There are theory that Earth once has two moons more than 4 billion years ago. The theory has been recently opened as to why our moon has two faces. The one visible to us looks low-lying lava while the other side is mountainous.
There are also other theories about the second moon and refer to many names and asymmetry but they still mentioned about the collision of our moon and the second moon (which is the smaller one).
You can read the recent news on http://www.space.com/12529-earth-2-moons-collision-moon-formation.html .
There was also email hoax circulated saying that on August 27 Earth will have two moons. This was since 2003. But what happened on 2003 August 27 only made the Earth and Mars closer than before even in the last 50,000 years.


