the early heavy bombardment
Stato: Niuafo'ou Anno: 1989 Notizie: Between 1989 and 1993 Niuafo'ou (Tin Can Island) issued a series of stamps depicting phases in the history of the Earth. Among these is a stamp showing the early heavy bombardment of Earth's crust by cosmic debris. The Earth and the other terrestrial planets (Mercury, Venus, Earth, and Mars) -- as well as Earth's moon -- experienced a major era of bombardment from 4.5 to about 3.9 billion years ago called the early heavy bombardment . Large impacts occurred frequently during this period. After this the cratering rate declined exponentially. Later impacts (after 3.3 billion years ago) occurred much less frequently and the impactors were smaller. |
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