Planetary nomenclature

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contents adapted from the public domain work United States Geological Survey [Gazetteer of Planetary Nomenclature].


Planetary nomenclature, like terrestrial nomenclature, is used to uniquely identify a feature on the surface of a planet or satellite so that the feature can be easily located, described, and discussed.

How names are approved

When images are first obtained of the surface of a planet or satellite, a theme for naming features is chosen and a few important features are named, usually by members of the appropriate IAU task group. Later, as higher resolution images and maps become available, additional features are named at the request of investigators mapping or describing specific surfaces, features, or geologic formations. Anyone may suggest that a specific name be considered by a task group. If the members of the task group agree that the name is appropriate, it can be retained for use when there is a request from a member of the scientific community that a specific feature be named. Names successfully reviewed by a task group are submitted to the IAU Working Group for Planetary System Nomenclature (WGPSN). Upon successful review by the members of the WGPSN, names are considered provisionally approved and can be used on maps and in publications as long as the provisional status is clearly stated. Provisional names are then presented for adoption to the IAU's General Assembly, which meets triennially. A name is not considered to be official--that is, "adopted"--until the General Assembly has given its approval.

IAU Rules and Conventions

Names adopted by the IAU must follow various rules and conventions established and amended through the years by the Union. These include:

  1. Nomenclature is a tool and the first consideration should be to make it simple, clear, and unambiguous.
  2. The number of names chosen for each body should be kept to a minimum, and their placement governed by the requirements of the scientific community.
  3. Duplication of the same name on two or more bodies is to be avoided.
  4. Individual names chosen for each body should be expressed in the language of origin. Transliteration for various alphabets should be given, but there will be no translation from one language to another.
  5. Where possible, the themes established in early solar system nomenclature should be used and expanded on.
  6. Solar system nomenclature should be international in its choice of names. Recommendations submitted to the IAU national committees will be considered, but final selection of the names is the responsibility of the International Astronomical Union. The WGPSN strongly supports equitable selection of names from ethnic groups/countries on each map; however, a higher percentage of names from the country planning a landing is allowed on landing site maps.
  7. No names having political, military or religious significance may be used, except for names of political figures prior to the 19th century.
  8. Commemoration of persons on planetary bodies should not be a goal in itself but should be reserved for persons of high and enduring international standing. Persons being so honored must have been deceased for at least three years.
  9. When more than one spelling of a name is extant, the spelling preferred by the person, or used in an authoritative reference, should be used. Diacritical marks are a necessary part of a name and will be used.
  10. Ring and ring-gap nomenclature and names for newly discovered satellites are developed in joint deliberation between WGPSN and IAU Commission 20. Names will not be assigned to satellites until their orbital elements are reasonably well known or definite features have been identified on them.

In addition to these general rules, each task group develops additional conventions as it formulates an interesting and meaningful nomenclature for individual planetary bodies.

Naming Conventions

Names for all planetary features include a descriptor term, with the exception of two feature types. For craters, the descriptor term is implicit. Some features named on Io and Triton do not carry a descriptor term because they are ephemeral.

In general, the naming convention for a feature type remains the same regardless of its size. Exceptions to this rule are channels (valles) on Mars and craters on the Moon, Mars, and Venus; naming conventions for these features differ according to size. The categories for naming features on each planet or satellite (and the exceptions) are listed in Appendix 6. One feature classification, regio, was originally used on early maps of the Moon and Mercury (drawn from telescopic observations) to describe vague albedo features. It is now used to delineate a broad geographic region.

Named features on bodies so small that coordinates have not yet been determined are identified on drawings of the body that are included in the IAU Transactions volume of the year when the names were adopted. Satellite rings and gaps in the rings are named for scientists who have studied these features; drawings that show these names are also included in the pertinent Transactions volume. Names for atmospheric features are informal at present; a formal system will be chosen in the future.

The boundaries of many large features (such as terrae, regiones, planitiae, and plana) are not topographically or geomorphically distinct; the coordinates of these features are identified from an arbitrarily chosen center point. Boundaries (and thus coordinates) may be determined more accurately from geochemical and geophysical data obtained by future missions.

Descriptor Terms (Feature Types)

FEATURE                  DESCRIPTION                                 DESIG.

Albedo Feature                                                         AL
Astrum, astra            Radial-patterned features on Venus            AS
Catena, catenae          Chain of craters                              CA
Cavus, cavi              Hollows, irregular steep-sided depressions    CB
                         usually in arrays or clusters
Chaos                    Distinctive area of broken terrain            CH
Chasma, chasmata         A deep, elongated, steep-sided depression     CM
Colles                   Small hills or knobs                          CO
Corona, coronae          Ovoid-shaped feature                          CR
Crater, craters          A circular depression                         AA
Dorsum, dorsa            Ridge                                         DO
Eruptive center          Active volcanic centers on Io                 ER
Facula, faculae          Bright spot                                   FA
Farrum, farra            Pancake-like structure, or a row of such      FR
Flexus, flex\-us         A very low curvilinear ridge with a           FE
			 scalloped pattern
Fluctus, fluct\-us       Flow terrain                                  FL
Fossa, fossae            Long, narrow, shallow depression              FO
Labes, lab\-es           Landslide                                     LA
Labyrinthus, labyrinthi  Complex of intersecting valleys               LB
Lacus(1)                 "Lake"; small plain                           LC
Landing site name        Lunar features at or near Apollo landing      LF
Large ringed feature     Cryptic ringed features                       LG
Lenticula, lenticulae    Small dark spots on Europa                    LE
Linea, lineae            A dark or bright elongate marking, may be     LI
                         curved or straight
Macula, maculae          Dark spot, may be irregular                   MA
Mare(1), maria           "Sea"; large circular plain                   ME
Mensa, mensae            A flat-topped prominence with cliff-like      MN
Mons, montes             Mountain                                      MO
Oceanus(1)               A very large dark area on the moon            OC
Palus(1), paludes        "Swamp"; small plain                          PA
Patera, paterae          An irregular crater, or a complex one with    PE
                         scalloped edges
Planitia, planitiae      Low plain                                     PL
Planum, plana            Plateau or high plain                         PM
Plume                                                                  PU
Promontorium(1),         "Cape"; headland                              PR
Regio, regiones          A large area marked by reflectivity or        RE
                         color distinctions from adjacent areas, or
                         a broad geographic region
Reticulum, reticula      reticular (netlike) pattern on Venus          RT 
Rima, rimae(1)           Fissure                                       RI
Rupes, rup\-es           Scarp                                         RU
Scopulus, scopuli        Lobate or irregular scarp                     SC
Sinus                    "Bay"; small plain                            SI
Sulcus, sulci            Subparallel furrows and ridges                SU
Terra, terrae            Extensive land mass                           TA
Tessera, tesserae        Tile-like, polygonal terrain                  TE
Tholus, tholi            Small domical mountain or hill                TH
Undae                    Dunes                                         UN
Vallis, valles           Valley                                        VA
Vastitas, vastitates     Extensive plain                               VS
(1) Used only on the Moon

Categories for naming features on planets and satellites


Craters                          Famous deceased artists, musicians,  painters, authors
Montes                           Caloris, from Latin word for "hot" 
Planitiae                        Names for Mercury (either planet or god) in various languages
Rup\-es                          Ships of discovery or scientific expeditions 
Valles                           Radio telescope facilities


Astra                            Goddesses, miscellaneous
Chasmata                         Goddesses of hunt; moon goddesses
Colles                           Sea goddesses
Coronae                          Fertility and earth goddesses
Craters                          Over 20 km; famous women; under 20 km, common female first names
Dorsa                            Sky goddesses
Farrum                           Water goddesses
Fluct\-us                        Goddesses, miscellaneous
Fossae                           Goddesses of war
Labyrinthus                      Goddesses, miscellaneous
Lineae                           Goddesses of war
Montes                           Goddesses, miscellaneous (also one radar  scientist)
Paterae                          Famous women
Planitiae                        Mythological heroines
Planum                           Goddesses of prosperity
Regiones                         Giantesses and Titanesses (also two Greek alphanumeric)
Rup\-es                          Goddesses of hearth and home
Tesserae                         Goddesses of fate and fortune
Terrae                           Goddesses of love
Tholi                            Goddesses, miscellaneous                             
Undae                            Desert goddesses
Valles                           Word for planet Venus in various world languages (400 km and longer)

River goddesses (less than 400 km in length)


Craters, Catenae, Dorsa, Rimae   Large craters: famous deceased scientists, scholars,
                                artists; small craters: common first names.   Other features
                                 named from nearby craters
Lac\-us, Maria, Paludes, Sin\-us Latin terms describing weather and other  abstract concepts
Montes                           Terrestrial mountain ranges or nearby craters
Rup\-es                          Name of nearby mountain ranges (terrestrial names)
Valles                           Name of nearby features



Large craters                    Deceased scientists who have contributed to the study of
                                Mars; writers and others who have contributed to the lore of Mars
Small craters                    Villages of the world with a population of  less than 100,000. 
Large valles                     Name for Mars/star in various languages
Small valles                     Classical or modern names of rivers
Other features                   From nearest named albedo feature on Schiaparelli or
                                Antoniadi maps


Authors who wrote about martian satellites


Scientists involved with the discovery, dynamics, or properties of the martian satellites 



People and places associated with the Amalthea myth


People and places associated with the Thebe myth


Active eruptive centers          Fire, sun, thunder gods and heroes
Catenae                          Sun gods
Fluct\-us                        Name derived from nearby named feature, 

or fire, sun, thunder, volcano gods, goddesses and heroes, mythical blacksmiths

Mensae                           People associated with Io myth, derived from 

nearby feature, or from Dante's Inferno

Montes                           Places associated with Io myth, derived from 

nearby feature, or from Dante's Inferno

Paterae                          Fire, sun, thunder, volcano gods, heroes, goddesses,
                                mythical blacksmiths
Plana                            Places associated with Io myth, derived from 

nearby feature, or from Dante's Inferno

Regiones                         Places associated with Io myth, derived from 

nearby feature, or from Dante's Inferno

Tholi                            Places associated with Io myth, derived from 
                                nearby feature, or from Dante's Inferno


Chaos                            Places associated with Celtic myths
Craters                          Celtic gods and heroes
Flex\-us                         Places associated with the Europa myth
Large ringed features            Celtic stone circles
Lenticulae                       Celtic gods and heroes
Lineae                           People associated with the Europa myth
Maculae                          Places associated with the Europa myth
Regiones                         Places associated with Celtic myths


Catenae                          Gods and heroes of ancient Fertile Crescent people 
Craters                          Gods and heroes of ancient Fertile Crescent people
Faculae                          Places associated with Egyptian myths
Fossae                           Gods (or principals) of ancient Fertile Crescent people
Regiones                         Astronomers who discovered Jovian satellites
Sulci                            Places associated with myths of ancient people


Large ringed features            Homes of the gods and of heroes
Craters                          Heroes and heroines from northern myths
Catenae                          Mythological places in high latitudes



People from myth of Castor and Pollux (twins)


People from myth of Castor and Pollux (twins)


People and places from Malory's Le Morte Darthur legends (Baines translation)


People and places from Burton's Arabian Nights


People and places from Homer's Odyssey


People and places from Virgil's Aeneid


People and places from creation myths


Ancient displaced cultures


Sun and Moon deities


People and places from Sayers' translation of Chanson de Roland


People associated with Phoebe, islands of the Greek archipelagos



Mischievous (Pucklike) spirits (class)


Characters, places from Shakespeare's plays


Light spirits (individual and class)


Dark spirits (individual)


Female Shakespearean characters, places


Shakespearean tragic heroes and places


Heroines from Shakespeare and Pope



Water-related spirits, gods, goddesses (excluding Greek and
                                Roman names)


Aquatic names, excluding Roman and Greek.  Possible
                                categories include worldwide aquatic spirits, famous
                                terrestrial fountains or fountain locations, terrestrial
                                aquatic features, famous terrestrial geysers or geyser
                                locations, terrestrial islands.


Individual nereids


Gods and goddesses associated with Neptune/Poseidon
                                mythology or generic mythological aquatic beings


Underworld deities



Craters                          Caverns and grottos of the world
Dorsa                            Galileo project participants
Regiones                         Discoverer of Ida and places associated with the


Craters                          Idaean dactyls


Craters                          Spas of the world
Regiones                         Discoverer of Gaspra, and Galileo project participants


Craters                          Coal fields and basins of the world


Craters                          Mythological and legendary names of an erotic nature 
Regiones                         Discoverers of Eros 
Dorsa                            Scientists who have contributed to the exploration and study of Eros