Nothing is 'hidden'— the image is a stitched panorama from many smaller images, and they didn't (yet?) transfer some of the images which only cover the rover, p

Nothing is 'hidden'— the image is a stitched panorama from many smaller images, and they didn't (yet?) transfer some of the images which only cover the rover, presumably because looking at the rover is scientifically uninteresting. The black areas are just the boundaries of the missing images.