Almostly certainly we will see evaporitic sediments without concretions. Aeolian sand generally does not travel very far from its source on earth a few km at most. In this case the sand source is the concretion-rich unit. No sand, ergo, no concretions.<br /><br />The other possibility is that there are concretions there, in which case the win energy must be sufficiently high to sweep the granules away. In this case let's hope there isn't a big blow when Opportunity is about.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em> Arthur Clarke</p> </div>