A little isomnia...

Thanks for describing what happened with the Viking calibration procedure. Kind of reminds me of the Hubble null corrector...

Reference calibration does not require humans to go to Mars and look around. A standard light source used to illuminate the reference for images taken at night will do.

My guess is that the reason all those people make amateur attempts to correct the colors of the Viking images is because NASA spends no money for professionals to do it, and some people would like to have the data. The same goes for improving Viking image resolution through post processing - NASA funding for this is zero.

Agree that many big rocks (and how's that for a geological term?) appear grey. The next question is whether the soil underneath the immediate surface is gray as well, which is seen anyplace where it is not covered with iron dust.

I thought the other terms you used for color were from a fashion designer until I realized they have well defined geological meanings. Besides the colors you mentioned, the rocks on the surface of Mars also show black from impact blasts. Given limited geological processes, the iron dust strikes me as being the result of the impacts of iron asteroids with Mars.

The big question is whether color correction to a white sky would lead to "true" geological colors.

On the topic of display and printing, don't know if its of any help, but there used to be true color equipment to set up Macs. I don't know what is available now.

EP