Macleer is a lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

-flooded crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 on the northwest part of the Mare Tranquillitatis

Mare Tranquillitatis

Mare Tranquillitatis is a lunar mare that sits within the Tranquillitatis basin on the Moon. The mare material within the basin consists of basalt formed in the intermediate to young age group of the Upper Imbrian epoch. The surrounding mountains are thought to be of the Lower Imbrian epoch, but...

, a lunar mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

 in the eastern half of the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

. The crater is located to the southeast of the slightly larger Ross

Ross (lunar crater)

Ross is a lunar crater that is located in the northwest part of the Mare Tranquillitatis. It lies south-southwest of the crater Plinius, and northwest of the lava-flooded Maclear....

. To the southwest of Maclear is Sosigenes

Sosigenes (crater)

Sosigenes is a lunar impact crater on the west edge of Mare Tranquillitatis. It lies to the east of the large walled plain Julius Caesar. The crater rim has a high albedo, making it relatively bright. It has a small central rise at the mid-point of the floor....

, while farther to the south-southeast is Arago

Arago (lunar crater)

Arago is a lunar impact crater located in the western part of the Mare Tranquillitatis. To the southwest lies the crater Manners, and beyond are Dionysius and the Ritter–Sabine crater pair. To the southeast is the large Lamont formation that has been submerged by the mare.The rim of Arago has a...

.

With most of its interior submerged in deposits of basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic lava, all that remains of this crater is a narrow rim projecting above the surrounding mare. The rim is not quite circular, having a flat outward bulge along the western side. But the rim is relatively uniform in width and is not significantly eroded.

The crater rim lies at the southern terminus of a rille

Rille

Rille is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length...

 belonging to a system that runs along the western edges of Mare Tranquillitatis. The rille system to the north of the crater is designated Rimae Maclear, while the rilles to the south-southwest are named Rimae Sosigenes. The Rimae Maclear stretches for about 100 kilometers, reaching Al-Bakri

Al-Bakri (crater)

Al-Bakri is a small lunar crater on the northwest edge of Mare Tranquillitatis. It is just south of the eastern arm of the Montes Haemus that borders the Mare Serenitatis to the north. To the east-northeast is the prominent crater Plinius. South of the crater are the rilles of the Rimae...

 to the north along the edge of the mare.

It is named after Sir Thomas Macleer, Her Majesty's astronomer

Astronomer

An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

 at the Royal Observatory, Cape of Good Hope (Cape Town

Cape Town

Cape Town is the second-most populous city in South Africa, and the provincial capital and primate city of the Western Cape. As the seat of the National Parliament, it is also the legislative capital of the country. It forms part of the City of Cape Town metropolitan municipality...

, South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

), from 1833 to 1870.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Maclear.

Macleer	Latitude	Longitude	Diameter
A	11.3° N	18.0° E	5 km