|This HiRISE image shows geologic "contacts", or boundaries, between light-toned and dark-toned material in Meridiani Planum, near the equator of Mars. Merdiani Planum is where the Mars Exploration Rover Opportunity is located, although this image covers an area that is more than 600 km to the east of the Opportunity site. The central portion of the image shows very smooth, dark plains that are typical of much of the Meridiani region. These plains are flanked by more rugged lighter-toned materials. The light-toned materials have been eroded to form pits, buttes and mesas. Based on the lengths of the shadows that they cast, some of the buttes and mesas are up to about 30 meters (~100 feet) tall. The light-toned material shows distinctive layering, suggesting that it may be composed of sedimentary rock. Scattered across the scene, especially in the light-toned materials where they are prominent in low spots and around some of the larger buttes and mesas, are dunes and other similar landforms created by martian winds. The image scale is 54 cm/pixel (with 2 x 2 binning) so objects ~162 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel and north is up. The image was taken at a local Mars time of 3:28 PM and the scene is illuminated from the west with a solar incidence angle of 55.3 degrees, thus the sun was about 34.7 degrees above the horizon.