Planetary nomenclature

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. The task of assigning official names to features is taken up by the International Astronomical Union since its founding in 1919. [cite web|url=http://planetarynames.wr.usgs.gov/history.html|title=History of Planetary Nomenclature|date=17/05/2008]

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 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:

#Nomenclature is a tool and the first consideration should be to make it simple, clear, and unambiguous.
#Features with longest sides below are not assigned official names unless they have exceptional scientific interest.
#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.
#Duplication of the same name on two or more bodies is to be avoided.
#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.
#Where possible, the themes established in early solar system nomenclature should be used and expanded on.
#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.
#No names having political, military or religious significance may be used, except for names of political figures prior to the 19th century. (Note: Apparently this only goes for religions that are widely practiced today, since gods and goddesses of ancient religions are obviously acceptable to the IAU.)
#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.
#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.
#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 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.

Descriptor terms (feature types)

The Moon

=Europa=

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 d'Arthur" 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=

(243) Ida I Dactyl

433 Eros

References

* The above article were adapted from the public domain work United States Geological Survey [http://planetarynames.wr.usgs.gov/ Gazetteer of Planetary Nomenclature]
* "Mapping and Naming the Moon: A History of Lunar Cartography and Nomenclature", E. A. Whitaker, 1999, ISBN 0-521-62248-4.

ee also

* Astronomical naming conventions
* Geological features of the solar system
* Naming of moons
* Selenography

Further reading

*cite book|title=Planetary Mapping|author=Ronald Greeley and Raymond M. Batson|publisher=Cambridge University Press|date=1990|isbn=052103373X

External links

* [http://www.planetary.org/blog/article/00000691/ 'Planetary Names: How do we come up with them?'] , Planetary Society weblog article by Rosaly Lopes, IAU WGPSN member
* [http://planetarynames.wr.usgs.gov/append2.html Members of the WGPSN]
* [http://emc.elte.hu/~hargitai/hargitai/planmaps.pdf Planetary Maps: Visualization and Nomenclature] Cartographica 41/2 2006
* [http://emc.elte.hu/~hargitai/hargitai/topomdrs.pdf Development of a Local Toponym System at the Mars Desert Research Station] Cartographica 42/2 2007