The Colors of Mars part 2
The MER rovers have returned many hundreds of color images, 'natural' as well as infra red enhanced. Besides the archive of press release images compiled during the course of the mission, The MER imaging team has released a dedicated source of high fidelity Pancam true color images. Jim Bell, the guiding hand behind the site, and his team have excelled in conveying what the cameras are showing us. This site by Damien Bouic (in French) is an excellent collection of panoramas and color products, one of several such excellent sites. The use of calibrated data as it is released to the PDS Imaging Node entails downloading the files desired and using software like NASAView or GIMP, among others, to convert them to formats useable in image editing programs.
At left is a color image showing the 'Spirit' rover color sundial/test chart against the Martian surface. The upper right color chip is a dull yellow ochre. The white parts of the color chart base are overexposed here. The darkness of Martian soil is evident.
At right we see a similar scene, color balanced to match the ground seen behind the sundial. The sky, thus reasonably matched to the color chart, is shown to be strongly tinted with suspended dust which, due to lack of shadowing, appears as a luminous version of the color of the dust draped over the larger rocks.
These MER images (aside from the sundial images above and below, which I color balanced to better resemble the actual color chips) are from the Pancam true color images site, although I have 'fine tuned' them in relation to others in hue, brightness and saturation to attempt matches between the background surface seen with the color chips and wider views made under similar conditions which include the sky. The original image files are works of beauty and undoubtedly the best such color products to use for serious color investigations. Some differences in camera exposure, saturation, and minor color balance issues complicate zeroing in on where to 'anchor' ones color impression. Images containing the ground next to items of known color such as the color charts are the best place to start.
Below: Two photos of the MER sundial target shows the central 'mast' before and after it was painted black to reduce reflections. Otherwise they are identical, with the color chips color balanced to resemble the original, in particular the 'yellow ochre' chip, with verbal descriptions augmenting the available phorographs.
Below is a panorama of the 3 km distant 'Columbia Hills', named after the crew which perished in the last mission of that shuttle orbiter.
Left: an attempt to color balance the sundial chips on the second rover 'Opportunity'.
Left: surroundings with roughly similar color balance as the view to the right, including the sky.
Right: 'down Sun' unshadowed colors of the fine 'soil' of Meridianii with the color chart providing a reasonable color balance.
And for a near natural size closeup of the 'blueberry' laden dust of Meridianii with some hardward in the foreground.
The Phoenix lander has yet to fully tell its tale of the colors around it. Below left is an attempt at a careful color balancing of an early released color image, showing the progress of the adhering of the iron rich fine dust to the outer ring of magnets which tend to protect the inner portions from being discolored.
The colors of Mars-page 3
The colors of the Solar System