Looking at Spirit's equivalents, I think we can resolve the issue.

IMO, the smaller dot in each image is the Sun itself. The larger dot is a series of internal reflections and lens artefacts, common if one views a bright near-point source. Notice for Spirit (you may need to go to the original image here), that there are a sting of three false Suns, all aligned at 5 o'clock opposite the true Sun at ~11 o'clock on a line through the axis of the lens. For Opportunity, the Sun is more nearly centred and at 3 o'clock and the patch of light at 9 o'clock is a composite of the 3+ false Suns, IMO.

If you take the EFF 1024x1024 image and crop down to a 63 x 63 image, as for the ESF image, the big blob is way too big to be the same as the Sun in the ESF images, but the smaller blob is about right, allowing for some fuzzy compression.