The more we look at these layers, the more it appears the color differences we've been seeing are primarily texture differences and not intrinsic color differences due to composition. The team is coming around to thinking that this ring is a textural, grain-sized type of difference as opposed to something that is chemically distinct from the other layers and we’re trying to understand that and put in some historical context."

"We're not sure yet if we're going to Gilbert or not," Squyres said. "It hinges on a couple of things. One is whether it's intact or jumbled up blocks. The other is that down into Gilbert the rocks have a lot of sand and berries lying around and we have to convince ourselves that the RAT is capable of clearing away all that crud and getting up to the rock underneath. If not, there's not much point in going down there."