Geological Chronicle
Birkeland is an impact crater in the southern hemisphere on the far side of the Moon, located within the South Pole-Aitken basin. The crater attaches to the central waist of the oddly shaped Van de Graaff crater formation, and its rim has a slight inward bulge along the north where the two features meet. Birkeland may partly account for Van de Graaff's figure-8 shape, while the large walled plain Leibnitz lies to the southeast.
The formation dates to the Eratosthenian epoch of the lunar geologic timescale and has not been significantly eroded. Its outer rim is well-defined, and well-terraced inner walls line much of the interior. The floor is relatively level, except for rough terrain in the southeast, with a central peak formation standing at the midpoint.
Spectra of the orthopyroxene-rich central peak fit an olivine-bearing norite mineralogy that originated from an estimated depth of 8.2 to 12.9 km. Birkeland also has a strong thorium anomaly, consistent with excavated material from the differentiated melt sheet created by the South Pole-Aitken basin impact.