"Decorrelation Stretch": layers inside Endurance (stretched colors) - Sol 143

Caption NASA originale:"This PanCam image from Opportunity has been processed using a technique known as "Decorrelation Stretch" (DS) to exaggerate the colors. The area in the image includes 3 holes created inside Endurance Crater by Opportunity's RAT between Sol 143 and Sol 148 (June 18 and June 23, 2004). Because color variations are so subtle in the pictured area, stretched images are useful for discriminating color differences that can alert scientists to compositional and textural variations. For example: without the exaggeration, no color difference would be discernable among the tailings left behind after the grinding of these holes, but in this stretched image, the tailings around 'London' (top) appear more red than those of the other holes (Virginia', middle, and 'Cobble Hill,' bottom). Scientists believe that is because the RAT sliced through 2 "blueberries" or spherules (visible on the upper left and upper right sides of the circle). When the blades break up these spherules, composed of mostly gray hematite, the result is a bright red powder. In this image, you can see the rock layers that made the team want to grind holes in each identified layer. The top layer is yellowish red, the middle is yellowish green and the lower layer is green. Another advantage to viewing this stretched image is the clear detail of the distribution of the rock abrasion tool tailings (heading down-slope) and the differences in rock texture".