Thousands of craters, mountains and valleys on the Moon, Mercury, Venus and Mars are named after people. I traced 2,718 of those names back to Earth, to the towns where the people they honour were born. Click a crater and fly to its namesake's home town.
Look up at the Moon and you are looking at a map of Europe. Not the shapes, but the names. Copernicus, Tycho, Kepler, Plato: the great craters of the near side carry the names of astronomers and philosophers, most of them born within a few days' ride of each other. Since the seventeenth century, when the Jesuit astronomer Giovanni Battista Riccioli gave many of them the names they still have, we have gone on naming the features of other worlds after people. The International Astronomical Union now keeps the list, with a rule for each world: Mercury's craters go to artists, writers and composers, Venus's features to women, and Mars's small craters to the villages of Earth.
Wikidata, the open database behind Wikipedia, records what most of these features are named after, and where most of those people were born. I joined the two: 3,471 named features on the Moon, Mercury, Venus and Mars, 2,718 of them named after 2,560 people, linked to 1,661 birthplaces on Earth. The question is a simple one. When we name another world after people, whose world is it?
On the left is the world you choose; on the right, Earth. Each dot on the left is a named feature, coloured by where its namesake was born; each dot on the right is a birthplace, sized by how many features it has. Click either and the other map follows.
Positions from Wikidata, on each world's own longitude and latitude (east positive). Web maps cannot show the poles, so features beyond 85 degrees are drawn at the edge. Grey rings on the left are features named after something other than a person, such as a village, a ship or a word. Open red circles on the right (on by default) are the places on Earth that features on the chosen world are named after. Imagery for the Moon and Mars (in the layers panel): OpenPlanetaryMap basemaps (OpenPlanetary), from NASA and USGS data. Earth: the Inked World map style on OpenStreetMap data via OpenFreeMap.
Of the 1,548 lunar features named after a person whose birthplace Wikidata knows, 1,165 (75%) honour someone born in Europe, and 250 (16%) someone born in North America. Asia has 102, 58 of them born before 1500: the Greek scholars of Anatolia (Turkey has 32) and the astronomers of the Islamic world. China has 15. Africa has 19, 12 of them in Egypt, above all the scholars of ancient Alexandria; South America has 6 and Oceania 6. Paris alone, with 38, outnumbers those three continents together.
Where the namesakes were born, by world
Share of features named after a person with a known birthplace, by the modern continent of that birthplace. Hover a block.
The other worlds, named later and under newer rules, are wider. Mercury is the least European: 55% of its namesakes were born in Europe and 20% in Asia, because the rule for its craters, artists, writers and composers, reaches into Japanese, Chinese and Indian art in a way that the history of astronomy, as told in the West, does not. Venus has 61% and Mars 65%. Across all four worlds, 69% of the people with a known birthplace were born in Europe, in 104 modern countries in all.
By modern country the Moon is shared between four: the United States (15%), Germany (13%), the United Kingdom (12%) and France (11%), then Italy and Russia. Germany, France and Britain together hold 36% of the Moon's people. India has 10 and Japan 9. On Venus and Mars the United States leads by more: 23% and 28%.
The top countries on each world
Share of features named after a person with a known birthplace, by the modern country of that birthplace. Hover a bar.
Half of the Moon's people were born before 1838. The Moon carries the oldest names: 178 of its features honour people born before 1500, from Thales and Anaximander to Ptolemy, al-Battani and Ulugh Beg. But its biggest cohort was born in the nineteenth century, the age of the great observatories. The median person on Mercury was born in 1820, on Venus in 1852 and on Mars in 1862.
Namesakes by century of birth
Features named after a person with a known date of birth, by the century of that birth. Hover a column.
On the Moon 52% of namesakes were astronomers and another 40% other scientists, mathematicians or engineers. Mercury is the mirror image: 90% were writers, artists or musicians first, and 98% had at least one such occupation, as the rule for its craters asks. Venus has the IAU's rule that its features honour women, real or mythical: its craters are named after famous women, from Sappho and Cleopatra to Rachel Carson and Margaret Mead, so it is the only world here where politicians, queens and saints appear in any number (10%).
What the namesakes did
Each person in one group: the first that any of their Wikidata occupations falls in, in the order of the legend; people with no occupation recorded are left out. Hover a block.
Venus is a world of women by rule: all but one of its 412 features named after a person with a recorded sex honour a woman (99.8%); the exception is Maxwell Montes, named after James Clerk Maxwell before the rule was set. Leave Venus aside and the picture is stark. On the Moon only 45 of 1,614 namesakes are women (2.8%), among them Hypatia, Hildegard of Bingen, Lise Meitner, Emmy Noether and Valentina Tereshkova. Mars has 5.5% and Mercury, with its artists and writers, 17.8%. Across the three worlds it is 6.0%.
The share rises with birth date, because the names honour the dead and women were long shut out of science: 2.6% of namesakes born before 1800 on these three worlds are women, 4.8% of those born in the 1800s, 16.7% of those born from 1900 to 1939 and 30.9% of the 42 born in 1940 or later, among them the astronauts Judith Resnik, Christa McAuliffe, Kalpana Chawla and Laurel Clark.
Women among the namesakes
Share of features named after a person recorded in Wikidata as female, among those recorded as female or male, by world (left) and, for the Moon, Mercury and Mars together, by period of birth (right). Hover a bar.
The Moon always turns the same face to Earth. Nobody saw the other side until the Soviet probe Luna 3 photographed it in 1959, and most of its features were named in the following years, many after Soviet proposals. You can see it in the birthplaces. On the near side, 3% of namesakes were born in the former Soviet Union; on the far side, 20%, 5.7 times as many. The far side's people are also younger (the median was born in 1874, against 1784 on the near side), more often American (20% against 11%), and include 35 astronauts and cosmonauts, among them Yuri Gagarin, Valentina Tereshkova and the crews lost on Apollo 1, Challenger and Columbia.
The two faces of the Moon
Every feature named after a person, on the near side (left) and the far side (right), coloured by the modern continent of the birthplace; dots with a heavy black ring mark people born in the former Soviet Union. Hover a dot.
On the far side, one name in five belongs to someone born in the former Soviet Union. On the near side, one in 29.
The 1,661 birthplaces are led by the capitals of science. Paris has 69 features across the four worlds (38 on the Moon), London 40, Saint Petersburg 37 and Moscow 29. Click a row to find the town on the map.
Birthplaces with the most features
Features on each world named after people born there. Click a row.
135 people are honoured on more than one world, mostly astronomers with a crater on both the Moon and Mars. Only Giovanni Schiaparelli, Gerard Kuiper and E. M. Antoniadi are on three.
Mars has a different rule for its small craters: they are named after towns and villages on Earth with fewer than 100,000 people. Wikidata gives the place and its coordinates for 279 Martian features, 217 of them towns and villages, in 102 countries. Turn on the layer on the Earth map, or pick Mars and click a grey ring. These places are far more evenly spread than the people of Mars: 30% are in Europe against 65% of Mars's namesakes, 30% are in Asia and 11% in Africa. The United States has most (31), then India (17) and China (16); Britain's include Crewe, Corby, Maidstone and Kilkhampton. The Moon has a handful of Earth's places too, mostly its mountain ranges, named after the Alps, the Apennines, the Carpathians and the Caucasus.
Where the Mars place names come from
Martian features named after a place on Earth, by continent, beside the continents of birth of the people Mars's features are named after. Hover a block.
Data. Everything comes from Wikidata (CC0), queried through the QLever engine: every item with coordinates on the Moon, Mercury, Venus or Mars that has a "named after" (P138) statement, with the namesake's birthplace (P19), the birthplace's coordinates and country, dates of birth and death, and occupations. I removed the duplicate rows the query makes for every type and occupation, and left out map quadrangles, which are named after a feature on them. That leaves 3,471 features, 40 of them named after more than one person. A person with two birthplaces in Wikidata (52 people) keeps the first with coordinates. Sex comes from a second Wikidata query (property P21); shares of women are among people recorded as female or male. Places on Earth that features are named after come from a third query, keeping namesakes with coordinates on Earth and leaving out languages.
Countries and continents. Each birthplace is placed in its modern country and continent (Natural Earth) by its coordinates, so Ptolemy counts for Egypt and Hilbert, born in Königsberg, for Russia. "Former Soviet Union" means the fifteen countries that were Soviet republics. 144 of the 2,560 people have no located birthplace and are left out of the shares.
Caveats. Wikidata is not the IAU's Gazetteer of Planetary Nomenclature, the official list. Its coverage of "named after" is good for the Moon and Mercury and patchier for Mars, where most features are named after villages and rivers rather than people (350 of 584 Mars features here, 60%); Wikidata does not give those places' coordinates in this extract, so they are counted but not mapped. Wikidata has errors. It places the Scottish mathematician Colin Maclaurin's birth at a house called The Manse in Australia; I corrected this to Kilmodan in Argyll. I then checked every birthplace that Wikidata gives as a country, empire, state or large region, every birthplace whose Wikidata country disagrees with its map position, every missing name and sex value, and all the Martian features named after places on Earth. 18 birthplaces are corrected (Edna Manley, for example, was born in Bournemouth, not Yorkshire, and Gavriil Tikhov in Belarus, not Kazakhstan); 31 people whose birthplace is only a country or empire, or is disputed, are left off the map rather than placed at a country's centre; 2 sex values, 3 wrong "named after" links, 41 missing names and 10 place links (ships, a spacecraft, a duplicate and country links) are fixed. All are listed in small documented overrides files; some errors will remain. Crimea is counted as part of Ukraine. Occupations are uneven, and the Mars place list is only as complete as Wikidata.