These images taken by the Mars Reconnaissance Orbiter document the appearance of a new cluster of impact craters on Mars. The upper-right image (May 2011) shows a dark patch at the center that is not present in the upper-left image, taken in August 2010. The scale bar on each of these two images is 2.5 kilometers (1.6 miles). Impacts produce a dark-looking blast zone where the dust is disturbed. Researchers investigated the new dark spot with the UA's HiRISE camera, obtaining the lower image showing a cluster of small, fresh craters. The scale bar on this image is 100 meters (328 feet).