30, 20, and 10 Years Ago in OPN

“The ‘Face on Mars’ has been the subject of a small and unusual debate for over 10 years. Initially dismissed by NASA as a trick of light and shadow when it was imaged by a Viking Orbiter in 1976, the ‘face’ was rediscovered by DiPietro and Molenaar several years later. A series of independent investigations followed, which have prompted curious reactions from the planetary science community … Whether it is natural or artificial, the ‘face’ is interesting as an optical phenomena in that it retains its appearance over a wide range of illumination conditions and from a variety of perspectives.”