This magnified view from NASA's Mars Exploration Rover Opportunity of aportion of a martian rock called "Upper Dells" shows fine layers (laminae)that are truncated, discordant and at angles to each other. In Figure 1, interpretiveblack lines trace cross-lamination that indicates the sediments thatformed the rock were laid down in flowing water; the interpretive blue linespoint to boundaries between possible sets of cross-laminae.
This rock, like another called "Last Chance," (see PIA05482) preserves evidence for trough cross-lamination, likely produced when flowing water shaped sinuous ripples in underwater sediment and pushed the ripples to migrate in one direction. The direction of the ancient flow would have been toward or away from the viewer.
Several frames taken with Opportunity's microscopic imager during therover's 41st sol on Mars (March 5, 2004) are stitched together to makethis mosaic view. Eight spherules can be seen embedded in the rock, andone larger pebble sits on the present-day surface of the rock.