It is true that the same side of the Moon always faces the Earth, so that we can never see the back side. However, there is a bit of wobble in the Moon's orientation (called libration), which means that features on the edges are seen better in some months than others. Compare the details at the right edge of the Moon in this image to those of the first quarter Moon in the next image, taken a few months earlier. In the next image, the right side is tilted a bit more toward us, revealing more features on that edge.

Image details: A mosaic of two images, one of the north half and another of the south half.  Both halves were based on 10 stacked images, each 1/30^th of a second at ISO 100.

December 2008