Since June 2009, NASA's Lunar Reconnaissance Orbiter has been circling the moon, compiling data for the first full topographic map of the moon's surface, suggesting that 3.9 billion years ago asteroids pounded the moon and Earth, likely evaporating water supplies.
The data is part of Science magazine's September 17 issue, by lead author James Head of Brown University, who says, "The moon is thus analogous to a Rosetta stone for understanding the bombardment history of the Earth. Like the Rosetta stone, the lunar record can be used to translate the 'hieroglyphics' of the poorly preserved impact record on Earth."
More images from the Lunar Reconnaissance Orbiter can be seen here.
[Images via NASA]