The face on the planet is just a natural landform, it just happened to form like a face, because of how the shadows where formed by the small hills.

Acording to the imformation in the article, the image just looks like a face, because how the rocks are formed and the shadows. "It is just another martian mesa, common enogh around Cydonia, only this one had unusual shadows". The shadows gave the illusion of eyes, nose, and mouth. Also the camera did not have the best pixels and they where far away from the planet, so the picture was not the best. It was also a cloudy time of the year on the red planed "April '98". The camera had to peer through wispy clouds to see the face.

What the picture actually shows is the Martain equivalent of a butte or mesa, landforms common around the American West. This is why it is just a natural landform, and not made by the aliens.