Could be a camera artifact.
Don't see how it could be a camera artifact, holds position on the topography as the camera angle and rover position changes.
A camera artifact would change position on the topography as the rover and camera moved.
Can probably say the same for the sun hitting a *glimmering rock*.
You don't have to move too far watching a mirror reflecting sunlight in the distance for the bright image to change or disappear all together.
Just weird enough for NASA not to investigate further..........Again :)