"Cousin Ricky" <ric### [at] yahoocom> wrote:
> The redness that you see when you look at Mars in the sky is an effect created
> by your vision due to the contrast between the sunlit Mars and the black sky.
> The redness you see in surface images is due to Hollywood or NASA giving the
> public what they want.  The Viking images (1976) are just plain prostitution.

Which of the zillion version of them? :)

Ironically, the first release of the Viking image wasn't custom-tailored to some
specific soil color at all - instead, someone responsible for color calibration
had thought that a greenish-brown sky looked odd...

These pages look like the guy knows what he's writing about:

http://www.donaldedavis.com/2002_addons/SSYCOLRS.html
http://www.donaldedavis.com/PARTS/MARSCLRS.html


Color calibration of martian imagery is a difficult thing. Yes, the probes did
carry color calibration charts with them - but they don't really help, because
(as we POVers should know) their appearance not only depends on camera
calibration, but also on illumination.

Strictly speaking, all the color charts can help you do is calibrate your shots
so that the sky looks perfectly gray. In reality, it will have a different
color - but which?


Even then, martian soil and martian soil don't look the same. It strongly
depends on a probe's landing site. The same goes for the sky: It depends on the
amount of dust in the atmosphere, which varies over time.

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