From Titan's Doom Mons to Mercury's Pourquoi-Pas: how did the landscape of space get its names?

A detail from Ordnance Survey's new map of Mars. Image: OS.

The Ordnance Survey recently made a very nice map of Mars’ Arabia Terra region. This map shows an alien crater-pocketed landscape, peppered with mysterious names like “Aram Chaos”, “Meridiani Planum” and “Marth”.

When the OS makes a map of Britain, it is making a map of a place with history – reflected in place names that come from the many different languages that people have spoken here. But where are the names on the Mars map coming from?

The romance of naming

Space used to be like the Wild West, with different names used by different people. So, in 1911, the International Astronomical Union started to become the official clearing house for space names.

It legitimised features from previous maps (like Schiaparelli’s map of Mars) and made rules for how new names would be picked. It now publishes its database online, and I used this and various NASA maps of other planets to build We Name The Stars – a way of exploring these rules and places.

The IAU conventions seem to understand that there is something magical and important about naming things. We don’t end up with Crater 62 on asteroid BXM-2: each kind of feature (mountains, ridges, craters, lakes) on each different world has a different naming convention, so that similar places are thematically linked. Often revolving around a particular ancient myth, this lends a sense of grandness and history to what is otherwise just some slightly different coloured pixels.

A screenshot from the "We Name the Stars" page on Mars. Click to expand.

Not all names are mythical. Craters on Mercury are named after historically significant artists, while escarpments are named after ships of discovery. This is how you end up with a slope on Mercury named “Pourquoi-Pas”.

Craters on the asteroid Eros are named after “mythological and legendary names of an erotic nature” (which gives us Casanova and Abelard), while Saturn’s moon Titan has places named after mountains in Middle Earth. The largest mountain on Titan is called Doom Mons.

Places We’ll Never Go

Part of the appeal of the OS map is that it reinforces the idea of Mars as a place. It’s a technical challenge, but ultimately we understand how we’d get there, walk around, and get back.

Similarly you can vaguely imagine the 22nd century equivalent of the Arctic Explorer taking the journey my virtual rover is making across the Moon, visiting every crater. But there are plenty of other places to which we’ve given names that will probably never be walked on by people.

Take Mercury – it’s right next to the sun and spins very slowly. Every place on the planet spends every other month staring into the furnace. In several of his books Kim Stanley Robinson solves this problem with Terminator – a city that travels on rails around the planet. The sun heats the rails, which expand and push the city onward – permanently keeping it just beyond dawn.

But this is a fragile solution. Valleys on Mercury are named after ancient abandoned cities – a poor omen for the success of future settlement. Maybe maps of Mercury are for visitors, driving slowly to stay ahead of the sun.


A screenshot from the "We Name the Stars" page on the Moon. Click to expand.

Venus we can’t even visit. In the day the surface can get hot enough to melt lead, and the atmospheric pressure is the equivalent of being a kilometre under the ocean on Earth. On the other hand, it turns out that, if you build floating cities 50km up, the pressure and temperature are pretty much the same as on Earth. To our cloud-dwelling descendants it’ll probably seem odd that we put so many of our goddesses on features as unimportant to them as the floor of the ocean is to us.

There is something strange and wonderful about a system that produces such evocative names for places that in all likelihood no one will ever visit. These names don’t have to be pretty or coherent – but the effort is made anyway.

The European Sky

The IAU was founded at a time when “international cooperation” mostly meant “European cooperation”. The conventions emerging on using old myths and Latinised names were good, because that seemed like common ground.  Astronomers looked into space and then looked back on their shared classical heritage, pillaging the myths of the Romans and Greeks for important sounding but politically neutral names.

Except, of course, it’s not really neutral because not everyone comes from that heritage. Some 60 per cent of feature names are European in origin, and so European myth and history punches a little above its weight in the space naming race.

As the composition of the IAU has changed over time, this shift has been reflected in patterns for future names. Many conventions are now ecumenical: Io is littered with thunder and sun gods from different cultures, and Ceres has features named after the “agricultural festivals of the world”. Rhea uses names from “people and places from creation myths (with Asian emphasis)”; names on Triton are explicitly “aquatic names, excluding Roman and Greek”.

Fragile Monuments

But these are all faraway places, what about European domination of the places we’re actually likely to go – like the Moon and Mars? If the future of space turns out to be non-western, this issue ends up solving itself.

After the Chinese Yutu rover landed on the moon, the landing site was named Guang Han Gong (Moon Palace) and three local craters were given names from Chinese astrology by the IAU. When the asteroid 1998 SF 36 was selected as the target for the Japanese Hayabusa spacecraft, it was designated Itokawa after a Japanese rocket scientist. Where robotic feet go, naming rights follow.

On the Moon there are areas where naming is reserved to honour dead astronauts and cosmonauts, with the ominous note that “this convention may be extended if other space-faring countries suffer fatalities in spaceflight”. And why not? There’s plenty of Moon left, thousands of craters have been identified that have yet to receive an official name.

And even if a feature has a name with a history, will people honour it? Will a Martian Chinese colony in the Rutherford Crater still call it Rutherford? Will Indian settlers in Inuvik keep the name of a small town in Canada – or rename it something closer to home?

There’s a long history of name changes in space. British astronomers carried on with George’s Star (chosen by the discoverer of the planet to honour George III) for many years after everyone else switched to “Uranus”. The Galilean moons were once the ‘Medician stars’ – after the family whose patronage Galileo sought. When Cassini discovered the moons of Saturn he called them ‘the stars of Louis’ after King Louis XIV, hoping to create “a Monument much more lasting than those of Brass and Marble”. That we don’t use any of these names reflects the fragility of monuments that only exist on paper.

European myths may end up the Lingua Franca of empty places – only kept for areas to which no one has any interest in going. If in the future there are settlers in Arabia Terra, that OS map might be an interesting historical artefact for them – a perfectly correct map with all the wrong names. 

You can learn more about space names over at We Name The Stars


Transport for London’s fare zones secretly go up to 15

Some of these stations are in zones 10 to 12. Ooooh. Image: TfL.

The British capital, as every true-blooded Londoner knows, is divided into six concentric zones, from zone 1 in the centre to zone 6 in the green belt-hugging outer suburbs.

These are officially fare zones, which Transport for London (TfL) uses to determine the cost of your tube or rail journey. Unofficially, though, they’ve sort of become more than that, and like postcodes double as a sort of status symbol, a marker of how London-y a district actually is.

If you’re the sort of Londoner who’s also interested in transport nerdery, or who has spent any time studying the tube map, you’ll probably know that there are three more zones on the fringes of the capital. These, numbered 7 to 9, are used to set and collect fares at non-London stations where the Oyster card still works. But they differ from the first six, in that they aren’t concentric rings, but random patches, reflecting not distance from London but pre-existing and faintly arbitrary fares. Thus it is that at some points (on the Overground to Cheshunt, say) trains leaving zone 6 will visit zone 7. But at others they jump to 8 (on the train to Dartford) or 9 (on TfL rail to Brentwood), or skip them altogether.

Anyway: it turns out that, although they’re keeping it fairly quiet, the zones don’t stop at 9 either. They go all the way up to 15.

So I learned this week from the hero who runs the South East Rail Group Twitter feed, when they (well, let’s be honest: he) tweeted me this:

The choice of numbers is quite odd in its way. Purfleet, a small Thames-side village in Essex, is not only barely a mile from the London border, it’s actually inside the M25. Yet it’s all the way out in the notional zone 10. What gives?

TfL’s Ticketing + Revenue Update is a surprisingly jazzy internal newsletter about, well, you can probably guess. The September/October 2018 edition, published on following a freedom of information request, contains a helpful explanation of what’s going on. The expansion of the Oyster card system

“has seen [Pay As You Go fare] acceptance extended to Grays, Hertford East, Shenfield, Dartford and Swanley. These expansions have been identified by additional zones mainly for PAYG caping and charging purposes.

“Although these additional zones appear on our staff PAYG map, they are no generally advertised to customers, as there is the risk of potentially confusing users or leading them to think that these ones function in exactly the same way as Zones 1-6.”

Fair enough: maps should make life less, not more, confusing, so labelling Shenfield et al. as “special fares apply” rather than zone whatever makes some sense. But why don’t these outer zone fares work the same way as the proper London ones?

“One of the reasons that the fare structure becomes much more complicated when you travel to stations beyond the Zone 6 boundary is that the various Train Operating Companies (TOCs) are responsible for setting the fares to and from their stations outside London. This means that they do not have to follow the standard TfL zonal fares and can mean that stations that are notionally indicated as being in the same fare zone for capping purposes may actually have very different charges for journeys to/from London."

In other words, these fares have been designed to fit in with pre-existing TOC charges. Greater Anglia would get a bit miffed if TfL unilaterally decided that Shenfield was zone 8, thus costing the TOC a whole pile of revenue. So it gets a higher, largely notional fare zone to reflect fares. It’s a mess. No wonder TfL doesn't tell us about them.

These “ghost zones”, as the South East Rail Group terms them, will actually be extending yet further. Zone 15 is reserved for some of the western-most Elizabeth line stations out to Reading, when that finally joins the system. Although whether the residents of zone 12 will one day follow in the venerable London tradition of looking down on the residents of zones 13-15 remains to be seen.

Jonn Elledge was the founding editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.