The MGS spacecraft took a high-resolution photo of the “Face on Mars” in April, 1998. That image suffered from four handicaps: a low viewing angle; a low Sun angle from the direction under the “chin”; an almost complete lack of contrast; and enough cloudiness to scatter most of the light and eliminate shadows. To add to these difficult circumstances, JPL-MIPL personnel, apparently judging that the controversy over artificiality would not be ended when the actual photo was released, processed the image through two filters having the effect of flattening and suppressing image details. This step is documented at a JPL web site.
Before I studied image processing myself, I worried that the biases of the person doing the processing might contribute significantly to the image seen. Now that I am more familiar with the process, I can see that it uses objective, standardized computer techniques, and does not add features to an image that are not present in the original. The techniques used are more like focusing a camera – they change the camera’s view to one more like what the human eye would see if viewing directly. The exception is the left portion of the east (right-side) eye, which was hidden behind the nose ridge, and for which no data exists other than that in Figure 1. It was therefore filled out artistically by assuming symmetry with the other eye socket. ** [See footnote at end.] **
The JPL personnel who decided to release Figure 3 to the media were right about one thing. If they had released the unfiltered spacecraft image to the press, the controversy over artificiality of the Face would not have been settled in the minds of many fair-minded people.
In fact they are not computer modified, they are simply reversing the image manipulation JPL did to make it look less convincing, and showing how it really should look from an overhead angle and lit up evenly. This does not add any extra details to the picture - it simply shows it how it would look if we saw it. Meanwhile if you accuse them of modification, JPL has actually admitted to modifying the high-resolution images, by apply a high-pass and a low-pass filter to the image. Open up photoshop, and apply these filters to an image.