What do you think made the bright features in the picture below? Was it a deep layer of rock underneath sand that was swept away by wind? Or maybe it was salt left over from the drying of an ancient lake? Or perhaps even ash left over by an ancient volcano.  One of the answers is correct, and not the one I was hoping for. I wish it was from an ancient lakebed, oh what the salt deposits could teach us.  But alas, it is only volcanic ash.  So as true scientists, we follow what the data tells us, and learn...