The face you see in the photos is merely an illusion to you. The face is a huge rock formation which resembles a head formed by shadows giving the illusion of eyes, mouth, nose, etc. There has been three photos taken of this rock formation since 1976, since the 1976 photo the camera resolution, meaning the focus of the camera, has improved. Since the resolution of these cameras have improved you can see clearly that there is not actually a face on the surface of Mars. It is just merely a large buldge of rocks.

The face you may have once saw is only a shadow of a rock formation. NASA's Viking 1 spacecraft was circling the planet to look for its sister ships possible landing sight when they found the rock formation, then they snapped pictures of the rocks. Remember the camera resolution was not as clear in this time period.

Due to the scientific studies and the fact of the camera resolutions we have found that there is not an alien life force on the surface of Mars. The only thing we've found are rock formations. The most recent picture taken was at least tens times sharper than the ones before, revealing it is just a natural land form.