Consider, for example, our moon's history, as inferred from data collected during the Apollo missions and summarized by Coumbia University geologist W. Ian Ridley: The moon's crust rigidified more than 4 billion years ago. By 3.9 billion years ago, the greatest period of meteoritic bombardment had ended, the mare basins had been excavated, and the major craters formed. Between 3.1 and 3.8 billion years ago, radioactivily generated heat produced the basaltic lava that filled the mare basins. Then the generation of new heat failed to match its loss at the lunar surface and the crust rigidified again: by 3.1 billion years ago, the crust became too thick to permit the ascent of any more basalt, and activity at the lunar surface essentially ended. Since then, nothing much has happened beyond the very occasional impact of a large meteorite and the constant influx of very small ones.

Ever since Darwin, p 194.