Scale: 1 pixel = 2 km. 5-degree grid;
Mercator Projection, Projection Center 00NS 145WE; Map center 00NS 145W
|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
Korolev (named for Sergei Korlolev, mastermind of the Soviet space program) and Hertzsprung (named for Ejnar Hertzsprung, Danish astronomer and co-inventer of the Hertzsprung Russell Diagram, a fundamental tool for investigating stellar evolution) are plenty big enough to be sizable maria, but are completely lacking in mare lavas. Korolev is recognizable on the geologic map but Hertzsprung is entirely invisible. It's morphologically evident but mantled by Mare Orientale and other younger deposits.
Created 11 April 2014, Last Update
12 March 2015
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