20 things to see on the Moon: An observers guide to lunar names – Astronomy Magazine

All photos by Robert Reeves

For over 400 years, legions of lunar cartographers have been surveying the surface of the Moon first by telescope and then by spacecraft charting and naming its features.

The resulting lunar map is constantly evolving. Over time, new names are added while existing names are dropped or changed after research shows a feature to be of a different geological type. The International Astronomical Union (IAU) establishes guidelines for lunar names; their approval is required to make a name official. These efforts keep scientific order in how we identify features and navigate the face of the Moon.

But our relationship with the Moon is not all science and regulated order. It is human nature to create endearments for the things we love. Deep-sky observers bestow unofficial nicknames to many, like the Lagoon (M8), Rosette (NGC 22379/44), and California (NGC 1499) nebulae. Luna is no exception; it too has its share of fanciful unofficial names for its features.

Human whimsy often trumps science in these names, such as the Cobra Head at the volcanic source that once fed flowing lava into Schrters Valley. During the Apollo expeditions, many astronauts made their mark on the Moon by giving features unofficial names, such as Jim Lovells famous Mount Marilyn, which he named after his wife during Apollo 8. While some of these popular lunar names are eventually rubber-stamped by the IAU (including Mount Marilyn in 2017), others do not appear on a map, but persist by general acceptance.

The selection of unofficial names presented here include some modestly proposed by the author. Whether they stick in lunar lexicon depends on the whims of Moon lovers everywhere.

Lunar nicknames bring life and familiarity to a stark and unforgiving landscape that is nonetheless appealing because of its alien strangeness. For the avid astronomer, the names here should become as familiar as the terms of endearment that we apply to the gems of the Milky Way and beyond.

Named by: Robert Reeves

Official name: Cleomedes, Burckhardt, Geminus, and Messala craters

Size: 81 miles (131 km), 34 miles (54 km), 51 miles (82 km), 76 miles (122 km)

Coordinates: centered at 33.5 N, 57.8 E

Feature named after: Appearance of sequential steppingstones

The linear string of four large craters extending north from Mare Crisium (at far lower right in this image) is reminiscent of steppingstones leading off to an adventuresome place. Each step is a leap through time, as none of these craters are the same age. The southernmost is flat-floored Cleomedes, an 81-mile-wide (131 kilometers) Nectarian-epoch crater that dates back 3.85 billion to 3.95 billion years ago. The smaller and slightly younger Imbrian-epoch crater Burckhardt follows. Farther north the sharper form of Geminus is even younger, dating to the Eratosthenian epoch. The final steppingstone, massive, ruined, pre-Nectarian-epoch Messala, is the oldest.

Named by: Unknown

Official name: Furnerius A, Stevinus A

Size: 7 miles (11 km), 5 miles (8 km)

Coordinates: 33.0 S, 54.7 E

Feature named after: Appearance of oncoming car headlights

Satellite craters usually do not draw the casual observers attention, but the brilliant, similar-sized Furnerius A and Stevinus A are an exception. Both young Copernican-epoch craters display disproportionately bright ray systems. The brilliant craters bracket the 45-mile-wide (72 km) Stevinus on the Moons southeast quadrant, creating the illusion of approaching car headlights.

Named by: Robert Reeves

Official name: Meton, Meton C, D, E

Size: 124 miles (200 km)

Coordinates: 72.6 N, 20.0 E

Feature named after: Appearance of a four-leaf clover

The merged forms of craters Meton C, D, and E overlaying Meton Crater on the northern polar landscape create a four-leaf clover shape representing a lunar good-luck charm. The interiors and rims of all four pre-Nectarian-epoch craters were buried by the wave of ejecta thrown from the Imbrium Basin impact 3.85 billion years ago, forming a common floor lying 5,000 feet (1,500 meters) below the surrounding territory.

Named by: Unknown

Official name: Rupes Liebig

Size: 90 miles (145 km)

Coordinates: 45.9 W, 25.1 S

Feature named after: Scarp with the same name

Lengthy Rupes Liebig arcs along the western shore of Mare Humorum and descends 2,300 feet (700 m) to the mare floor. The 6-mile-wide (9 km), 5,600-foot-deep (1,700 m) crater Liebig F lies atop the scarp and inspires the unofficial designation of the Liebig Wall.

Named by: Robert Reeves

Official name: None

Size: 6 miles (10 km)

Coordinates: 22.0 N, 55.5 E

Feature named after: Resembles a waterfall cascading down a mountainside

A bright splash of light-colored material ejected from a 0.8-mile-wide (1.3 km) craterlet on a mountainside on the northern rim of Mare Crisium looks almost as if it were a waterfall cascading down to the plain below. This bright, white spot can be found by following the northward arc of the craters Picard, Pierce, and Swift on the western side of Crisium. The spot has been reported to be a transient lunar event, as its reflectivity is variable and dependent on the Sun illumination angle, as seen in a comparison of these two images. The physical feature, however, is permanent. While the spot has no official name, Rik Hill, now retired from the University of Arizona, published an analysis of it thus, it is referred to as Hills Waterfall.

Named by: Robert Reeves

Official name: Lamont

Size: 52 miles (83 km)

Coordinates: 5.1 N, 23.3 E

Feature named after: Spiderlike appearance

First charted as a ghost crater on western Mare Tranquillitatis, Lamont is now regarded as a small ghost basin due to the 84-mile-wide (135 km) outer ring surrounding it. Lamont contains a spiderlike structure consisting of a system of lengthy radial wrinkle ridges that rise between 330 and 1,000 feet (100 and 300 m) above their surroundings. These form the legs of the spider.

Named by: Robert Reeves

Size: 44 miles (70 km)

Coordinates: 50.2 N, 20.1 E

Feature named after: Appearance of the letter S under sunset illumination

The apparition of the letter S appears for several hours at sundown on the eastern flank of Aristoteles Crater. The S is a combination of the northern rim of 19-mile-wide (30 km) Mitchell Crater, protruding from under Aristoteles eastern rim, and the swirl of topography north of Mitchell.

Named by: Unknown

Official name: Linn A 1

Size: 22 miles (35 km)

Coordinates: 30.4 N, 10.1 E

Feature named after: Appearance of a Valentines heart

The volcanic dome Linn A 1, just right of center in this image, rises 1,000 feet (300 m) above western Mare Serenitatis and is topped by half a dozen smaller volcanic domes, some capped with a small caldera. The rounded pancake-shaped dome resembles a classic Valentines heart.

Named by: Robert Reeves

Official name: None

Size: 93 miles (150 km)

Coordinates: 10.5 N, 6.8 E

Feature named after: Heart-shaped appearance

Some 370 miles (600 km) south of Valentine Dome lies another heart-shaped feature: the dark volcanic-ash-dusted mountains north of Rima Hyginus on Mare Vaporum, which reach 3,300 feet (1,000 m) in elevation. The mountains have no official name, but the overall appearance of the rugged region prompts the unofficial designation of the Heart of the Moon.

Named by: Unknown

Official name: None

Size: 68 miles (110 km)

Coordinates: 25.4 S, 1.0 E

Feature named after: Appearance of the letter X

As the First Quarter sunrise terminator crosses the merged rims of the adjacent craters Purbach, La Caille, and Blanchinus, they protrude in an X-shaped pattern that catches the first rays of sunrise and remains visible for about four hours.

Named by: Unknown

Official name: Hills: none; Tadpole: Reiner Gamma

Size: Hills: 171 miles (275 km); Tadpole: 124 miles (200 km)

Coordinates: Hills: 12.6 N, 53.9 W; Tadpole: 7.6 N, 58.6 W

Feature named after: Hills: nearby crater Marius; Tadpole: resemblance to a frog tadpole

The Marius Hills are the unofficial name for the 262 individual mounds on a 27,000-square-mile (70,000 square km) region of Oceanus Procellarum west of the crater Marius. Although casually called hills, the features are volcanic domes and cinder cones. Reiner Gamma, located west of the Marius Hills and affectionately known as the Tadpole, gets its nickname from its resemblance to this stage in a frogs life cycle. This feature possesses no vertical relief, does not cast a shadow, and is officially classified as an albedo feature.

Named by: Straight Wall: Birt and Lee (1865); Ancient Thebit: Chuck Wood

Official name: Straight Wall: Rupes Recta; Ancient Thebit: none

Size: Straight Wall: 72 miles (116 km); Ancient Thebit: 105 miles (170 km)

Coordinates: 21.7 S, 7.7 W

Feature named after: Straight Wall: Linear appearance; Ancient Thebit: Proximity to Thebit Crater

Rupes Recta is a lengthy linear feature known by the beloved name of Straight Wall (a rough translation of its Latin name). It is also known as Huygens Sword in honor of 17th-century astronomer Christiaan Huygens, who studied the feature. The curved exposed crater rim at the southern end of Rupes Recta is also known as the Stags Horn. Straight Wall lies in an unnamed ghost crater marked by a horseshoe-shaped bay east of the Wall and the circular wrinkle ridges west of it. This crater was unofficially designated Ancient Thebit by Chuck Wood after the nearby, younger Thebit Crater.

Named by: Chuck Wood

Official name: None

Size: 13 miles (21 km)

Coordinates: 47.8 N, 0.3 W

Feature named after: Two mountains guarding a narrow gorge

The mouth at the western end of the Alpine Valley (Vallis Alpes) slashing through the lunar Alps (Montes Alpes) funnels from 13 miles (21 km) across down to a gorge just 660 feet (200 m) wide at the valleys entrance. The narrow channel is bounded by a northern massif that rises 6,500 feet (2,000 m), while the southern massif rises 8,200 feet (2,500 m) above the plains of Mare Imbrium. Chuck Wood unofficially named the twin mountains the Guardians.

Named by: Unknown

Official name: Tycho rays

Size: 447 miles (720 km)

Coordinates: 32.8 S, 19.5 W

Feature named after: Parallel placement, akin to railroad tracks

Tycho Craters two prominent northwestern ray streamers do not diverge from a point within Tycho, and each ray is tangential to the craters rim. This unusual parallel nature prompted the unofficial designation of the Railroad Tracks.

Named by: Robert Reeves

Official name: Flamsteed P, Wichmann R

Size: 62 miles (100 km), 40 miles (64 km)

Coordinates: 4.5 S, 40.7 W

Feature named after: Ghost crater locations

The Moons large basins were once dotted with craters, before volcanic flooding flooded many of them and created the maria. Some remain visible as ghost craters with their crowns protruding above the mare basalt. Those on southern Oceanus Procellarum are collectively known as the Ghosts of Procellarum.

Named by: Unknown

Official name: None

Size: 44 miles (70 km)

Coordinates: 16.8 S, 31.5 W

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20 things to see on the Moon: An observers guide to lunar names - Astronomy Magazine