Right, hills and valleys would tend to change shadow directions, as we see throughout the entire image, we can agree however there is likely a relatively low angle of light source, coming primarily from near absolute left, and there are shadows with various degrees off of that axis. It is however difficult to determine what a shadow is and what a crevice is in places, as there are no cars and trucks that we have intrinsic knowledge of separating those objects from surrounding areas. That's one of the main problems with viewing alien landscapes, no local color, and also in a point of view we rarely have in day to day life, from directly above, (unless you walk around all the time with your head down). To make matters even more challenging is we get only one view, with one light source, so the information we can gather is limited.

The sunlit spot in the OP's picture (the spot which I assume the OP is saying is the sunlight shining "under" the arch) looks to me just to be a mountain peak rising out of a shadow -- rising high enough for the top of the peak to be in the sunlight.