Mare formation on the Moon

Mare formation on the Moon

Fig. 5.28 . Disintegrating and vaporizing as it strikes, a meteorite blasts a huge impact basin out of the lunar surface (left), while the associated shock waves create fractures in the rock beneath the basin. The blast hurls up mountain ranges around the basin (middle), and the underlying rock adjusts to the loss of mass above it by rebounding upward. The uplifted mantle causes additional fractures in the rock, while a pool of shock-melted rock solidifies in the basin. All the major impact basins on the Moon were created in this way between 3.9 and 4.3 billion years ago. Later, interior heat from radioactivity caused partial melting inside the Moon, and magma rose along the fractures, filling the basin with lava to form a dark mare (right). The lunar maria were filled by this volcanic outpouring between 3.1 and 3.9 billion years ago.

Copyright 2010, Professor Kenneth R. Lang, Tufts University