Penitentes, erosional snow and ice features. These are earthly ones, but there are similar features in Tartarus Dorsa on Pluto.

New Horizons was nearing Pluto in 2015 and the mission team would need names for the surface features they discovered. So they appealed to the public. The names would be informal ones, but they hoped the International Astronomical Union (IAU) would make them official. Here's the official list so far.

International Astronomical Union
The International Astronomical Union (IAU) names heavenly objects and their surface features. Making use of the New Horizons suggestions, the working group published a list of 14 names in August 2017. The following year two more names were added, and they also produced a list for Pluto's moon Charon.

Six themes were used in choosing the names, many inspired by Pluto's own name, that of the Roman god of the underworld. They included mythological figures and places related to the underworld, explorers, pioneering space missions, and scientists associated with Pluto.

Surface features
A regio is a large area that's in some way distinct from its surroundings. Tombaugh Regio is the prominent light-colored heart that delighted the public when the first images arrived from New Horizons. It's about 1,590 km (990 mi) across, and was named for Clyde Tombaugh who discovered Pluto in 1930.

A planitia is a low plain. Sputnik Planitia is a large frozen nitrogen ice sheet forming the western lobe of the Tombaugh Regio “heart”. Sputnik, launched in 1957 by the Soviet Union, was the first artificial satellite to orbit the Earth.

Sputnik Planitia is bordered by several mountain ranges described as “chaotic” and “blocky”. The two most prominent ones celebrate the conquerors of Everest: Tenzing Norgay, the Indian-Nepali Sherpa, and Sir Edmund Hillary, New Zealand mountaineer. The mountains are called montes, and you can see them on this map of informal names.

Tenzing Montes (on the map as Norgay Montes) is 6.2 km (20,000 ft) from base to peak. It dwarfs the other Plutonian mountains and outdoes Everest's base to peak height of around 4.7 km (15,000 ft). Hillary Montes is just over half the height of Tenzing Montes, 3.5 km (11,000 ft).

Al-Idrisi Montes honors the noted Arab geographer nicknamed Ash-Sharif al-Idrisi (1100-1165). His chief work is delightfully titled “The Pleasure Excursion of One Who Is Eager to Traverse the Regions of the World”, one of the most famous works of medieval geography.

Baret Montes was a name approved in 2018. A Frenchwoman Jeanne Baret (1740-1807) is recognized as the first woman to circumnavigate the globe. She was an accomplished botanist. Also very adventurous, Baret made most of her around the world trip disguised as a man on the expedition of explorer Louis-Antoine de Bougainville.

A Fossa (plural: fossae) is a long narrow depression. Those on Pluto are named after figures associated with underworld myths.

Djanggawul Fossae is a network of fossae. The Djanggawuls are three ancestral beings in indigenous Australian mythology who created the Australian landscape and flora. Although mainly associated with creation and fertility, they came to Earth from Beralku, the island of the dead.

Sleipnir Fossa is Odin's powerful eight-legged horse that carried the god throughout the worlds of the world tree Yggdrasil. One of their most famous journeys was to the underworld, known as Hel in Norse mythology.

It wasn't Virgil's poetry that inspired the name Virgil Fossa, but in Dante's work The Divine Comedy, the ancient Roman poet was his fictional guide through hell and purgatory.

A cavus is an irregular hollow with steep sides, usually — but not always — found in groups. Adlivun Cavus is a deep depression named for the underworld in Inuit mythology. Hekla Cavus is a 2018 addition to the list. Hekla, one of Iceland's most active volcanos, was known to medieval people as the “Gateway to Hell”.

A dorsum [plural: dorsa] is a mountainous ridge, so it's slightly odd that Tartarus Dorsa has the name of the deepest abyss of the Greek underworld. Yet as a place of torment for the very wicked, perhaps the name works. The dorsa contains penitentes, erosional snow and ice features that echo the tall, narrow, white pointed hats worn in Holy Week Processions of Penance in Spain. They're like the earthly ones shown in the header image.

Terrae are extensive landmasses. Two have been named after space probes, Hayabusa Terra and Voyager Terra. Hayabusa is the Japanese spacecraft that in 2003-2010 carried out the first asteroid sample return, landing briefly on asteroid 25143 Itokawa. NASA's two Voyager missions, launched in 1977, between them visited the four giant planets. They are both now in interstellar space.

Elliot crater was named for James Elliot (1943-2011), an astronomer who pioneered the use of stellar occultations to study the Solar System. One such occultation led to the first detection of Pluto's thin atmosphere.

Finally, amid the features named for gods and heroes, scientists and engineers, and myths and explorers is Burney Crater. Venetia Burney (1918-2009) was the 11-year-old English schoolgirl who suggested the name Pluto for Tombaugh's discovery. The crater is actually a basin some 250 km (155 mi) across that contains a number of smaller craters. Most of the craters in this image are in the basin.