It has been suggested that these glassy looking tubes are hollow. I don't think they are transportation tubes, but rather a conduit possible for water. These tubes show up on many pictures, not always as well pronounced as in the following picture. The tubes are clearly ribbed, what might have to do with structural strength. Their width varies a lot, what makes their function as transportation tubes unlikely. Also take into account that the exposed tubes are covered by dust and sand that is blowing around. Only the sections that are high up are showing a bright reflection of the sunlight. The tubes seem to be form a network that lies just under the surface. Sporadically, erosion of the thin layers above the tubes have been eroded, exposing their existence.