See my earlier comment about "bathtub rings"
They are, as I see it, palaeo-ground surfaces in an aeolian-dominated environment where liquid seepage to the surface has developed a sulphate crust. In the earlier panaorama you can track the ring(s) round the whole visible half of the crater. SOme places there is one band, then it splits to two.
When the NASA boys finally catch up on the science here, there'll be some great stories, and some interesting changes to the er\arlier ideas about lakes and seas, methinks. You have seen the giant crossbeds in the cliffs?