The Moon's Composition
The Moon possesses a thick outer crust (60 km) and below the crust a mantle (60-1000 km), and a partly liquid core (1000-1740 km). Much of the surface is fractured by massive impact craters formed by meteorites, flooded by molten lava, and carved out from volcanic explosions. The Moon's surface shows the scars of more than 3 billion years of meteorite impacts, most of which developed between 3000 and 4000 million years ago. The youngest Moon rocks are virtually as old as the oldest Earth rocks. The largest craters are approximately 200 km in diameter, while the smallest are only about a meter across. Impact features include crater clusters, dark halo craters, rays, and crater chains. Recent data acquired by the Clementine spacecraft indicates that there is also ice in the bottom of a crater located on the Moon's South pole.