Here is another view of the anomalous object rectangled in red. The image is a screen capture at 300% and saved as a png file.
I think that you may have found something here. After closer examination it does not appear to be a compression artefact although when the download is saved there are compression artefacts showing on the saved jpg. This is why I decided to use the screen capture procedure as I could then save the capture as a lossless png rather than a lossy jpg. The object in question would seem to have vertical form but I could only hazard a guess at what it could be.
Note there are no compression artefacts showing in the image so the mesh feature has to be associated with the object. Also, take note of the object showing in the yellow rectangle.
The contrast was increased and the colour saturation decreased slightly. This is the original image and not a colour-difference view.
I do not think what you are seeing is all that strange.
It would appear to me that what you are looking at are jpg compression artefacts that are masking the surface detail.
Before any serious analysis can take place these compression artefacts have to be reduced to a minimum.
Tip - Before you make any adjustments to the image use the soften function in your graphics program and then use sharpen or unsharp mask with care.
Looking at the other images from sol 514, I came across an object of interest. Two images of the same feature are shown below.
The first image is the raw downloaded view zoomed in by 300%, then cropped and saved as a lossless png. The compression artefacts have not been reduced.
Examine the pipe-like feature contained within the yellow ellipse.
The second image is a resampled and cropped jpg image of the same area only it is a colour-difference version. The compression artefacts have been reduced.
I think you will find some interesting objects to explore in this particular image and what there is to observe are not rocks!