"Pieter Litchfield" wrote:

As a (B&W) photographer, I am very sensitive to the subtle changes that
changes in camera position, changes in light intensity and position, and
changes in exposure can have on a picture. In looking very carefully at
many of the MSNBC slide show shots "showing" the beds of purported recent
water flows on Mars I can see those same, or very similar tracks on the
"before" pictures. Certainly the "after" pictures could have been
positioned, timed, and exposed to reveal or enhance details that were in the
shadows in the "before" pictures.

Look at them very carefully. I think there may be less here than meets the
eye.

The NASA TV briefing covered the subject of illumination and in fact the images
released were taken at the same Sun angle and season -- they've worked
very hard to make sure they are not being fooled by such.