NEEP602 Course Notes (Fall 1996)
Resources from Space
TABLE 2. Apollo model for the evolution of the Moon
Stage Age (eons)
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Pre-Nectarian
Beginning 4.55
Contemporaneous with Earth
Early cold accretion below about 480 km
Magma ocean 4.55-4.4(?)
Accretionary melting above about 480 km
Volatile depletion
Differentiation nf 60 km thick crust
Separation of urKREEP liquid
Separation of iron-sulfur liquid
Cratered highlands 4.4(?)-4.2(?)
Crater saturation to >50 km diameter
Crustal brecciation to >25 km
Old large basins/crustal strengthening 4.2(?)-3.9
Formation of >29 basins
Crustal thinning and thickening
Impact materials broadly distributed
Isostatic adjustment
UrKREEP liquids moved into lower crust
Strengthening of the crust
Nectarian and Lower Imbrium
Young large basins 3.9-3.8
Formation of 14 basins
Mascons and mass deficiencies sustained
Impact materials broadly distributed
Upper Imbrium
Basaltic maria 3.8-3.0(?)
Downwardly phased mantle partial melting
Early eruptions of crustal debris
Basaltic intrusions and extrusions
Basin related extensional faulting
Late mafic pyroclastic eruptions
Eratosthenian and Copernican
Mature surface 3.0(?)-
Rayed crater formation
Surface regolith formation
Bright swirl alteration of large areas
Declining meteor impact frequency
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