Color snap-shots from Viking 1 (1)

"...As it has been already discussed in the past, the problems in reconstructing the (true) colors of the Martian Surface and Atmosphere are formidable.
It would be nice to present a folio of color pictures with the unqualified comment that these are the (Real) "Colors of Mars". But, after more than a year (many more, now) of analysis, it becomes clear that the situation will never become so simple.

In order to correct for the out of band spectral leaks in the color filters within the camera it is necessary to have access to both a color and an infrared (JR) picture taken at the same time. Only in that way can the IR contributions to the visible color, a result of camera filter design, be assessed.
For the many color pictures taken without an IR companion detailed calibration is not possible. Instead, the three visible channels-blue, green, and red-are balanced on the assumption that there are no out of band contributions..." (continua)