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 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:
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.
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.
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 clustersChaos 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
structuresFlexus, flex\-us A very low curvilinear ridge with a FE
scalloped patternFluctus, 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
sitesLarge 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 straightMacula, 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
edgesMons, 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 edgesPlanitia, planitiae Low plain PL Planum, plana Plateau or high plain PM Plume PU Promontorium(1), "Cape"; headland PR
promontoriaRegio, regiones A large area marked by reflectivity or RE
color distinctions from adjacent areas, or a broad geographic regionReticulum, 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
namesDorsa 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 cratersLac\-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 MarsSmall 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 mapsDEIMOS Authors who wrote about martian satellites PHOBOS Scientists involved with the discovery, dynamics,
or properties of the martian satellites
SATELLITES OF JUPITER
AMALTHEA People and places associated with the Amalthea myth
THEBE People and places associated with the Thebe myth
IO 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 blacksmithsMensae People associated with Io myth, derived from
nearby feature, or from Dante's InfernoMontes Places associated with Io myth, derived from
nearby feature, or from Dante's InfernoPaterae Fire, sun, thunder, volcano gods, heroes, goddesses,
mythical blacksmithsPlana Places associated with Io myth, derived from
nearby feature, or from Dante's InfernoRegiones Places associated with Io myth, derived from
nearby feature, or from Dante's InfernoTholi 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 Nights TETHYS People and places from Homer's Odyssey DIONE People and places from Virgil's Aeneid RHEA People and places from creation myths TITAN Ancient displaced cultures HYPERION Sun and Moon deities IAPETUS 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 plays ARIEL Light spirits (individual and class) UMBRIEL Dark spirits (individual) TITANIA Female Shakespearean characters, places OBERON Shakespearean tragic heroes and places SMALL 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 nereids SMALL 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