What's in a Name on the Planets?

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay


Early observers thought the dark plains on the Moon were seas and lakes and gave themnames like Mare Tranquillitatis (Sea of Tranquillity, where Apollo 11landed). We retain those traditional names even though, of course, we know they are notseas. (The terms Lacus, "lake" and Mare, "sea" have now been applied to true bodies of liquid on Titan.)

In the 1600's, the Italian astronomer Giovanni Riccioli began the custom of namingcraters on the Moon for great astronomers. A large crater was later named for Ricciolihimself. There's almost a perverse, inverse relationship between the size of a crater andthe astronomer's contribution to lunar studies. Great as Plato, Tycho, and Copernicus are,they did not advance our understanding of the Moon much, but they have some of the largestand most conspicuous craters named for them. (By the time telescopes were powerful enoughto allow serious research on the Moon, all the good craters were taken!)

Planetary probes revealed that there are far more craters than astronomers, great andotherwise, so names of objects on other planets are derived from other biographicalcategories or mythology. A commission of the International Astronomical Union overseesnaming, and the names (so far) are recognized by the various spacefaring nations. Therules are:

Planetary geographical features have Latin names. Latin is traditional, apolitical, andthe closest thing to a universal language in history. The following are in use, with theliteral Latin translation in parentheses, followed by the geographical meaning.



Australis, Meridionalis - South
Borealis, Septentrionalis - North

Naming Conventions on the Planets

The U.S. Geological Survey site, Gazetteer of Planetary Nomenclature,gives a complete listing of naming conventions. The main themes are listed here.


Inventor of the lyre in Greek mythology, hence craters named for great figures in thearts. Large regions are named for deities equivalent to Mercury.


Female figures in history and mythology


Some traditional names were given by Earth-based observers and are preserved, sometimes with appropriate modifications. For example, the white spot Nix Olympica (the snows of Olympus) is now known to have been a cloud cap over the volcano Olympus Mons. Some large craters were named early onfor famous scientists. Small craters named for cities and towns on Earth.


The moons of Jupiter presented astronomers with a brand new problem. They were the first completely new objects ever discovered in the Solar System. Galileo, who knew a marketing opportunity when he saw one, wanted to name themThe Medicean Stars, after the powerful Medici family that ruled Florence, and who would presumably support Galileo handsomely. German astronomer Simon Marius proposed the names we now use.

The names should obviously be connected to Jupiter, yet subordinate. If you're familiar with mythology, you realize this definitely rules out Hera, or Juno, Jupiter's jealous wife (anyway, a large asteroid bears the name Juno). Her main hobby was breaking up Jupiter's innumerable love affairs and inflicting vengeance on the lovers. So satellites of Jupiter are named for figures with whom Jupiter had love affairs. Jupiter worked industriously to keep astronomers well supplied with names for satellites. However, not even Zeus was able to keep up with the tally of satellites (he tried!) and newly discovered satellites may also be named for offspring of Zeus and other mythological figures.

Incidentally, Ganymede was a boy. The Greeks were fairly tolerant of such things. The four largest satellites and the naming conventions used on each are:



Uranus is the only body in the Solar System with moons not named fromclassical mythology - its moons are named from works by Shakespeare andAlexander Pope. Any future satellites will follow that naming convention. 


Neptune, god of the sea, has satellites named for minor deities connectedwith sea myths. Features on Triton have aquatic names.


Features on Pluto will be drawn from underworld myths.

Minor Planets

Names of minor planets rapidly ran out of mythological characters and nowinclude cities, observatories, people (the dead Challenger and Columbiaastronauts among them) and many other things. The minor planets with namedfeatures typically follow some theme associated with the name of the minorplanet itself. 951 Gaspra, named after a European spa, has craters named after spas,and so on. Having some class of features named after people involved in mappingthe body is also common. 433 Eros, named after the Greek god of love, will have cratersnamed after famous erotic figures. Before you nominate yourself, bear in mindthat features cannot be named after living people.

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Created 20 May 1997, Last Update 1 November 1999