Does This Photo Show A Human Skull On Mars? [Picture]

Recently, this picture has surfaced that was taken on Mars by the Spirit rover that shows what some are calling a "human like" skull, and some are calling a rock. What do YOU think?

There are a few photos of this floating around the internet that have been altered, but this one is from NASA and is unaltered.

Could it just be a kooky coincidence this rock looks very much like a human skull?