"To peer inside the moon, scientists used measurements from two NASA satellites called Ebb and Flow, collectively known as the Gravity Recovery and Interior Laboratory (GRAIL) mission. By measuring the tiny fluctuations in the moon's gravitational field, they have indicated that, in its first billion years, the moon (and, by inference, many of the inner planets) was fractured repeatedly by violent impacts from asteroids and other remnants from the early years of the solar system."
16 December 2012
Gravity Map ~ NASA's GRAIL Images of Moon!
Alok Jha of the Guardian spots NASA's GRAIL mission to map our Moon's gravity!