Princes, philosophers, astronomers and virtues: short history on the lunar toponymy

Craters or plains, seas and valleys needs to be named as the regions and terrestrial areas. The Moon does not escape from the rules from the sublunary world and the names that are attributed to these formations are always a cultural reflection, even an ideology.

In his rudimentary cartography, William Gilbert proposed descriptive names or evaluated the position of formations: Insula Longa, Sinus Orientalis or Insula Borealis…  In 1645, Van Langren goes even further.

The Dutch selenographer who wished to pay tribute to his sponsors, Philip IV of Spain and Isabella of Bourbon, proposed a toponymy which included Spanish royal family names and from royal European estates: Oceanus Phillipicus, the craters Ferdinand III, Ludovici IV, Christierni IV… Additionally, here comes the arrival of philosophers’ names, mathematicians and explorers. The names of 13 saints are also part of the toponymy, inspired by the terrestrial cartography (Mare Venetum, Venice’s sea for example), also names referring to virtues: Terra Sapientiae (Land of Wisdom), Terra Laboris (Land of Labour), Terra Justitiae (Land of Justice). These names reflect the map’s political dimension, a real reflection of the values of a “right government” during Renaissance, included all attributed princes. Furthermore, we can point out the presence of a Mare Astronomicum, which includes astronomers’ names and Mare Langrenianum and at the border of the crater, Langreni. It is seen as the proof that Van Langren is considering his work’s posterity.

When Johannes Hevelius begins the lunar cartography, he working under the same tradition of Van Langren. He attributes names from virtuous men to the craters and seas, individuals that are deemed to accede the eternity that is promised in the stars. Rapidly, the notices that this option is a dangerous for his work’s posterity. Preferring avoiding controversy and jealousy, he finally chose names from the terrestrial toponymy. It is not surprising if we found in more than 350 000 kilometers away from Earth a Sicilia, a Mare Adriaticum, a Mons Olympus (that we can find on Mars), a Pars Lybiae or a Mare Aegyptiacum.[1]

Afterwards, begins the arrival of Riccioli’s map. The success of the nomenclature from the Jesuit astronomer is important and still to this day, a large part of its toponymy attributed in 1651, are still used. Riccioli gives names to the seas and other regions (lakes, uplands) that are mainly inspired by qualities and virtues, influenced by the theory of moods. Sea of Fecondity, of Crises, of Serenity, Lake of Torments or Lake of Hope are all areas associated to a moral connotation, which is unsurprising in the current context of that period. When naming the craters, the Moon is divided in 8 regions, which is also divided in zones named by philosophers and astronomers. The repartition is chronological, as well geographical: Ancient Greece, Roman Empire, Medieval Europe, Arabic civilization, without omitting Riccioli’s times. Although he was against Copernic’s model, Riccioli pays tribute to his opponents. Hevelius, Kepler, Galileo, Copernic are being attributed craters with important sizes. A few Saints balances this concession made by the supporters of a revised astronomy.[2]

Afterwards, the new added names are modest, since the authors are borrowing Hevelius and Riccioli’s nomenclature, then only Riccioli’s. In 1775, Tobias Mayer keeps the two systems, and then J.H. Shröter only refers to Riccioli. Shröter adds names of scientists posterior to Riccioli, like La Condamine, Maupertuis or Bianchini. In the same process, the new nomenclatures will all complete Riccioli’s by adding the names of astronomers and scientists.

In 1935, the International Astronomical Union, attempts to standardize these varied nomenclatures. The commission, which reunited William Pickering and Mary Blagg (1858-1944), was charged in establishing a final official list of toponyms. The commission took the decision to keep Riccioli’s nomenclature as the foundation of this new norm.[3] Today, the specific names for the lunar landscape are chosen from deceased scientists.

The Paris Observatory keeps in its archives a number of documents that demonstrate the use of these nomenclatures by astronomers during their observations. Here we suggest an excerpt from a collection of field journals from the Observatory of Juvisy, established by Camille Flammarion. Drawings from field journals between May and September 1893 by MM. Quénisset, Rudaux and Guiot are impressive for their esthetic quality and great expression. The texts and legends among those journals are referring to names attributed by the first selenographers, more than 200 years ago.