Cydonia Update

by Mark Carlotto


In April 1998, the Mars Global Surveyor obtained three high resolution images over the region in Cydonia containing the City and Face. Although NASA and JPL immediately dismissed the Face and other objects as natural surface features, research presented at the 1998 American Geophysical Union (AGU) Spring Meeting in Boston suggested otherwise (Carlotto and Brandenburg 1998). Detailed analysis of the Face showed a very high degree of lateral symmetry in the platform, found additional facial features (lips and nostrils) located along the central axis of symmetry, and confirmed the presence of unusual linear features on the head.

Continued research over the past year has revealed other anomalies in these images including strange features at the base of the City Pyramid and Face, what appears to be ice at the bottom of at least one crater in the area (Moore et al 1999), further indications of sedimentary rock and water erosion in this part of Mars (Erjavec and Brandenburg 1999), and various quasi-geometric patterns including a triangularly shaped feature north of the City (McDaniel 1998).

This report summarizes several new findings over this area:

It is well known that the bottom of the first MGS strip containing the Face also imaged a portion of the D&M Pyramid. On closer examination it appears that the entire northeast quadrant of the D&M was imaged as well.

Analysis of this new image of the D&M reveals a structure similar in certain ways to the City Pyramid.

In addition to the City Square and City Pyramid, the western portion of the Fort was imaged in the third MGS strip. Coincidentally it is located immediately to the east of several recently discovered craters thought to contain ice.

Review of MGS Imagery

The image acquisition parameters for the three April 1998 MGS images over Cydonia: 22003, 23903, and 25803 are summarized in Table 1. The emission angle is the camera's tilt from the vertical . The incidence angle is the angle of the sun from the vertical. This information was obtained from an on-line CD collection of MGS images (USGS 1999) acquired during the aerobraking and science phasing orbits. It does not include the azimuth angles of the sun and the spacecraft. Peter Nerbun has calculated the approximate solar and spacecraft azimuths for 22003 to be 159 and 232 degrees, respectively. Because all three images were taken within a few weeks the solar angles are only a few degrees apart. On the other hand there is a considerable range of emission angles, from about 45 degrees off vertical for the MGS image of the Face (22003) to almost directly overhead (23903). As a result the image quality varies from the hazy oblique image of the Face (22003) to the higher resolution and better contrast overhead views of the City (23903 and 25803).









Resolution (meters)




Emission Angle




Incidence Angle




Phase Angle




Center Longitude




Center Latitude




Table 1 Image acquisition parameters for three images over main Cydonia site

To get a better idea of exactly what was imaged by MGS, the three image strips were registered to a map projected version of Viking image 35A72. Fig. 1 shows the region over the City including the southwest corner of the Fort.


Fig. 1 Portions of MGS images 25803 and 23903 (left) and corresponding Viking image 35A72 (right).

Even though the sun angles are different, the MGS and Viking images in Fig. 1 are easy to correlate because they were taken from roughly the same position overhead. This was not the case in the MGS image containing the Face and D&M Pyramid (Fig. 2) which was acquired about 45 degrees off vertical. Because of haze over Cydonia that day, the atmospheric transmission was low (poor image contrast) and the path radiance was high (high ambient illumination). When the ratio of ambient to direct sunlight is high, shadows are weak. Lack of strong shadows, poor image contrast, and patches of frost on the surface (varying albedo) make this image very hard to interpret.


Fig. 2 Portion of MGS image 22003 (left) and corresponding Viking image 35A72 (right).

The Fortress

As noted above, a portion of the Fort was in fact imaged in 23903. A part of that image is shown in Fig. 3. The southwestern corner of the Fort can be seen just above and to the right of the City Pyramid. In the Viking image, this corner is partially shadowed and is suggestive of an opening into the Fort. Lit from below in the MGS image this feature looks like a hemispherical scoop taken from the side of the Fort.

The Fort, like the Face, appears to be severely eroded. An eroded terrace lies to the northwest. Several unusual craters are superposed on top of this feature. One appears to contain ice at its bottom. An article by geologist Harry Moore discusses these craters in greater detail (Moore et al, 1999).

Fig. 3 Portion of 25803 showing western portion of Fort and craters thought to contain water ice

The D&M Pyramid

By comparing MGS image 22003 with an earlier Viking image of the D&M pyramid, it is clear that the entire northeast quadrant of the object was imaged at the bottom of that strip. As in the upper portion of the strip containing the Face, lack of shadows makes it extremely difficult to analyze the D&M. At a 45 degree depression angle, a flat surface is foreshortened by about 30%. Because we are looking at the northeastern sides of the D&M, which are sloped away from the observer, the foreshortening is much more severe. Like the Face, we are seeing very little of the right side of the D&M because of the camera angle.

In Viking imagery, the three illuminated faces of the D&M appear to be relatively flat with well defined edges in between. Buttress like structures at the base of several edges are also evident. In the MGS image the edge between the northeast and northwest faces resembles a spine running from the apex of the D&M down to the ground. At the base of the spine lies a circular depression, possibly an opening. A dark feature seems to emanate northward from this depression or opening, which then leads into a sinuous channel off to the right. What is this dark feature? A shadow within a deep trench seems unlikely due to the lack of significant shadowing in the image. Another possibility is some kind of dark material flowing out of the D&M.

Fig. 4 D&M Pyramid from 22003 and inset from Viking frame 70A13


The City Pyramid

Perhaps the best image of the Cydonia anomalies is that of the City pyramid (Fig. 5). The sun is high enough in the sky so as to illuminate all sides of the object. The MGS image shows the five sides of the City Pyramid to be similarly shaped with relatively smooth facets divided by spine like edges similar to that seen in the D&M pyramid. Curiously, in this view from the north, the five spines of the pyramid resemble the five pointed Egyptian symbol for a star.


Fig. 5 City Pyramid from 25803 and inset from Viking frame 70A11

What is even more intriguing is that the bases of the City Pyramid, Face, and D&M all seem to have subtle linear and/or rectangular features cut into their sides (Fig. 6). Erjavec has stated that certain geomorphologic features of land forms in Cydonia are suggestive of water erosion (Erjavec and Brandenburg 1999). Can erosion by water or any other agent be responsible for the features seen at the bases of these objects?


Fig. 6 Features cut into bases of City Pyramid (left), Face (middle), and D&M Pyramid (right)



As we await additional photographs over Cydonia, especially of the Face and the Fort, new and subtle patterns are being discovered in existing images. Clearly not the buildings and roads many scientists expected to see. But are they Martian geology, or something else?

In the process of trying to better understand these land forms, researchers have found evidence of water erosion throughout Cydonia including indications of water eroded sedimentary rock (Erjavec and Brandenburg 1999), and liquid water frozen at the bottom of at least one crater in the area (Moore et al 1999). These findings suggest that water was present on Mars far longer than originally thought, and may still be present in Cydonia.

If the Cydonian Hypothesis (Brandenburg et al 1991) is correct, these structures are ancient. But how do we tell the difference between highly eroded natural landforms and artificial structures? In terrestrial archaeology this is a question that is easily answered by digging. But the Mars anomalies are forcing us to think more deeply about this question, to develop metrics for detecting planetary intelligence that go beyond simply finding (or not finding) buildings and roads, metrics that hopefully will be validated one day when archaeologists finally do dig in Cydonia.


M. J. Carlotto and J. E. Brandenburg, "Analysis of Unusual Martian Surface Features: Enigmatic Geology or Archaeological Ruins?," American Geophysical Union 1998 Spring Meeting.

J. L. Erjavec and J. E. Brandenburg, "Evidence for a Paleo-Ocean Shoreline, Sedimentary Features and Water Erosion in Cydonia Mensae," American Geophysical Union 1999 Spring Meeting. Report also available at

H.L. Moore, J.E. Brandenburg, S. Corrick, and A. Sirisena, "Ice Found in Crater in Cydonia," American Geophysical Union 1999 Spring Meeting. Report also available at

J. E. Brandenburg,  V. DiPietro, and G. Molenaar, "The Cydonian hypothesis," Journal of Scientific Exploration, Vol. 5, No. 1, 1991.

Copyright 1999, Mark J. Carlotto

© 2020 Mark J. Carlotto