On July 25, 1976, the Viking Orbiter I acquired images in the
northern latitudes of Mars to find a suitable landing site for the
Viking Lander II. JPL recieved an image from the Cydonia region
with a formation that resembled a human face. It released the
image in order to provide the public with an easily recognizable
feature. From the JPL press release:
"The picture shows eroded mesa-like landforms.
The huge rock formation in the center, which resembles a human
head, is formed by shadows giving the illusion of eyes, nose and
mouth. The feature is 1.5 kilometers (one mile) across, with the
sun angle at approximately 20 degrees. The speckled appearance
of the image is due to bit errors, emphasized by enlargement of
the photo. The picture was taken on July 25 from a range of 1873
kilometers (1162 miles)."
JPL could not have predicted the public's response to the image,
which has now become one of the most popular icons of
Mars folklore. While scientists believe that the "face" is
simply a result of lighting on topographical features, there are
theories that the formation was artificially created. Some of these
theories have supposed that the formation was built by an
intelligent civilization on Mars, perhaps as a monument to a Martian deity.
On Sunday, April 1998, the Mars Global Surveyor acquired
images of the "face on Mars", but at ten times the
resolution of the original image, it no longer appeared so convincingly
as a face, but as just another geographical feature on Mars.