I took your obvious bait and tackled the problem...and promptly got my ass kicked.

At first I thought it was just because the images needed serious skewing to fit, because it looks like the camera was pivoting and not just moving smoothly in the lateral axis. But the images still fought tooth-and-nail, and then I realized the problem: Time was passing between frames and the shadows were changing. Even when I could get a rough match of the subtle greys of the rock, the adjacent stark black shadows were badly mismatched.

Oh, and did I mention that the images come in a variety of focal lengths?

I have a lot of respect for the image processing shamans at JPL, but I wonder if even they have magic powerful enough to compensate for such a fundamental mismatch in the scene itself. I'm content to wait and see what our taxpayer dollars hath wrought, while I dress my wounds.