rondhamalam: Why stitching 55 images of 2MP while they can make out of only 4 images using D800.
NASA is not that smart.
There was an article before the launch of the rover discussing about why they chose to use such ja low res camera (by earthly standards).
Without reading it, my humble guess is that sending 55 2mpix files back to Earth might be a bit less frustrating than sending 4 30+ mpix files. I would guess they didn't make a download manager for the rover to support resuming downloads if the connection happened to break.
I might be totally wrong, just guessing.
Nevertheless, framing, capturing and stitching those 55 files together to create such a flawless image is simply an astonishing achievement especially when the camera is on another planet.