The left image is a portion of Viking Orbiter 1 frame 070A13 (taken in the mid-1970s and the cause of so many people saying that there is a face on Mars that proves the existence of extraterrestrials), the middle image
is a portion of MOC frame 22003 (taken in April of 1998) shown normally, and the right image is the same MOC frame but with the contrast reversed
(that is, light features were forced to be dark, and dark features were forced to be light) to simulate the approximate lighting
conditions of the Viking image.
