In the red box above is a curving corrugated sheet found on Mars. Image cropped and enlarged from www.jpl.nasa.gov/spaceimages/details.php?id=PIA19818 (Note: Click the blue words “Download the full resolution annotated TIFF file”. Then look in the lower left corner of the downloaded image.) Added on Oct. 8, 2015: Reasons why it is not a rock
1. Red line 1 goes to a flat surface while red line 2 goes to a corrugated surface.
2. Red lines 3 and 4 go to the upward curving portions of the object.