Cydonia is a region on the planet Mars, and has attracted both scientific and popular interest. The name originally referred to the albedo feature (distinctively coloured area) that was visible from Earthbound telescopes. The area borders plains of Acidalia Planitia and the Arabia Terra highlands.
The area includes the Mars regions: “Cydonia Mensae”, an area of flat-topped mesa-like features, “Cydonia Colles”, a region of small hills or knobs, and “Cydonia Labyrinthus”, a complex of intersecting valleys. As with other albedo features on Mars, the name Cydonia was drawn from classical antiquity, in this case from Kydonia, a historic polis (or “city-state”) on the island of Crete.
Cydonia contains the “face on Mars” feature — located about half-way between Arandas Crater and Bamberg Crater The ESA “skull” formation is a few kilometres south of the “face”.
Cydonia lies in the planet’s northern hemisphere in a transitional zone between the heavily cratered regions to the South, and relatively smooth plains to the North. Some planetologists believe that the northern plains may once have been ocean beds and that Cydonia may have been a coastal zone.
“Face on Mars”
One of the features in the Cydonia region, the “face on Mars” (about 1.5 kilometers (one mile) across), has had special notoriety in Western culture since it was imaged in 1976, because it looks like a face. This naturally occurring pareidolia has also inspired science fiction literature which typically assume it is a non-natural structure. For comparison, an example of naturally occurring pareidolia on Earth is New Hampshire’s Old Man of the Mountain.
In one of the images taken by Viking 1 on July 25, 1976, a 2 km (1.2 miles) long Cydonian mesa, situated at 40.75° north latitude and 9.46° west longitude, had the appearance of a humanoid “Face on Mars”. When the image was originally acquired, Viking chief scientist Gerry Soffen dismissed the “face” in image 35A72[ as a “[trick] of light and shadow”. However, a second image, 70A13, also shows the “Face”, and was acquired 35 Viking orbits later at a different sun-angle from the 35A72 image. This latter discovery was made independently by Vincent DiPietro and Gregory Molenaar, two computer engineers at NASA’s Goddard Space Flight Center. DiPietro and Molenaar discovered the two misfiled images, Viking frames 35A72 and 70A13, while searching through NASA archives.
Cydonia was first imaged in detail by the Viking 1 and Viking 2 orbiters. Eighteen images of the Cydonia region were taken by the orbiters, of which seven have resolutions better than 250 m/pixel (820 ft/pixel). The other eleven images have resolutions worse than 550 m/pixel (1800 ft/pixel) and are virtually useless for studying surface features. Of the seven good images, the lighting and time at which two pairs of images were taken are so close as to reduce the number to five distinct images. The Mission to Mars: Viking Orbiter Images of Mars CD-ROM image numbers for these are: 35A72 (VO-1010), 70A13 (VO-1011), 561A25 (VO-1021), 673B56 & 673B54 (VO-1063), and 753A33 & 753A34 (VO-1028). Parts of the region were subsequently imaged at far higher resolution by the Mars Global Surveyor, Mars Express and Mars Reconnaissance Orbiter missions.
More than 20 years after the Viking 1 images were taken, a succession of spacecraft visited Mars and collected new data from the Cydonia region. These spacecraft have included NASA’s Mars Global Surveyor (1997–2006) and Mars Reconnaissance Orbiter (2006-), and the European Space Agency’s Mars Express probe (2003-). In contrast to the relatively low resolution of the Viking images of Cydonia, these new platforms afford much improved resolution. For instance, the Mars Express images are at a resolution of 14 m/pixel (46 ft/pixel) or better. By combining data from the High Resolution Stereo Camera (HRSC) on the Mars Express probe and the Mars Orbiter Camera (MOC) on board NASA’s Mars Global Surveyor it has been possible to create a 3D representation of the “Face on Mars”.
When it was first imaged, and into the 21st century, the “Face” is near universally accepted to be an optical illusion, an example of pareidolia. After analysis of the higher resolution Mars Global Surveyor data NASA stated that “a detailed analysis of multiple images of this feature reveals a natural looking Martian hill whose illusory face-like appearance depends on the viewing angle and angle of illumination”. Similar optical illusions can be found in the geology of Earth; examples include the Old Man of the Mountain, the Pedra da Gávea, the Old Man of Hoy and the Badlands Guardian.
The Cydonia facial pareidolia inspired individuals and organizations interested in extraterrestrial intelligence and visitations to Earth, and the images were published in this context in 1977. Some commentators, most notably Richard C. Hoagland, believe the “Face” to be evidence of a long-lost Martian civilization along with other features they believe are present, such as apparent pyramids, which they argue are part of a ruined city.
While accepting the “face” as a subject for scientific study, astronomer Carl Sagan criticized much of the speculation concerning it in the chapter “The Man in the Moon and the Face on Mars” in his book The Demon-Haunted World. The “Face” is also a common topic among skeptics groups, who use it as an example of credulity. They point out that there are other faces on Mars, often much clearer, but their images do not elicit the same level of study. An example is the Galle Crater, which can show a rendition of a smiley, or a profile of Kermit the Frog, or other celebrities. Discover magazine’s Skeptical Eye column ridiculed Hoagland’s claims, asking if he believed the aliens were fans of Sesame Street.