You’ll no doubt have heard of the Sea of Tranquility, the lunar “sea” that was used as the landing site for the Apollo 11 lunar module, the Eagle, on July 20, 1969. You might also have heard of some of the other seas on the Moon, like the Sea of Vapors, the Sea of Clouds, and the Ocean of Storms. But what about the Sea of Cleverness, the Sea of Crises, and the Sea of Fecundity? Or the Lake of Forgetfulness, the Lake of Hatred, and the Marsh of Decay? All of these are genuine landmarks and landscape features on the surface of the Moon, whose names are now accepted by the astronomical community. 

But it doesn’t end there. As more of the solar system has been explored and imaged, all kinds of geographical features have been mapped on many of our planets and satellites from Mercury to Neptune (sorry, Pluto). The official names of all these features are governed and approved by an organization known as the International Astronomical Union, or the IAU, which has set out a strict series of rules, customs and guidelines dictating what these features—12 of which are listed here—must be named after.

1. ALCOTT

Because Venus is named after one of the most important goddesses in Roman mythology, almost all of the planet’s geographical features have likewise been named for renowned women, deities, and other famous female figures. (Canyon-like formations called valles, if longer than 400 km, are named after names for Venus in other languages, which are not necessarily female.) Alcott is a 40 mile-wide crater in the planet’s southern hemisphere named after Little Women author Louisa May Alcott. The novelists Jane Austen, Anaïs Nin, Ayn Rand, Dorothy L. Sayers, Harriet Beecher Stowe, and Edith Wharton all also have Venusian craters named after them, as do Billie Holiday and Edith Piaf, the poets Elizabeth Browning and Emily Dickinson, the actress Sarah Bernhardt, the artists Frida Kahlo and Georgia O’Keeffe, waxwork maker Madame Tussaud, and Hua Mulan, the famous Chinese warrior.

2. BEAGLE

The rocky, crater-strewn surface of Mercury is marked by a number of vast escarpments and precipices known in astronomical terms as rupis (the Latin word for “cliffs”). All of Mercury’s rupis have been given the names of famous exploratory ships, including Beagle, discovered in 2008, which takes its name from Charles Darwin’s research ship the HMS Beagle. Elsewhere on Mercury you can find rupis named Adventure, Discovery, Resolution, and Endeavour (all named after Captain Cook’s ships), Santa Maria (named for one of Christopher Columbus’s ships), and Fram (named after the ship used by Norwegian explorer Roald Amundsen on his expedition to the South Pole in 1910). 

3. BEETHOVEN

All of the craters on Mercury are named after deceased artists, writers, composers, musicians, or similarly artistic and creative types, who, according to IAU rules, have to have been dead for at least three years, and to have been recognized as internationally significant within their particular field for at least half a century. Beethoven, at around 400 miles wide, is one of the largest of all Mercury’s craters and one of the largest in the entire solar system. Others include Bach, Brahms, Chopin, Debussy, Haydn, Mozart, Prokofiev, Stravinsky, Vivaldi, and Wagner

4. CLACKMANNAN

Clackmannan is the name of a small town in the Scottish lowlands around 35 miles outside of Edinburgh, but it is also the name of an impact crater on Mathilde, a medium-sized asteroid orbiting the Sun in the main asteroid belt between Mars and Jupiter. Mathilde is dark-colored and carbonaceous, so all of its surface features have been named after places and regions on Earth known for coal production—and as what was once one of Scotland’s foremost coalmining towns, Clackmannan was honored by the IAU in 2000.

5. GALAHAD

Mimas is the seventh largest moon of Saturn, but with a diameter of just under 250 miles, it is still just one-eighth the size of our Moon—laid out flat, its entire surface would only cover an area about the size of Spain. Geographical features on Mimas are traditionally named after characters from the legend of King Arthur, and amongst the 35 officially named craters on the moon are Bedivere, Galahad, Gwynevere, Launcelot, Merlin, Mordred, and Percivale.

6. McAULIFFE

As of 2015, the names of more than 1500 craters on the surface of our Moon have been approved by the IAU, the vast majority of which commemorate scientists, astronomers, and explorers who have made a particular contribution to their respective fields. Around a dozen craters, however, have been reserved for astronauts and cosmonauts who lost their lives in the pursuit of space exploration—including McAuliffe, a 11 mile-wide impact crater on the far side of the Moon named after Christa McAuliffe, the schoolteacher and civilian astronaut who was one of seven crewmembers tragically killed in the Challenger disaster in 1986. All six of her fellow crewmembers are also commemorated in the names of lunar craters, as are the crew of the ill-fated Apollo 1 mission, who died in a fire at Cape Canaveral in 1967, and cosmonauts from Soyuz 1 and 11 who were killed during re-entry accidents in 1967 and '71, respectively.

7. THE MISTY MOUNTAINS

All of the mountains and mountain ranges on Titan, the largest moon of Saturn, are named after mountains in Middle Earth, the fictional world created by Lord of the Rings author JRR Tolkien. As well as the Misty Mountains (or the Misty Montes, to give them their astronomical name), Titan also has a real-life 4750 foot high Mount Doom.

8. NAPLES

How far is it to Naples? About 1.6 billion miles. That’s because Naples is the name of a sulcus—a long geological groove or chasm—on the surface of Miranda, the smallest and innermost of the five main moons of Uranus. Traditionally all of Uranus’s moons are named after characters from Shakespeare or Alexander Pope, and in turn many of their geographical features take their names from the settings and characters of Shakespeare’s plays. The Naples sulcus is named after the Italian city that features prominently in The Tempest, but there’s also Inverness (a corona, or oval-shaped landmass, named after the location of Macbeth’s castle), Verona (a ridge of cliffs named after the setting of Romeo & Juliet), and Syracuse (another sulcus named after the home of the twins in The Comedy of Errors).

9. OAHU

So if it’s over a billion miles to Naples, how far is it to Oahu? Well, not quite as far—only about 750 million miles. Oahu is a facula (a glowing bright spot) on the surface of Titan. All of Titan’s facula are named after islands here on Earth that aren’t independent countries in their own right—some of the others so far named include Crete, Elba, and Mindanao. 

10. PROMETHEUS

Io, the third largest of Jupiter’s moons, is the most geologically and volcanically active body in the entire solar system. Despite being less than a tenth the size of the Earth (4.5 USAs would be enough to cover its entire surface) there are thought to be more than 400 active volcanoes strewn across Io—over twice as many as in the entire U.S. Because of all of this extreme volcanic activity, many of the geographic landforms and features on Io have been named after gods and goddesses associated with fire, thunderstorms, and the Sun. Named for the Greek Titan who stole fire from the gods as a gifts for humanity, Prometheus—an enormous 17 mile-long volcanic pit that has been erupting continuously since it was first discovered by the Voyager space probe in 1979—is just one example.

11. SACAJAWEA

As another of the solar system’s most volcanic bodies, Venus’s surface is home to a number of paterae, including Sacajawea, a vast 140 mile-wide depression thought to have been formed by the collapse of a huge volcano. Named after a type of saucer-like drinking vessel from Ancient Rome, paterae are large, shallow indentations on the surfaces of planets and moons that are usually formed by volcanic activity. 

12. SWIFT

In Gulliver’s Travels, Jonathan Swift wrote how the Laputans, the enlightened inhabitants of the flying island of Laputa, had discovered “two lesser stars, or satellites, which revolve around Mars.” Swift’s book was published in 1726, but in reality the two real-life moons of Mars—Phobos and Deimos—would not be discovered for another 151 years. So in honor of Swift’s remarkably accurate prediction, a crater on Deimos was named Swift when the moon was first accurately mapped in 1973. Another nearby crater is named Voltaire, after the French writer who also predicted the existence of a pair of Martian moons long before they were discovered.