We all look to the sky at night and think, "Oh, hey. Cool. The moon is still there."
We know it's the moon because, well, it looks like the moon always looks. Powder white with some grey patches that resemble a particularly bad case of teenage acne.
But we only see half of the moon. The other side, the dark portion facing away from earth, has only been seen by spacecrafts. Turns out the terrain is way different from the bright half, with rare metals such as radioactive potassium, uranium and something called thorium.
Now scientists think that the moon may have once collided with a second, 750-mile-wide moon that was orbiting the earth.
The point is, the moon is the kind of ever-present thing we think we know everything about. And then some pile of hardware flies by and changes the conventional wisdom.
Every year brings a new batch of stuff that updates the books, in a matter of speaking. Here's a bundle of fresh discoveries that were revealed during 2011.