What the Mars Global Surveyor MOLA Reveals about the Mars Face
(and what it reveals about JPL)




NOTE: This is a somewhat condensed version of a more technically oriented paper published in the new online journal, New Frontiers in Science. I strongly encourage readers to consider subscribing to that journal for objective scientific presentations on subject matter currently unpopular with the so-called "scientific mainstream." The article below concentrates more on the political implications of JPL's treatment of the Mars Face. This focus seems appropriate because it is evident that the management at JPL views the Face as a political problem, not as a scientific issue.
 
 

On April 8th, 2001, the Mars Global Surveyor (MGS) acquired a full image of the "Face" on Mars. After an unexplained six-week delay, the image was publicly released. The release of the image was accompanied by the nearly simultaneous posting of a "news article"  on an official NASA web site. The intent of the article was apparently to render a definitive scientific conclusion that the Face is an unremarkable hill or mesa. The posting of the article on a NASA web site implies that the National Aeronautics and Space Administration officially endorses the methods and conclusions represented.

The NASA article states:

"The laser altimetry data are perhaps even more convincing than overhead photos that the Face is natural. 3D elevation maps reveal the formation from any angle, unaltered by lights and shadow. There are no eyes, no nose, and no mouth!"
This is really a tacit admission that the image by itself fails to support JPL's claims that the Face is an ordinary mesa. They need another source of data to help explain away the fact that clear indications of facial features and symmetry, however incomplete, persist in all visual images to date regardless of lighting conditions.

The JPL "elevation map," which has never been released, was purportedly created by combining the visual Mars Orbiter Camera (MOC) image with elevation data acquired by the Mars Orbiter Laser Altimeter (MOLA). The fallacious claims made about the resolution of the MOLA instrument are described elsewhere and won't be repeated here.

The article shows a "3D perspective" image (Figure 1) created from this elevation map. This image, like JPL's "Catbox" enhancement of the previous MOC image of 1998, shows a surprisingly flat landform. The Catbox was created by misuse of high-pass filtering. This image has been created by misuse of the MOLA data, as will be shown subsequently.

A caption in one of the images in the article states that

"the peak of the mesa-like landform rises 800 feet[240 meters] above the surrounding plain"
Presumably this height is based on the MOLA measurements. The distance of 800 feet, or 240 meters, is less than 10% of the landform's length, which is about 2600 meters. Previous analyses by Mark Carlotto indicated the landform's height to be 412.5 ± 17.5 meters. Carlotto's figure was supported by two different methods: a simple measurement of the length of the landform's shadow in an earlier Viking Orbiter image and by a more sophisticated shape-from-shading (SFS) analysis of two of the Viking images.

The NASA height estimate is 42% lower than Carlotto's earlier estimate. The difference is much too great to attribute to the low (47 meter) resolution of the Viking images employed in Carlotto's earlier analysis. If the peak height cited in the NASA article were correct, it would mean that Carlotto's methods were erroneous. But it is not correct, as examination of the actual MOLA data for the Face landform proves.
 
 

Figure 1 Image from the May 24th, 2001 "Science@NASA" article on the Mars Face. The NASA caption reads in part: "A 3D perspective view of the Face on Mars landform produced by Jim Garvin (NASA) and Jim Frawley (Herring Bay Geophysics) from the latest MOC image (April 8, 2001) and all of the available laser altimeter elevation measurements by MOLA. There is no vertical exaggeration in this ray-traced image" (The landform was presented upside-down relative to its orientation in the Viking images with which most people are familiar.)

While the article does not give any information on the MOLA data used to construct the elevation map, the MOLA science team has provided an online database of MOLA measurements that I used to find it. The elevation data collected for any area on the surface of Mars may be retrieved with a JAVA application called "molafind."

Locating the Face in the MOLA data was not a simple matter of entering coordinates and retrieving the data. It was necessary to find the data for the Face within the frame of reference of identifiable surface features in a large-area elevation map. To do this, I wrote a program that constructs a visual gray-scale representation of the MOLA data (i.e., an elevation map) for the region of the planet surface around the landform. The relationship on the elevation map between pixel brightness and surface elevation is linear: the brighter the pixel, the greater the height.

As the two-dimensional pixel array for the visual image is constructed, the program records the orbit numbers for the MOLA data points contributing to the value of each pixel in the elevation map.

I wrote a second program that constructs the graph of the elevation profile for any selected orbit crossing a point of interest on the elevation map. This program converts the areocentric coordinates of each data point for the orbit to linear distances, with each degree of latitude equaling 59 kilometers and each degree of longitude equaling 59 kilometers times the cosine of latitude.

The match between a unique group of three craters in the elevation map to craters visible in an earlier MGS wide-angle camera image provided the key for identifying all other prominent landforms in the area, including the Mars Face. Both the MOLA and camera images are shown in Figure 2. The MOC image has been orthorectified and adjusted in size and orientation to match the MOLA image. The labels identify common features in both images as follows:

The match between the two images of the length and orientation of a line connecting any two of the labeled features is virtually exact. A close correspondence between other patches of bright pixels in the MOLA image with prominent hills or mountains in the MOC image can be seen throughout area. There seems little reason to doubt that Feature "B" is the Mars Face; there is no other prominent elevated feature for several kilometers in any direction.

By chance, two nearly congruent orbital tracks crossed the Face: 10062 and 16677. These have been combined into a single profile to improve the profile resolution somewhat above the more typical 300 meters (the NASA article incorrectly states the resolution as 150 meters). The result is shown in Figure 3. A line has been drawn on the graph to indicate the distance of 240 meters (800 feet) that the NASA article stated is the height of the landform at its peak. It can be seen that the length of this line falls noticeably short of the distance from the maximum height of this profile to the surrounding plain. The unexpectedly low height claimed by NASA is a completely arbitrary and meaningless number. The true height of the Face through the cross section shown is about 330 meters. The Face is at least 90 meters higher than the value given in the NASA article.
 


Figure 2 Left: Visual representation of MOLA data over an area 40km wide and 103km long centered on the expected coordinates of the Face. Right: Section of wide-angle MOC SP125801, the third Cydonia image taken in April 1998. Positions are labeled in the two images to show the correspondence of their positions. The feature at position "B" is the Face.
 
 

Figure 3 Top: Plot of data points across the Mars Face for Orbits 10062 and 16677. Bottom: Same graph with points connected by straight-line segments and labeled with dimensions. Heights have not been exaggerated. The highest point on the profile is at 40.74813N 350.29864E in areocentric coordinates.
 
 

A height of 330 meters is also about 65 meters short of Carlotto's estimate. However, there is no reason to suppose that a MOLA laser shot actually hit the landform at its peak on either of the two MGS passes over the Face. The landform can be higher than any of the points measured by the MOLA instrument but it cannot be 90 meters lower as JPL claims.

Another important fact revealed by this profile is that the terrain is extremely level a few hundred meters to either side of the Face. This makes it less likely that there is a significant slope down from the Face landform in any other direction. Such a downward slope in the direction of the sun azimuth in the Viking images would have caused the landform to cast a shadow longer than it would have been on level terrain, leading to an overestimate of its height based on the shadow length. This profile, then, provides support for the validity of Carlotto's shadow-length estimate.
 

Comparison of MOLA and Shape-From-Shading Profiles

In any scientific inquiry, of major interest is the assessment of the accuracy of past predictions in light of more recent data. Obviously, then, a comparison is warranted between the MGS MOLA profile of the Face and a profile extracted from Carlotto's shape-from-shading (SFS) model. Carlotto constructed the elevation map shown in Figure 4 from the Viking SFS elevation model. The relationship between pixel brightness in the elevation map and the corresponding elevation of the SFS model is linear, just as it was for the visual representation of the MOLA elevation data of Figure 5.

Figure 4 Elevation map generated from the Viking shape-from-shading model courtesy of Mark Carlotto. The red box outlines the section used to generate a profile comparable to the MGS MOLA profile. The MGS orbital track was oriented at an angle of approximately 37° to the long axis of the Face landform as shown.

Extraction of a profile from the elevation map is simply a matter of converting the average brightness for each row of pixels in a narrow column representing the MOLA track to a vertical distance plotted against the horizontal position of the row in the column. The spatial scale of the elevation map is approximately 11 meters per pixel, so a column width of 10 pixels, or 110 meters, was chosen to approximate the 130-meter width of the MOLA laser spots for construction of SFS profiles.

The average gray scale number of each row in the chosen column of the elevation map was multiplied by a constant factor to convert from brightness to a height in meters. Carlotto estimated the maximum height of the Face as between 395 and 430 meters. Therefore, the maximum gray scale number of 255 was assumed to correspond to a height of 400 meters, an elevation near the low end of the range of the peak height of the Face estimated from the SFS model. The gray scale values in the region at the base of the Face on the elevation map are around 30. The conversion factor in meters per gray scale number was therefore taken to be 400/(255 -30), or 1.78 meters of elevation per gray scale number,

The precise spatial relationships of the two MOLA tracks to positions on the elevation map are unknown. However, the known inclination of the MOLA track to the long axis of the Face is sufficiently great to put strong constraints on the range of possible positions of the tracks relative to the elevation map. The long axis of the Face is oriented approximately 30° west of north while the MOLA track is oriented 7° east of north. The MOLA track therefore crossed the Face on a diagonal line ~37° clockwise from a parallel orientation to the long axis of the landform. The MOLA track had to pass close to the landform's central point. Had it crossed the Face at a position very far off to either the left or right of the position of the column shown in Figure 6, the MOLA profile would have been considerably narrower than its actual width. As was shown in Figure 3, the width of the profile is somewhat less than 3000 meters while the length of the long axis of the landform is about 2600 meters as measured on MGS and Viking images.

To see if there was a match between the contours of the elevation map and the MOLA profile, I constructed SFS profiles for several 10-pixel wide strips to either side of the central point on the elevation map. Each sample strip was parallel to the orientation of the MOLA track. Differences in height and shape from the actual MOLA profile precluded all but the one shown on the elevation map in Figure 6. It can be seen in Figure 5 that the match is very close. The lack of the higher-frequency contours on the MOLA profile that are present in the SFS profile can probably be attributed to the lower resolution of the MOLA instrument relative to that of the SFS map (the MOLA spots are spaced slightly less than 300 meters apart while the resolution of the Viking images on which the SFS model is based was ~50 meters).

Figure 5 SFS Profile (blue) for the strip of the elevation map indicated in Figure 4 superimposed on the actual MOLA profile (red) of Figure 3.
 
 

To get another perspective for the MOLA profile, it was compared to another SFS profile taken along the centerline of the Face that includes the highest point on the elevation map. In other words, this SFS profile is a side view to which the word "profile" most commonly refers in the context of a description of a face. The relationship between this SFS profile and the plausible position of the MOLA track on the elevation map is shown in figure 6. The resulting SFS profile is shown in Figure 7 superimposed on the MOLA profile. Because the orientation of the MOLA track is about 37° out of the plane of the side view of this graphic, the MOLA profile has been reduced in width by the cosine of 37° to give it the shape it would have when viewed from this perspective.
 
 

Figure 6 SFS Elevation Map showing strip through centerline of Face (blue) and its relationship to a plausible path of the MOLA across the Face.

To provide a visual context for the MOLA profile, it is also shown superimposed on a side view of the Face created by the artist Kynthia. For over a decade, Kynthia has applied her skills as a sculptor to translate the 2-dimensional images from Viking and MGS into her perception of the 3-dimensional form. While there are differences between the computer-generated SFS profile and the artistic rendering, the general contours are the same. The MOLA profile fits both nearly equally well.
 
 

Figure 7 Top: MOLA profile (red) superimposed on a profile from the SFS elevation map along the centerline of the Face. Bottom: MOLA track (black) superimposed on an artistic depiction of a side view of the Face (courtesy Kynthia). The broken line segments indicate those parts of the MOLA track on surfaces not visible from this perspective, which is a view from the west looking east (north is to the left).
 

CONCLUSION

The May 24th NASA article quotes James Garvin, chief scientist for NASA's Mars Exploration Program as stating:
  "We took hundreds of altitude measurements of the mesa-like features around Cydonia, including the Face. The height of the Face, its volume and aspect ratio -- all of its dimensions, in fact -- are similar to the other mesas. It's not exotic in any way." That the two low-resolution profiles of the Face reveal nothing "exotic" cannot be disputed, but nothing exotic about the shape revealed by the meager MOLA data could be expected. The profiles do, however, reveal that the NASA 3-dimensional reconstructions of the landform based on the MOLA data are in serious error. They may, conceivably, have even been based on a MOLA profile of the wrong landform. (JPL's apparent use of MOLA data for the wrong landform is covered in detail in the New Frontiers in Science paper). Perhaps a mistake was made in the haste of preparing the public relations material for the article in time for its release to coincide with the release of the MOC image. This is a matter of conjecture since no details of the reconstruction process were given in the article. Queries made to the article's author and to the web page curator have not been answered.

Regardless of the cause of the error, the landform is, at a minimum, 37% higher and probably more like 67% higher than the estimate made by NASA. All conclusions presented in the NASA article based upon the MOLA data are therefore invalid -- most notably, the claim  that  elevation maps based on the MOLA data show that  face-like features apparent in all the visual images can be explained as tricks of lighting.

The MOLA profile is not only consistent with Carlotto's height estimates but conforms in shape as well. The close match provides grounds for increased confidence in the validity of the SFS model. The NASA article cited the MOLA data to support the assertion that features resembling those of a face do not really exist as three-dimensional contours on this landform. To the contrary, the conformity of the MOLA data to the SFS model supports the reality of the unusual features predicted by Carlotto's model.

While scientists at JPL may be highly competent in geology, physics, and chemistry, the facts show that for some reason, they cannot do a competent job when it comes to evaluating possible evidence of past life on Mars, especially intelligent life. The obvious hostility they have for such possibilities seems the most likely explanation for this selective incompetence. As shown by a recent "hit piece" written by an individual associated with JPL about the work of several respected Hungarian scientists, this seemingly irrational hostility appears to extend even to researchers who merely propose that there is evidence of microbial life on Mars.

Some people argue that the geologists and physical scientists with JPL would be "pleased" to find evidence of intelligent life on Mars because it would mean more money for their budget. That does not make sense; the money would go to archeologists and biologists, not to them. In any case, such arguments are irrelevant because the facts, as demonstrated here and in other articles on this web site, show that they would be anything but pleased. If proof of life on another planet within the solar system is ever discovered, it will not be done by JPL, at least as it is presently constituted.

-- Lan Fleming