Planetary nomenclature, like terrestrial nomenclature, is a system of uniquely identifying features on the surface of a planet or natural satellite so that the features can be easily located, described, and discussed. Since the invention of the telescope, astronomers have given names to the surface features they have discerned, especially on the Moon and Mars. To found an authority on planetary nomenclature, the International Astronomical Union (IAU) was organized in 1919 to designate and standardize names for features on Solar System bodies.[1]
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 (a commonly accepted planet-naming 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 for a name of a specific feature. Names that pass review by a task group are submitted to the IAU Working Group for Planetary System Nomenclature (WGPSN). Once approved by the WGPSN, names are considered official and can be used on maps and in publications. They are also listed in the Gazetteer of Planetary Nomenclature.[2]
Names adopted by the IAU must follow various rules and conventions established and amended through the years by the Union. These include:
In addition to these general rules, each task group develops additional conventions as it formulates an interesting and meaningful nomenclature for individual planetary bodies.
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 valleys and craters on Mars and Venus; naming conventions for these features differ according to size.
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.
During active missions, small surface features are often given informal names. These may include landing sites, spacecraft impact sites, and small topographic features, such as craters, hills, and rocks. Such names will not be given official status by the IAU, except as provided for by Rule 2 above. As for the larger objects, official names for any such small features would have to conform to established IAU rules and categories.
| Feature | Pronunciation | Description | Designation | |
|---|---|---|---|---|
| Albedo feature | An area which shows a contrast in brightness or darkness (albedo) with adjacent areas. This term is implicit. | AL | ||
| Arcus, arcūs | Arc: curved feature | AR | ||
| Astrum, astra | , | Radial-patterned features on Venus | AS | |
| Catena, catenae | , | A chain of craters e.g. Enki Catena. | CA | |
| Cavus, cavi | , | Hollows, irregular steep-sided depressions usually in arrays or clusters | CB | |
| Chaos | A distinctive area of broken or jumbled terrain e.g. Iani Chaos. | CH | ||
| Chasma, chasmata | , | Deep, elongated, steep-sided depression e.g. Eos Chasma. | CM | |
| Collis, colles | , | A small hill or knob. | CO | |
| Corona, coronae | , | An oval feature. Used only on Venus and Miranda. | CR | |
| Crater, craters | A circular depression (in most cases created by impact event). This term is implicit. | AA | ||
| Dorsum, dorsa | , | Ridge, sometimes called a wrinkle ridge e.g. Dorsum Buckland. | DO | |
| Eruptive center | An active volcano on Io. This term is implicit. | ER | ||
| Facula, faculae | , | Bright spot | FA | |
| Farrum, farra | , | Pancake-like structure, or a row of such structures. Used only on Venus. | FR | |
| Flexus, flexūs | Very low curvilinear ridge with a scalloped pattern | FE | ||
| Fluctus, fluctūs | , | Terrain covered by outflow of liquid. Used on Venus, Io, Titan, and Mars. | FL | |
| Flumen, flumina | , | Channel on Titan that might carry liquid | FM | |
| Fossa, fossae | , | Long, narrow, shallow depression | FO | |
| Fretum, freta | , | Strait of liquid connecting two larger areas of liquid. Used only on Titan. | FT | |
| Insula, insulae | , | Island (islands), an isolated land area (or group of such areas) surrounded by, or nearly surrounded by, a liquid area (sea or lake). Used only on Titan. | IN | |
| Labes, labēs | , | Landslide debris. Used only on Mars and 1 Ceres. | LA | |
| Labyrinthus, labyrinthi | , | Complex of intersecting valleys or ridges. | LB | |
| Lacuna, lacunae | , | Irregularly shaped depression having the appearance of a dry lake bed. Used only on Titan. | LU | |
| Lacus, lacūs | A "lake" or small plain on Moon and Mars; on Titan, a "true lake" of dark liquid hydrocarbons or a small, dark plain with discrete, sharp boundaries; on Pluto, a small isolated glacier | LC | ||
| Landing site name | Lunar features at or near Apollo landing sites | LF | ||
| Large ringed feature | Cryptic ringed features | LG | ||
| Lenticula, lenticulae | , | Small dark spots on Europa | LE | |
| Linea, lineae | , | Dark or bright elongate marking, may be curved or straight | LI | |
| Lingula, lingulae | , | Extension of plateau having rounded lobate or tongue-like boundaries | LN | |
| Lobus | Lobes of contact binaries. Currently used only on Arrokoth. | LO | ||
| Macula, maculae | , | Dark spot, may be irregular | MA | |
| Mare, maria | , | A "sea": on the Moon, a low albedo, relatively smooth plain, generally of large extent; on Mars, dark albedo area, e.g. Mare Erythraeum; on Titan, large expanses of dark materials thought to be liquid hydrocarbons, e.g. Ligeia Mare. | ME | |
| Mensa, mensae | , | A flat-topped prominence with cliff-like edges, i.e. a mesa. | MN | |
| Mons, montes | , | Mons refers to a mountain. Montes refers to a mountain range. | MO | |
| Oceanus | Very large dark area. The only feature with this designation is Oceanus Procellarum. | OC | ||
| Palus, paludes | , | "Swamp"; small plain. Used on the Moon and Mars. | PA | |
| Patera, paterae | , | Irregular crater, or a complex one with scalloped edges e.g. Ah Peku Patera. Usually refers to the dish-shaped depression atop a volcano. | PE | |
| Planitia, planitiae | , | Low plain e.g. Amazonis Planitia. | PL | |
| Planum, plana | , | A plateau or high plain e.g. Planum Boreum. | PM | |
| Plume, plumes | A cryovolcanic feature on Triton. This term is currently unused. | PU | ||
| Promontorium, promontoria | , | "Cape"; headland. Used only on the Moon. | PR | |
| Regio, regiones | , | Large area marked by reflectivity or color distinctions from adjacent areas, or a broad geographic region | RE | |
| Reticulum, reticula | , | reticular (netlike) pattern on Venus | RT | |
| Rima, rimae | , | Fissure. Used only on the Moon and 21 Lutetia. | RI | |
| Rupes, rupēs | , | Scarp | RU | |
| Saxum, saxa | , | Boulder or rock | SA | |
| Satellite feature | A feature that shares the name of an associated feature, for example Hertzsprung D. | SF | ||
| Scopulus, scopuli | , | Lobate or irregular scarp | SC | |
| Serpens, serpentes | , | Sinuous feature with segments of positive and negative relief along its length | SE | |
| Sinus, sinūs | "Bay"; small plain on Moon or Mars, e.g. Sinus Meridiani; On Titan, bay within bodies of liquid. | SI | ||
| Sulcus, sulci | , | Subparallel furrows and ridges | SU | |
| Terra, terrae | , | Extensive land mass e.g. Arabia Terra, Aphrodite Terra. | TA | |
| Tessera, tesserae | , | An area of tile-like, polygonal terrain. This term is used only on Venus. | TE | |
| Tholus, tholi | , | Small domical mountain or hill e.g. Hecates Tholus. | TH | |
| Undae, undae | A field of dunes. Used on Venus, Mars and Titan. | UN | ||
| Vallis, valles | , | A valley e.g. Valles Marineris. | VA | |
| Vastitas, vastitates | , | An extensive plain. The only feature with this designation is Vastitas Borealis. | VS | |
| Virga, virgae | , | A streak or stripe of color. This term is currently used only on Titan. | VI | |
All but three features on Venus are named after female personages (goddesses and historical or mythological women). These three exceptions were named before the convention was adopted, being respectively Alpha Regio, Beta Regio, and Maxwell Montes which is named after James Clerk Maxwell.
See also: Selenography, List of features on the Moon, List of craters on the Moon, List of maria on the Moon, List of mountains on the Moon and List of valleys on the Moon.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Craters are generally named after deceased scientists, scholars, artists and explorers who have made outstanding or fundamental contributions to their field. Additionally, craters in or around Mare Moscoviense are named after deceased Russian cosmonauts and craters in and around Apollo crater are named after deceased American astronauts (see Space accidents and incidents). This convention may be extended if other space-faring countries suffer fatalities in spaceflight. | |
| Lacūs, Maria, Paludes, Sinūs | These features are assigned names which are Latin terms describing weather and other abstract concepts. | |
| Montes | Montes are named after terrestrial mountain ranges or nearby craters. | |
| Rupēs | Rupēs are named after nearby mountain ranges (see above). | |
| Valles | Valles are named after nearby features. | |
| Others | Features that don't fall into any of the above categories are named after nearby craters. |
| Feature type | Naming convention | |
|---|---|---|
| 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. See Classical albedo features on Mars for a list. |
When space probes have landed on Mars, individual small features such as rocks, dunes, and hollows have often been given informal names. Many of these are frivolous: features have been named after ice cream (such as Cookies N Cream); cartoon characters (such as SpongeBob SquarePants and Patrick); and 1970s music acts (such as ABBA and the Bee Gees).[3]
Features on Deimos are named after authors who wrote about Martian satellites. There are currently two named features on Deimos Swift crater and Voltaire crater after Jonathan Swift and Voltaire who predicted the presence of Martian moons.
All features on Phobos are named after scientists involved with the discovery, dynamics, or properties of the Martian satellites or people and places from Jonathan Swift's Gulliver's Travels.
People and places associated with the Amalthea myth.
Features on Thebe are named after people and places associated with the Thebe myth. There is only one named feature on Thebe Zethus Crater.
See also: List of geological features on Io and List of mountains on Io.
| Feature type | Naming convention | |
|---|---|---|
| Active eruptive centers | Active volcanoes on Io are named after fire, sun or thunder gods or heroes. | |
| Catenae | Crater chains are named after Sun gods. | |
| Fluctūs | Names of fluctūs are derived from a nearby named feature, fire, sun, thunder or volcano gods, goddesses and heroes or mythical blacksmiths. | |
| Mensae, Montes, Plana, Regiones and Tholi | These features can be named after places associated with Io mythology, derived from nearby named features, or places from Dante's Inferno | |
| Paterae | Paterae on Io are named after fire, sun, thunder or volcano gods, heroes or goddesses or mythical blacksmiths. | |
| Valles | Names of valleys are derived from nearby named features. |
See also: List of geological features on Europa, List of craters on Europa and List of lineae on Europa.
| Feature type | Naming convention | |
|---|---|---|
| Chaos | Places associated with Celtic myths | |
| Craters | Celtic gods and heroes | |
| Flexūs | 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 |
See also: List of geological features on Ganymede.
| Feature type | Naming convention | |
|---|---|---|
| Catenae, craters | Gods and heroes of ancient Middle Eastern civilizations | |
| Faculae | Places associated with Egyptian myths | |
| Fossae | Gods (or principals) of ancient Fertile Crescent people | |
| Paterae | Paterae on Ganymede are named after wadis in the Middle East. | |
| Regiones | Astronomers who discovered Jovian satellites | |
| Sulci | Places associated with myths of ancient people |
See also: List of geological features on Callisto and List of craters on Callisto.
| Feature type | Naming convention | |
|---|---|---|
| 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)
See also: List of geological features on Mimas. People and places from Malory's Le Morte d'Arthur legends (Baines translation)
See also: List of geological features on Enceladus. People and places from Burton's Arabian Nights
See also: List of geological features on Tethys. People and places from Homer's Odyssey
See also: List of geological features on Dione. Locations from Roman mythology, or people and places from Virgil's Aeneid
See also: List of geological features on Rhea. People and places from creation myths
See also: List of geological features on Titan.
| Feature type | Naming convention | |
|---|---|---|
| Albedo features, terrae | Sacred or enchanted places, paradise, or celestial realms from legends, myths, stories, and poems of cultures from around the world | |
| Colles | Names of characters from Middle-earth, the fictional setting in fantasy novels by English author J.R.R. Tolkien (1892–1973) | |
| Craters and ringed features | Gods and goddesses of wisdom | |
| Facula and faculae | Facula: Names of islands on Earth that are not politically independent, Faculae: Names of archipelagos | |
| Fluctūs | Gods and goddesses of beauty | |
| Flumina | Names of mythical or imaginary rivers | |
| Freta | Names of characters from the Foundation series of science fiction novels by American author Isaac Asimov (1920–1992) | |
| Insulae | Names of islands from legends and myths | |
| Lacūs and lacunae | Lakes on Earth, preferably with a shape similar to the lacus or lacuna on Titan | |
| Mare and maria | Sea creatures from myth and literature | |
| Montes | Names of mountains and peaks from Middle-earth, the fictional setting in fantasy novels by English author J.R.R. Tolkien (1892–1973) | |
| Planitiae and labyrinthi | Names of planets from the Dune series of science fiction novels by American author Frank Herbert (1920–1986) | |
| Sinūs | Names of terrestrial bays, coves, fjords or other inlets | |
| Undae | Gods and goddesses of wind | |
| Virgae | Gods and goddesses of rain |
See also: List of geological features on Hyperion. Sun and Moon deities
See also: List of geological features on Iapetus. People and places from Sayers' translation of Chanson de Roland; the only exception is Cassini Regio, which is named after its discoverer, Giovanni Cassini.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Craters of Phoebe are named after people associated with Phoebe or people from Argonautica by Apollonius Rhodius or Gaius Valerius Flaccus. | |
| Other | Non-crater features on Phoebe are named after places from Argonautica. |
Satellites of Uranus are named for characters from the works of William Shakespeare or from The Rape of the Lock.
Mischievous (Pucklike) spirits (class)
See also: List of geological features on Miranda. Characters, places from Shakespeare's plays
See also: List of geological features on Ariel. Light spirits (individual and class)
Dark spirits (individual)
See also: List of geological features on Titania. Female Shakespearean characters, places
See also: List of geological features on Oberon. Shakespearean tragic heroes and places
There are currently no named features on Uranian small satellites, however the naming convention is heroines from plays by Shakespeare and Pope.
Features on Proteus are to be named after water-related spirits, gods or goddesses who are neither Greek nor Roman. The only named feature on Proteus is crater Pharos.
See also: List of geological features on Triton. Geological features on Triton should be assigned aquatic names, excluding those which are Roman and Greek in origin. Possible themes for individual descriptor terms include worldwide aquatic spirits, famous terrestrial fountains or fountain locations, terrestrial aquatic features, famous terrestrial geysers or geyser locations and terrestrial islands.
There are currently no named features on Nereid. When features are discovered, they are to be named after individual nereids.
Features on other satellites of Neptune, once discovered, should be named after gods and goddesses associated with Neptune/Poseidon mythology or generic mythological aquatic beings.
In February 2017, the IAU approved the following themes for surface features on Pluto and its satellites:[4] [5]
See main article: article, Geography of Pluto and List of geological features on Pluto.
See main article: article, Geography of Charon and List of geological features on Charon.
See also: List of geological features on Ceres.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Agricultural deities | |
| other | Agricultural festivals |
See also: List of geological features on Vesta.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Historical and mythological women of Ancient Rome (in one case, Angioletta, a modern-day female scientist who lived in Rome) | |
| other | Festivals of Ancient Rome |
See also: List of geological features on 243 Ida and Dactyl.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Caverns and grottos of the world | |
| Dorsa | Galileo project participants | |
| Regiones | Discoverer of Ida and places associated with the discoverer |
See also: List of geological features on 951 Gaspra.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Spas of the world | |
| Regiones | Discoverer of Gaspra, and Galileo project participants |
See also: List of craters on 253 Mathilde.
See also: List of geological features on 433 Eros.
| Feature type | Naming convention | |
|---|---|---|
| Craters | Mythological, literary, and historical names of lovers | |
| Regiones | Discoverers of Eros | |
| Dorsa | Scientists who have contributed to the exploration and study of Eros |