[X] My Assistant

[Fran Ontanaya]

I thought it could be amusing to try this:



It's a composite of rear hazcams from sols 1256, 1264 and 1268 with enhanced, unaltered colors. Oppy didn't move during those days, and took images of the storm at roughly the same time each sol. Since tau was changing, the color of the ambient light must have been different in each one --apparently enough to distinguish the blueberries and some bright rover pieces, and perhaps the sky and the dust too.

[Fran Ontanaya]

Hum, I loaded three pictures from the same Sol, sorted them and composited them as RGB, nothing else.

I'm not convinced now that any of the pictures shows much if any spectral data. Maybe only color changes in a flat, featureless surface can be slightly meaningful.

I.e. in this one you can see that the features that face the rover are redder, and everything else bluish, due to changing shadows/reflections.

[Nirgal]

Hum, I loaded three pictures from the same Sol, sorted them and composited them as RGB, nothing else.

I'm not convinced now that any of the pictures shows much if any spectral data. Maybe only color changes in a flat, featureless surface can be slightly meaningful.

I.e. in this one you can see that the features that face the rover are redder, and everything else bluish, due to changing shadows/reflections.

----> EDIT: I was too premature in my conclusion: Although there is multi-dimensional structure in the data, it could be due to different light source angles rather than spectral properties of the objects ....

Also note the distinctly colored details at the rock (a crop I did from your image above where I directly used the principal components
for the false color composite)

[ugordan]

Also note the distinctly colored details at the rock (a crop I did from your image above where I directly used the principal components
for the false color composite)

The distinct color of the rocks comes from their rugged texture and changing illumination. It's not a coincidence that the ground appears more bland because it's pretty flat and the sand grains look similar at different illumination angles. Some of the rocks appear bland in color due to their face being illuminated more or less the same by sunlight at different times of sol, but other rocks are angled such that significant shadowing occurs at certain times and hence these "filter" differences.

I'm sorry, but I just cannot believe a slight solar elevation angle alone could cause such a different illumination color so as to act as a filter for the three exposures. The last composite frames in particular had to be taken with sun high up within a couple of hours. How much does daylight color appear to change around noon on Earth? I expect the same on Mars.

Moreover since the intrinsic color variations in rocks and soil are very subtle in "natural" color, they're only distinct in false color composites. This method, at best, would generate images at *slightly* different colors and even then, it would be only useful if you could freeze the illumination angle.