I'd have to say that these images from Mars were already "color corrected".

To digress breifly, Robert, the reason why NASA never did much work on color correction is that they did not mind giving Mars a clear blue sky in their press releases - after all, NASA needed to foster the illusion of an Earth-like Mars to justify their institutional existence. In point of fact, in "true color" Mars usually does not look very much like any place anyone would like to live, and this upsets the "true believers" down to their cores. That said, this is the only social process which can explain why NASA let the Viking imagery gather dust for some 25 years, and paid for no work with modern computer image processing techniques to be done on them.

Scientifically, the most useful color correction is to a white light source, which allows the rock spectra to be analyzed for composition. Correcting to this value would also alllow for data on Mars atmospheric dust loading to be extracted, and this data in turn would help with analyzing the "climate" processes on Mars - Mars interaction with the variable Sun.

Myself, I don't mind either the "murk" of true color, or the enhancement to white light values, as long as the white light values are NEVER presented as being the true colors.

BTW, thanks so much for your images and commentary. Your note on the effects of angles of incidence was particuarly well done.

all the best,
ep