Far-out theory: Earth once had two moons

Earth once had two moons, astronomers now think. But the smaller one smashed into the other in what is being called the "big splat."

The result: Our planet was left with a single bulked-up and ever-so-slightly lopsided moon.

The astronomers came up with the scenario to explain why the moon's far side is so much more hilly than the one that is always facing Earth.

According to the theory, outlined Wednesday in the journal Nature, this happened about 4.4 billion years ago, long before there was any life on Earth to gaze up and see the strange sight of dual moons. The moons were young, formed about 100 million years earlier when a giant planet smashed into …