NEEP602 Course Notes (Fall 1996)
Resources from Space

TABLE 2. Apollo model for the evolution of the Moon

               Stage                           Age (eons)
 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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