M environment. 
 * Atmosphere: The atmosphere contained large percentages of nitrogen and oxygen, and smaller percentages of trace elements. Most planets had nucleogenic particles in the atmosphere. (Atmospheres that lacked nucleogenic particles were incapable of producing rain.) The atmosphere on these worlds was approximately Earth normal.
 * Surface: The surface of these planets was abundant in water. Under the surface, there were additional sources of water. These worlds were geologically active. Minshara-class planets were sometimes associated with significant quantities of the colors blue and green visible (indicating water and plant life respectively).
 * Mantle: Some of these worlds had a bemonite mantle.
 * Planetary core: The planetary core of these planets was nickel-iron.
 * Life: These worlds had ecosystems and contained amino acids and protein readings. High percentages of both indicated healthy plant life. Many of these worlds supported carbon-based plant and animal life. (any non-carbon-based would have to be non-indigenous) A smaller number of these worlds had proto-humanoid, humanoid, and Proto-Vulcan humanoid lifeforms.
 * Other: Class M worlds emitted electromagnetic radiation. These worlds were rich in minerals.  The gravity on these worlds was generally Earth normal, but could be slightly less or slightly more.  Temperatures might potentially be hot, but there was an upper limit. They were rare in binary systems.  These planets were typically located in the habitable zones of their systems,  though terrestrial rogue planets could quantify as class M when sufficient heat from their interiors was vented outward by geological activities.

During the mid-22nd century, Vulcan science used the term Minshara-class for such planets. Vulcans were not able to determine if a planet was Minshara-class through orbital scans, instead sending down probes to collect the necessary data. In 2151, Starfleet officers were not familiar with the term and chose to adopt it. However, by 2154, Starfleet had adopted the term class M. A century later, that term was in general use in Starfleet, even though the term "Earth-type" was also occasionally used.

By the 23rd century, it was theorized that there was a mathematical probability of three million Earth-type planets in the Milky Way Galaxy alone. 

A planet could fall within the range of the M-class classification. This range was from 1 to 4. The Koinonian homeworld was an example of an M-class type 4 planet. 

Occasionally, the term was used to characterize an atmosphere rather than a planet. 

The standard environment aboard Federation starships was class M.

List of class M planets and moons

 * "Planet Hell"
 * 892-IV
 * Alpha Carinae II
 * Alpha Onias III
 * Altamid
 * Angel I
 * Ankari homeworld
 * Archer IV
 * Arret
 * Barradas III
 * Berengaria VII
 * Boraal II
 * Bringloid V
 * Ceti Alpha V
 * Delphi Ardu IV
 * Delta Theta III
 * (Vulcan system)
 * Dozaria
 * Draygo IV
 * Draylon II
 * Earth
 * Earth Two
 * Evora homeworld
 * Gamma Hromi II
 * Gamma Hydra IV
 * Haven
 * Hemikek IV
 * Koinonian homeworld
 * Kolarus III
 * Kylata II
 * Lactra VII
 * Lambda Paz
 * M-113
 * Makull's homeworld
 * Mariposa
 * Neural
 * Nibiru
 * Omicron Theta
 * Orellius
 * Organia
 * Orias III
 * Otrin's homeworld
 * Paxan homeworld
 * Pentarus II
 * Pentarus V
 * Pollux IV
 * Qo'noS
 * Quarra
 * Rakhar
 * Rakosa V
 * Rock Creature planet
 * Ruah IV
 * Rubicun III
 * Sarpeidon
 * Sigma Draconis III
 * Sigma Draconis IV
 * Sigma Draconis VI
 * Talos IV
 * Tarakis
 * Tarella
 * Tarok
 * Tarquin's planet
 * Terra 10
 * Terra Nova
 * Trialas IV
 * Unnamed moon of Mab-Bu VI
 * Unnamed moon in the same system as Allos' homeworld
 * Unnamed planet of the Minos Korva system
 * Unnamed planet in the Delta Quadrant
 * Unnamed sixth planet of System J-25
 * Vacca VI
 * Valakis
 * Valo I
 * Valo II
 * Valo III
 * Xahea
 * Xahea
 * Xahea

Background information

 * The term "class M" was first used in to describe the planet Talos IV. The variant "M class" was also often used. The term has become Star Trek shorthand for Earth-like, and due to obvious production practicalities is the "default" for planetary surface scenes.
 * The Vulcan term "Minshara-class" (first used in ) was used in Enterprise to denote planets that in other series would have been called class M by the writers, the implied consequence being that the two terms meant the same, and possibly even that M stood for Minshara. This assumption has been contested by some fans, but is at least supported by the reference book Star Trek: Star Charts. From an in-universe standpoint, the term M-class was first seen chronologically in a text within the Handbook of Exobiology in, the same episode that introduced Minshara-class. However, this mention was barely legible on-screen and may have been included by an art department not yet aware of the intention to use "Minshara class". The first spoken use of the word was in , in which Archer used it to describe Archer IV, a planet implied (but not confirmed) to be Minshara class in . The term continued to be used several more times in the final season, while "Minshara-class" made no more appearances. The last use of "Minshara class" was in season three's , where it was still used in 2156 in an alternate timeline. The term also appeared on Enterprise's computer displays, indicating that Starfleet adapted it eventually.
 * In, Spock called planet Arret class M despite the atmosphere having been ripped away, suggesting that the class M designation goes beyond being able to support life. Alternately, he could have been saying that the planet, prior to losing its atmosphere, would have been categorized as class M.
 * Ceti Alpha V was described as "barely Minshara class" in, but also as no more inhospitable and savage then the site of Australia's Botany Bay colony before colonization in , suggesting that even on a class M planet like Earth, there might be locations that stretch the definition.
 * According to Star Trek: Star Charts, class M planets have ages that range from 3 billion to 10 billion years and a diameter between 10,000 and 15,000 kilometers. They are located within the ecosphere of a star system.

Apocrypha
The novel Strangers from the Sky indicates that the term "class M" was used by Humans prior to First Contact with Vulcans, or indeed before Humanity reached any extra-solar planets.

External link


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