On our planet, almost all features—seas, rivers, mountains—have names. Many, named like this since the first civilizations. But what about the other celestial bodies? Many were nothing more than a tiny point of light in the eyepiece of a telescope until they received a visit from a space probe that revealed their immense variety of landscapes. The International Astronomical Union (IAU), the body responsible for planetary nomenclature, has just launched a public contest to collaborate in the baptism of planets outside our solar system, the exoplanets. Up to 20 exoworlds, among the first to be targets of the James Webb telescope, are now available to contribute ideas from schools, astronomy enthusiasts and the general public. But it was not always possible to resort to this popular participation.
The toponymy of the Moon was established as early as the 17th century, thanks to the work of the Jesuit Giovanni Battista Riccioli. Before him, other cartographers had put forward other proposals, generally in a clear attempt to curry favor with the ruler of the day. Galileo himself had baptized Jupiter’s satellites as “Medicean stars”, in reference to his patron Cosimo II de’ Medici. Around the same time, in England, a competitor of Galileo named Thomas Harriot named one of the lunar plains Britannia. And in the Spain of Felipe III, the royal cosmographer Michael van Langren composed a selenite map studded with national names, from the Philippine Ocean to the Austrian Sea, along with dozens of court figures.
In the height of optimism, van Langren adds a caption to his map in which he “prohibits, by royal provision, changing any name on this map under a fine of three guilders.” Warning that it would not have much success because in 1647, Hevelius —on the Protestant side— publishes another selenography inspired by the Central European dynasties. And four years later, Riccioli and Grimaldi present another version, with a new nomenclature, in which, by the way, they include the names of quite a few companions of their order.
At least, Riccioli established a systematic criterion: the great plains or “seas” would receive names of states of the spirit (Tranquillitatis, Serenitatis, Crisium…); the mountains, those of the Earth’s mountain ranges, and the craters would be dedicated to deceased figures of science. That criterion holds today, even in the hidden hemisphere, which was not photographed until 1959 by a Soviet probe. And in which, of course, Russian names abound.
The Martian nomenclature respects that established by Giovanni Schiaparelli, based on places from classical antiquity: many plains, mountains and canals that he thought he perceived through his telescope did not correspond to any real accident: they were simple optical illusions or the result of changes in brightness caused by large dust storms. But the names of the regions remain.
Thus, on Mars we have references to a “land of Gold” (Chryse), classical Greece (Hellas) or the magical fountain (Acidalia) where the three Graces bathed. Some names have been appropriate, such as Nix Olympica (Olympus levels) which turned out to be an annular cloud anchored on the top of Mount Olympus, the largest volcano in the entire Solar System. Or the Coprates Canal, named after a river in ancient Persia. Photos taken in 1971 showed that its position on the map coincided with the huge equatorial canyon that crosses half the planet. Today its official name has changed to Valles Marineris, in memory of the orbiting probe that discovered it.
Mount Marilyn is located between the Sea of Tranquility and the Sea of Fecundity and was named by astronaut James Lovell in honor of his wife.NASA/GSFC/LROC School of Earth a
The appearance of the surface of Mercury and Venus was a complete mystery until well into the 1970s. The first, due to its remoteness and small size; Venus, due to the thick layer of clouds that covers it and that means that the only way to cross it is by radar.
Venus has a pair of continents, highlands that rise above endless volcanic plains. All its features are given female names, whether mythological or real characters: Isthar, Aphrodite, Atalanta… The large craters (over 20 kilometers) are dedicated to famous personalities, from empresses to painters, doctors or dancers. The little ones simply have women’s names in all the languages of the world. Almost a thousand, in all.
On the entire planet there is only one exception: the highest mountain is dedicated to James Maxwell, in recognition of his formulation of electromagnetism. The radar that made it possible to lift the veil of clouds on Venus is a direct application of these studies.
The IAU decided to name the craters of Mercury (and there are many) in homage to plastic artists, musicians and writers of all times. Also scientists, like the Nazi physicists who had to withdraw the honor two years ago. Some special features bear equally original names: the faults and escarpments are dedicated to exploration ships, such as the Santa María de Colón, the Endurance de Cook or the Victoria de Magallanes. The chains of craters, named after radio telescopes, which were the first instruments to study the relief of the planet. And certain areas of the land brighter than the rest share a common name: “Serpent” in dozens of languages, from Amharic to Zulu.
Map of the planetary systems that will be named through public competition.IAU OAO/NARIT/M. Tangmatithan
As spacecraft explored new planets, the IAU’s job became more and more complicated. In 2019, the campaign to get Rosalía de Castro to name the star HD 149143, 240 light years from Earth, and for the planet that orbits it to be called Río Sar, a Coruña tributary of the Ulla, was a social phenomenon in Galicia. which was sung by the Galician writer. They finally succeeded, as happened in 2015, when Cervantes became a star by vote along with his four planets: Quixote, Rocinante, Sancho and Dulcinea. Increasingly, the UAI demands that the candidacies be culturally diverse names, that favor the visibility of the indigenous wealth of the nations.
Giants and swarms
Gas giants lack a solid surface, but the swarms of satellites they possess do not. Jupiter and Saturn have around 80; Uranus, two dozen; and Neptune, one. Each one, with its peculiar topography, its mountains, furrows, craters, plains and ravines. It was necessary to use all known mythologies, from Norse legends to Maori traditions. The UAI acknowledges having consulted so far more than 600 encyclopedias, astrological dictionaries and references from all cultures. But the collection was not infinite, so it was necessary to define very rigorously what myths would be reserved for each celestial body.
Io, Jupiter’s volcanic satellite, was appropriately dedicated to gods of fire and thunder, as well as characters confined in Hell from The Divine Comedy. Europe has a monopoly on Celtic myths; Ganymede, the one of Mesopotamian divinities and heroes and for the frigid Callisto made use of the Inuit legends.
To establish the toponymies of the satellites of Saturn, it was necessary to be very restrictive, on pain of risking exhausting the supply of names. Thus, each was assigned a theme in the form of an epic. The Mimas craters are inspired by the knights of Arthurian legend; in Tethis and Dione the Odyssey and the Aeneid are used and in Enceladus, the tales of the Arabian Nights (the four southern fissures from which its famous geysers sprout are called Damascus, Baghdad, Cairo and Alexandria). As for Iapetus, whose morphology is unique (one snow-white hemisphere and the other, black as coal), its craters take the name of characters from The Song of Roland, albeit well segregated: the French on the light side and the Saracens in the dark
hodgepodge of novels
Titan, by far the oldest of them all, is assigned a certain hodgepodge of names that combines protagonists of fantasy novels (Dune, The Lord of the Rings or the Foundation trilogy) with mythical sea beasts, such as the Kraken lake or divinities of wind and rain. This last criterion is also very appropriate, since Titan is the only known world in which it rains. Not water, certainly, but hydrocarbons; but rain after all.
For the satellites of Uranus, a generic criterion was also adopted: characters from the works of Shakespeare and Alexander Pope. There we find all the protagonists of The Tempest: goblins, elves, fairies… and also universal characters such as Hamlet, Macbeth and King Lear. The little satellite Miranda contains numerous references to the tragedy of Romeo and Juliet, in particular the inconceivable cliff of Verona, with its twenty-kilometre drop-to-peak ice wall.
There is little photographic coverage of Neptune and its satellites, which, for now, gives cartographers some breathing space. All names in this family refer to spirits of rivers and seas. Not just Greco-Latin. There is Akupara, the tortoise from Hindu mythology on whose shell rest the four elephants that support the world, or Namazu, the monstrous Japanese fish that triggers earthquakes with the force of its tail.
Finally, there is the growing family of dwarf planets, asteroids and comets. Pluto is themed with references to gods of the underworld, but given the complex morphology revealed by the New Horizons probe, room had to be made for more modern names based on real or science fiction scientists and exploration ships. One of its great ice deserts is the Sputnik Plain. And among the craters of its Charon satellite are those dedicated to Captain Kirk, Mr Spock, Lieutenant Ripley from Alien, Luke Skywalker and Darth Vader himself. None of them are official. Yet.
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