LROC NAC frame closeup of crater wall and terrace in Bürg crater (45.0°N, 28.2°E). The outer rim of the crater is along the right side of the frame. Image width is 1.62 km [NASA/GSFC/Arizona State University]
Bürg is a 40-km diameter, Copernican-aged, complex crater located within Lacus Mortis (the Lake of Death) on the nearside of the Moon. Complex craters, like this one, have terraced walls and a central peak (not shown here). The rim of the crater is along the right side and the walls slope down towards the left of the image. The terrace shown is ~1 km wide and is pockmarked with smaller craters. Terraces form as sections of the crater wall slump downward after the impact. Note that there are very few impact craters on the wall of the crater. Usually fewer craters indicate a surface is younger, however in this case its simply that material slides down the crater wall's steep slopes erasing craters. See Chapter 3 in the Geologic History of the Moon by Don Wilhelms for more information about lunar impact craters.
LROC is capturing high-resolution images of the walls and floors of impact craters on the Moon. These images will provide detailed information on the processes that form complex craters. One of the mission objectives for LROC is to estimate current impact rates and hazards in preparation for NASA's return to the lunar surface by 2020. Browse the whole NAC image!