From volcanoes on Mars to scarps on Mercury – how places on other worlds get their names

January 2, 2019 by David Rothery, The Conversation
The solar system’s largest volcano Olympus Mons on Mars, seen by Viking 1. Credit: NASA/JPL

The New Horizons spacecraft, which flew past Pluto in 2015, successfully completed a flyby of "Ultima Thule", an object in the Kuiper belt of bodies beyond Neptune on January 1, 2019. The name Ultima Thule, signifying a distant unknown place, is fitting but it is currently just a nickname pending formal naming. The official names of the body and of the features on its surface will eventually be allocated (this could take years) by the International Astronomical Union (IAU), which celebrates its centenary in 2019.

The IAU's achievements during its first few decades include resolving contradictory sets of names given to features on the Moon and Mars by rival astronomers during the previous few centuries. The nomenclature working group's task would then have been largely over, had the space age not dawned – allowing to send back images revealing spectacular landscape details on planets and their moons.

Planetary scientists would find life difficult without names for at least the largest or most prominent features on a body. If there were no names, the only ways to be sure that other investigators could locate the same feature would be by numbering them or specifying map coordinates. Either option would be cumbersome and unmemorable.

The rules

Building on some of the already entrenched lunar and martian names, the IAU imposed order by establishing themes for the names of features on each body. For example, large craters on Mars are named after deceased scientists and writers associated with Mars (there's an Asimov and a Da Vinci), and craters less than 60km across are named after towns and villages on Earth (there's a Bordeaux and a Cadiz).

The solar system’s largest volcano Olympus Mons on Mars, seen by Viking 1. Credit: NASA/JPL

Apart from craters, most names are in two parts, with a "descriptor term" of Latin origin added to denote the type of feature that has been named. On Mars we find neighbouring valleys called Ares Vallis, Tiu Vallis and Simud Vallis, in which the descriptor term "Vallis" is Latin for valley. This is preceded by the word for "Mars" in a different language – in these examples Greek, Old English/Germanic and Sumerian respectively. Among other descriptor terms are Chasma (a deep, elongated depression), Mons (mountain), Planitia (a low lying plain) and Planum (a high plain or plateau).

Descriptor terms are chosen to avoid implying that we know how any particular feature formed. For example, there are many scarps on Mercury that are currently interpreted as thrust faults (where one region of a planet's surface has been pushed over another). However, a neutral descriptor term – in this case Rupes (Latin for scarp) – is used so they would not have to be renamed if we were to realise that we'd been misinterpreting them. Similarly, none of the giant mountains on Mars that are almost certainly volcanoes has volcano as a formal part of its name.

The largest volcano on Mars, Olympus Mons, coincides with an ephemeral bright spot that can sometimes be discerned through telescopes. Though this was initially dubbed Nix Olympica (meaning "the snows of Olympus") by the 19th-century observer, Giovanni Schiaparelli, space probes have since shown that the temporary brightness is not snow but clouds that sometimes gather around the summit. The IAU decided to keep the Olympus part of the name, qualified by the more appropriate descriptor Mons (mountain in Latin).

On the Moon, the IAU retained Mare (Latin for sea) as a descriptor term for dark spots, even though it is clear they have never been water-filled as was once thought. However, Michael van Langren's Mare Langrenianum, which he immodestly named after himself on his 1655 map, is now Mare Fecunditatis.

From volcanoes on Mars to scarps on Mercury – how places on other worlds get their names
Approved names on global topographic map of Mars. Credit: USGS
Cultural balance

The IAU is rightly sensitive to achieving cultural and gender balance. The names of lunar craters that the IAU inherited commemorate famous past scientists, which for historical reasons are dominantly male and Western. In partial compensation, the IAU decided that all features on Venus, whose surface was virtually unknown because of its global cloud cover until we got radar spacecraft into orbit, would be named after females (deceased or mythical). For example, there is a Nightingale Corona, a large oval-shaped feature named after Florence Nightingale. The only non-female exceptions are three features that had already been named after being detected by Earth-based radar.

Prior to the first detailed images of Jupiter's moons by Voyager-1 in 1979, the IAU planned to use names from the myths of peoples in Earth's equatorial zone for the moon Io. It would use mythical names from the European temperate zone for Europa, names from near-Eastern mythology for Ganymede and names from far northern cultures for Callisto.

They stuck to the latter three, and so Europa has Annwn Regio (a region named after the Welsh "Otherworld"), and Ganymede and Callisto have craters named Anubis (Egyptian jackal-headed god) and Valhalla (Norse warriors' feast hall).

A map of part of Io, with names added. Credit: USGS

However, because Io was revealed to be undergoing continual volcanic eruptions, the original naming theme was deemed inappropriate and was replaced by the names of fire, sun, thunder/lightning and volcano deities from across the world's cultures. For example, the names Ah Peku, Camaxtli, Emakong, Maui, Shamshu, Tawhaki, and Tien Mu (which occur on the map above) come from fire, thunder or Sun myths of the Mayans, the Aztecs, New Britain, Hawaii, Arabia, the Maoris, and China, respectively.

Captain Cook and the Maoris

The IAU has struggled to achieve cultural balance for some features. For example, the theme for Rupes on Mercury is "ships of discovery or scientific expeditions". By the nature of world history, there is a preponderance of Western ship names. For example, we find Adventure, Discovery, Endeavour, and Resolution – all four ships from Captain Cook's 18th-century voyages to the Southern Ocean and Pacific.

Personally, I am content that these were primarily journeys of scientific discovery rather than of conquest or colonisation. Cook's first voyage was undertaken to observe a rare transit of Venus, and his second voyage reached further south than ever before.

Endeavour Rupes, the shadowed escarpment in the middle of a 400km wide view of Mercury. Credit: NASA/JHUAPL/CIW

That said, it would be nice to redress the balance. In connection with a European planetary mapping project, one of my Ph.D. students and I hope to get at least one of Mercury's as yet unnamed Rupes named after a canoe in which the Maoris arrived in New Zealand.

Ultimately, space exploration is for all of humanity.

Explore further: Mysterious red spots on Mercury get names – but what are they?

Related Stories

Mars name-a-crater scheme runs into trouble

March 11, 2014

The world's paramount astronomical authority on Tuesday slapped down a bid to hawk the names of Mars' craters, saying the Red Planet's monickers are not up for sale.

Concerns and considerations with the naming of Mars craters

March 11, 2014

Recently initiatives that capitalise on the public's interest in space and astronomy have proliferated, some putting a price tag on naming space objects and their features, such as Mars craters. The International Astronomical ...

Pluto features given first official names

September 7, 2017

The Working Group for Planetary System Nomenclature of the International Astronomical Union has officially approved the naming of 14 features on the surface of Pluto. These are the first geological features on the planet ...

Recommended for you

Matter waves and quantum splinters

March 25, 2019

Physicists in the United States, Austria and Brazil have shown that shaking ultracold Bose-Einstein condensates (BECs) can cause them to either divide into uniform segments or shatter into unpredictable splinters, depending ...

How tree diversity regulates invading forest pests

March 25, 2019

A national-scale study of U.S. forests found strong relationships between the diversity of native tree species and the number of nonnative pests that pose economic and ecological threats to the nation's forests.

Study suggests trees are crucial to the future of our cities

March 25, 2019

The shade of a single tree can provide welcome relief from the hot summer sun. But when that single tree is part of a small forest, it creates a profound cooling effect. According to a study published today in the Proceedings ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jan 03, 2019
Here is an attempt to trace the etymologies of those smaller craters on Mars named for cities and towns. This document is and always will be incomplete but help is solicited from people who may have knowledge about these names.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.