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. How names are approved by the IAU 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. 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: Nomenclature is a tool and the first consideration should be to make it simple, clear, and unambiguous. In general, official names will not be given to features whose longest dimensions are less than 100 meters, although exceptions may be made for smaller features having exceptional scientific interest. The number of names chosen for each body should be kept to a minimum. Features should be named only when they have special scientific interest, and when the naming of such features is useful to the scientific and cartographic communities at large. Duplication of the same surface feature name on two or more bodies, and of the same name for satellites and minor planets, is discouraged. Duplications may be allowed when