Scale: 1 pixel = approximately 4.7 km. 10-degree grid; Lambert Azimuthal Equal Area Projection, Center 55S 160W
|Copernican: Beginning with the formation of the
bright crater Copernicus, about 1.1 Ga. Formation of bright ray
Eratosthenian: Begins with the formation of the crater Eratosthenes. Fresh but non-rayed craters and late mare eruptions. 1.1 to 3.1 Ga.
Imbrian: Begins with the formation of the Imbrium Basin. Includes most mare eruptions. 3.1 to 3.8 Ga.
Nectarian: Begins with the formation of the Nectaris Basin, and includes most of the major impact basin events. 3.8 to 3.9 Ga.
pre-Nectarian: Before 3.9 Ga
Despite being the largest and deepest impact basin on the Moon, as well as the oldest (pre-Nectarian), the South Pole-Aitken Basin is all but unrecognizable on the geologic map since it is overprinted by younger craters. The highlands to the north include the highest point on the Moon and may be impact deposits from the formation of this basin. The asymmetry of the highlands has been suggested as indicating an oblique impact. The floor of one of the craters within the basin also includes the lowest point on the Moon.
The odd swirling pattern around the south pole on the shaded relief maps is an artifact of the computer shading process. Illumination is from the northeast (typical on shaded relief maps) but directions are defined in terms of local coordinates, so the illumination direction changes rapidly close to the pole.
Created 11 April 2014, Last Update
12 March 2015
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