Re: Is there... (Interpolation/scaling used in the enlarged image)
"It's flat at the bottom and the rest is diffuse."
That was the very first thing that struck me. The second thing was that there's no pixelisation in the enlarged image - whoops!
If you look at the source image from JPL (jpeg - bah!) the brightened region is just 3 pixels wide by 6 pixels high, so the diffuse appearance in the enlarged image is due to interpolation being employed when the enlarged image was blown up - doh!
What _is_interesting is that only the lower 4 pixels of the central column have been burned out, with the upper two pixels of the central pixel column and both of the two side columns being much less bright, so that you can actually make out the background through them.
I'd say that this isn't a good match for a cosmic ray striking the detector because although the halo pixels could be the result of internal reflection within the layers of the detector they don't spread below the bright column as they do above it; the bright region, even in the raw image, cuts off uniformly across the bottom.
So I had a look at the other image that's referred to and this does have different characteristics; instead of a line of burnt-out pixels there's a 2x2 block, which in itself is not significant because it could indeed be due to the incidence at which the cosmic ray hit the detector, but more importantly, there's a 1 pixel halo of brightened pixels on _all_ sides of the burnt-out region, which is a better match for a cosmic ray striking the detector.
Going back to the first image, I don't think it's a reflection either, because the bottom pixel, for sure, and possibly the one above it as well, in the burnt-out 4 pixel column appear to be coming from a bit of the ground that's in shade - the camera is pointing almost directly towards the sun with the bright region appearing to originate just this side of a ridge, on a slope that's falling towards us.
All things considered, and baring in mind there's aparently a one second time difference between the images from the left and right cameras, I'm more inclined to think that this might have been a small meteorite strike.