Now, major impacts have ceased and lavas haven't flowed for a very long time. When you look at the Moon, you are looking at a very old surface. It's a surface that hasn't been covered up or washed away by wind and rain, a surface that hasn't been reworked by the processes of plate tectonics like here on Earth. The lunar rocks hold a record of the Moon's past, and tell an ancient story. It is a dramatic tale of great cataclysmic impacts, of billions of years of meteorites battering the lunar surface, of hot lavas pouring out onto the surface for hundreds of millions of years. And it is Earth's story too. Because when the Moon's surface was being bombarded, so was the Earth's, but that record has been obliterated here at home.