Black (crater)

Black crater is a relatively small, bowl-shaped impact crater with a diameter of about 18 kilometers. It lies in the western part of the Oceanus Procellarum, at selenographic coordinates 9.2°N, 9.2°W. The crater has a somewhat irregular rim that is slightly worn, and its interior is relatively flat, with a small central peak that is not prominent. The crater's floor has a lower albedo than the surrounding mare, giving it a dark appearance that is characteristic of craters that have been filled with basaltic lava or have dark-haloed ejecta. This dark halo is particularly noticeable in the western portion of the crater, and it is thought to be due to the presence of pyroclastic deposits or dark mare material that was excavated during the impact.¹

Black crater is part of a chain of craters that includes Krieger to the northwest and Van Biesbroeck to the southwest. This alignment is not random; it is thought to be the result of a single impact event that broke up a body before it struck the Moon, creating a series of craters along a line. The region is also notable for the presence of dark mantle deposits, which are volcanic ash or pyroclastic materials that cover the surface. These deposits are associated with the eruption of basaltic magma that occurred in the Oceanus Procellarum region. The dark halo around Black crater is likely a result of the impact excavating these dark materials from beneath the lighter regolith.²

Black crater was first observed in detail by the Lunar Orbiter missions in the 1960s, which provided high-resolution images of the lunar surface. Later, the Apollo missions, particularly Apollo 15 and 17, obtained further imagery and data from orbit. The crater has been a target for studies of lunar volcanism and impact processes. In 2010, the Lunar Reconnaissance Orbiter (LRO) captured high-resolution images that revealed the crater's morphology in unprecedented detail, showing a well-preserved rim and a relatively smooth floor.³

One lesser-known aspect of Black crater is its association with the 'dark halo' phenomenon, which is relatively rare among lunar craters. Dark-haloed craters are often interpreted as sites of explosive volcanic eruptions, but Black's dark halo is more likely due to the excavation of dark basaltic material from beneath a lighter surface layer. Another notable detail is that Black crater is part of a crater triplet with Krieger and Van Biesbroeck, which may have formed from a single oblique impact that fragmented the impactor. Additionally, the crater's name was officially adopted by the International Astronomical Union in 1935, but it was not until the 1960s that detailed mapping revealed its true nature. Some amateur astronomers have reported observing the dark halo visually with large telescopes, but it is a subtle feature that requires good seeing conditions.⁴

Albedo

The reflectivity of a surface; a lower albedo means darker appearance.

Basaltic lava

Dark, iron-rich volcanic rock that forms the lunar maria.

Dark-haloed crater

A crater surrounded by a dark deposit, often due to volcanic ash or dark ejecta.

Oceanus Procellarum

A large lunar mare on the western edge of the Moon's near side.

Pyroclastic deposits

Volcanic material ejected during explosive eruptions.

Regolith

The layer of loose, fragmented material covering solid rock on the Moon.