Impact of Color Calibration on Martian Images

摘要

Correct color calibration of images sent from Mars is essential to their usefulness in providing mineralogical, geochemical, chemical and, possibly, biological information. This paper demonstrates the impact of correct calibration on the Viking Mission images. The color charts imaged by the Viking Landers are compared to the color chart on the duplicate Viking Lander at the Smithsonian. When the R, G and B levels obtained from the gray panels are aligned, good agreement is found with the Martian red color panel. The B and G color panels in the Viking image "raw data" as published, however, appear greatly dissimilar to the actual panels viewed on Earth. An excess of red is found on all of the Martian blue and green panels. Limits on the multiplicative intensity properties are derived showing that only extreme red illumination could change the Martian B and G color charts so dramatically. Such extreme illuminations are shown to be incompatible with the gray panels. It appears that the true raw image data have been modified prior to publication to convert the blue and green pixels to gray, rendering a grossly changed image.