Curiosity finds layers on Mars...

Curiosity finds layers on Mars...  Tiny, thin layers.  I'm no geologist, but to me this says WATER.  All the ways I know that such layers can form involve water with minerals in solution, either invading a crack, or evaporating from a flat surface.  This image was taken with the MAHLI camera, so it is highly magnified.  It was processed with focus-merge, so there is an unusually deep field of focus.  (Many) more here...