AS17-2007(M)

Figure 148

 Original source of NASA image
  Click here for lunar chart showing farside location

This pair of overlapping medium-sized craters illustrates some of the criteria used to determine relative ages. Material ejected from the larger polygonal crater on the left partially fills the smaller crater on the right; thus, the crater on the left is younger. Furthermore, the wall of the large crater is complete, whereas the west wall of the smaller crater is absent, obviously having been destroyed by the larger crater. Even if the two craters did not overlap, the sharp rim, terraced walls, and prominent central peak of the larger crater clearly identify it as the younger of the two. The frames used in the stereogram were selected to show exaggerated relief, a technique very helpful to photointerpreters in determining shapes and relative elevations of surface features. The two craters are located in the rugged terrain of the far-side highlands approximately 250 km north of the prominent crater Tsiolkovsky. The photograph below is an oblique view of the same pair of craters. It is included, not because it is a more dramatic view, but because it shows from another perspective that one crater clearly is superposed on the other.    -M.C.M.