There are many ways that we can come to believe in an idea. Sometimes we even think that we are acting on evidence, when in reality that evidence is fallacious. This Bad Science series is going to point out some common ways our brains can be tricked.
To start with, I have chosen one of my favorites: pareidolia. Think of this as seeing familiar images in the clouds. Our brains are really good at finding patterns. That's why you can look at the bark of a tree or a rock formation and see a face. Once you see that face, it may be hard not to see it. This can make for a fun optical illusion. The problem is when people think that the face in the clouds is real.
In 2001, NASA put any questions to rest regarding this weird formation. The Mars Global Surveyor took a high resolution picture of the same formation when the sun was at a different angle (below). I can still kinda make out where the eye and nose is, but it clearly just a rock formation.
For more see the Skeptics Dictionary
Images courtesy NASA