AS17-145-22163 - High resolution version shows the rock is illuminated, likely by the reflective spacesuit.
Actually, that makes a lot of sense.
Firstly, the lens flares top left are a tell-tale for the approximate position of the sun. The white spacesuit will reflect directly down at about the correct range of angles to illuminate the shadow sides of those nearby rocks
Second, and perhaps, most important of all, notice how the nearest rock has the greatest level of shadow-side illumination, and it falls off for the more distant rocks? That's the inverse square law in action; the fall in intensity of the illumination is inversely proportional to the square of the distance from the source. That the drop off is so dramatic means that the source must be close to the nearest rock, for example, the space suit or perhaps the LRV. If the source of the illumination was some distant bright floodlight as HBs erroneously claim, then those shadow faces would be, relatively speaking, more equi-distant from the source, and would therefore, show roughly equal illumination.