Evolution of the Moon: the 1974 model

The interpretive evolution of the Moon can be divided now into seven major stages beginning sometime near the end of the formation of the solar system. These stages and their approximate durations are as follows: 1. The Beginning - 4.6 billion years ago. 2. The Melted Shell-4.6-4.4 billion years ago. 3. The Cratered Highlands -4.4-4.1 billion years ago. 4. The Large Basins-4.1-3.9 billion years ago. 5. The Light-Coloured Plains-3.9-3.8 billion years ago 6. The Basaltic Maria -3.8-3.0 billion years ago. 7. The Quiet Crust-3.0 billion years ago to the present. The Apollo and Luna explorations that permit the study of these stages of evolution have each contributed in progressive and significant ways. Through them the early differentiation of the Earth, the nature of the Earth's protocrust, the influence of the formation of large impact basins in that crust, the effects of early partial melting of the protomantle and possibly the earliest stages of the breakup of the protocrust into continents and ocean basins can now be looked at with new insight. (Auth.)