Earth's Moon Reveals An Ancient Secret. Many astronomers think that during an ancient era, termed the Late Heavy Bombardment, our young Moon was violently battered by a marauding multitude of invading asteroids that crashed onto its newly formed surface. This attack of pelting objects from space occurred about 4 billion years ago, and the shower of crashing asteroids excavated impact craters, and also slashed open deep fissures, in the lunar crust. This sustained shower of merciless impacts increased lunar porosity, and opened up an intertwining network of large seams under the Moon's surface.
Only recently have space missions begun to solve this beguiling Solar System mystery--that a small number of distant moons have been successfully hiding, from the curious eyes of astronomers, life-sustaining liquid water beneath secretive shells of ice.
GRAIL Mission Puts A New Face On The Moon! Scientific investigation into the origin of lunar impact basins has been hampered because there is a general lack of agreement on their size. The majority of the largest impact basins pock-mark the near-side of the Moon (the Moon's enchanting "face"), and have also been filled in by gushing lava streams. These lava streams have covered up, and rendered invisible, important clues pertaining to the shape of the land.