Birkeland (lunar crater)
Lunar impact crater
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Birkeland is a lunar impact crater that lies in the southern hemisphere on the far side of the Moon.[3] This crater is attached to the central waist of the oddly shaped Van de Graaff crater formation,[4] and may partly account for that crater's figure-8 shape. To the southeast is the large walled plain named Leibnitz. Birkeland is located within the South Pole-Aitken basin (SPA).[5]
Lunar Orbiter 2 image | |
| Coordinates | 30.2°S 173.9°W |
|---|---|
| Diameter | 81.64 km (50.73 mi)[1] |
| Depth | Unknown |
| Colongitude | 187° at sunrise |
| Formation | Eratosthenian[2] |
| Eponym | O. Kristian Birkeland |
This formation dates to the Eratosthenian epoch of the lunar geologic timescale.[2] It has not been significantly eroded, and the outer rim is well-defined with a well-terraced inner walls around much of the interior. The rim has a slight inward bulge along the north where it is attached to the Van de Graaff formation.[6]: 104
The interior floor is relatively level, except in the southeast where there is some rough terrain. There is a central peak formation at the midpoint.[5] The spectra of this orthopyroxene-rich central peak fits a olivine-bearing norite mineralogy, which originated from a depth of 8.2 to 12.9 km.[7] The crater has a strong thorium anomaly, which is consistent with excavated material from the differentiated melt sheet created by the SPA impact.[8]
This crater is named after Norwegian physicist O. Kristian Birkeland (1867–1917).[9] Its designation was formally adopted by the International Astronomical Union in 1970.[1]