Thats not reflection, as in a metallic surface. Its probably reflectance of a substance like a salt or a silicate. Notiv=ce how a crater ejected some material from depth right in the middle , and this stuff has an oxide look.
Also, we can see stress fracs or actual structural lineaments around the entire ejecta area.
A neta thing to note is that PHOTO 7 of Diemos, is a STEREO PAIR.
If you have a stereo viewer you can see Diemos in 3D. (a pair of student stereo glasses will work-I just happen to have a micro view stereo viewer for aerial photos.).
An easier way is to cut out the strip so that you can overlay a same spot by "relaxing" your eyes to gradually cross and you can see the 3D without glasses. (Its a trick that we still teach in aerial photo interpretation classes and survey transfer). Apparently the parallax views were pretty good to get the quality from the scans of Diemos.