NEEP602 Course Notes (Fall 1996)
Resources from Space

TABLE 2. Apollo model for the evolution of the Moon



               Stage                           Age (eons)
------------------------------------------------------------
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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