I will admit that, even though I still don't believe that theory is the best candidate. But here, it looks like one good possibility is that these are concretions that just didn't form as well as the perfect ones of Meridiana. What do you want, perfect spherical concretions everywhere? This was one of my biggest argument against the Meridiana spheres being concretions; they are too perfect over a wide area (everywhere in Meridiana, so far), where are the poorly formed ones that should be more common for concretions (but maybe not for precipitates). Well, here we may just be seeing some less spherical, less solid concretions.