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.
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 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.
FEATURE DESCRIPTION DESIG.
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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
structures
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
sites
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
edges
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
promontoria
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
MERCURY
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
VENUS
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)
THE MOON
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
MARS AND MARTIAN SATELLITES
MARS
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
DEIMOS
Authors who wrote about martian satellitesPHOBOS
Scientists involved with the discovery, dynamics, or properties of the martian satellites
SATELLITES OF JUPITER
AMALTHEA
People and places associated with the Amalthea mythTHEBE
People and places associated with the Thebe mythIO
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
EUROPA
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
GANYMEDE
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
CALLISTO
Large ringed features Homes of the gods and of heroes Craters Heroes and heroines from northern myths Catenae Mythological places in high latitudes
SATELLITES OF SATURN
JANUS
People from myth of Castor and Pollux (twins)EPIMETHEUS
People from myth of Castor and Pollux (twins)MIMAS
People and places from Malory's Le Morte Darthur legends (Baines translation)ENCELADUS
People and places from Burton's Arabian NightsTETHYS
People and places from Homer's OdysseyDIONE
People and places from Virgil's AeneidRHEA
People and places from creation mythsTITAN
Ancient displaced culturesHYPERION
Sun and Moon deitiesIAPETUS
People and places from Sayers' translation of Chanson de RolandPHOEBE
People associated with Phoebe, islands of the Greek archipelagos
SATELLITES OF URANUS
PUCK
Mischievous (Pucklike) spirits (class)MIRANDA
Characters, places from Shakespeare's playsARIEL
Light spirits (individual and class)UMBRIEL
Dark spirits (individual)TITANIA
Female Shakespearean characters, placesOBERON
Shakespearean tragic heroes and placesSMALL SATELLITES
Heroines from Shakespeare and Pope
SATELLITES OF NEPTUNE
PROTEUS
Water-related spirits, gods, goddesses (excluding Greek and
Roman names)
TRITON
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.
NEREID
Individual nereidsSMALL SATELLITES
Gods and goddesses associated with Neptune/Poseidon? mythology or generic mythological aquatic beings
PLUTO
Underworld deities
ASTEROIDS
IDA
Craters Caverns and grottos of the world
Dorsa Galileo project participants
Regiones Discoverer of Ida and places associated with the
discoverer
DACTYL
Craters Idaean dactyls
GASPRA
Craters Spas of the world Regiones Discoverer of Gaspra, and Galileo project participants
MATHILDE
Craters Coal fields and basins of the world
EROS
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