English: Interpretations of cross-lamination patterns presented as clues to this martian rock's (nicknamed "Last Chance") origin under flowing water are marked on images taken by the microscopic imager on NASA's Opportunity rover. The microscopic view is a mosaic of some of the 152 microscopic imager frames of Last Chance that Opportunity took on sols 39 and 40 (March 3 and 4, 2004). This view shows cross-lamination expressed by lines that trend downward from left to right, traced with black lines in the interpretive overlay. These cross-lamination lines are consistent with dipping planes that would have formed surfaces on the down-current side of migrating ripples. Interpretive blue lines indicate boundaries between possible sets of cross-laminae.