LROC NAC view of the southern rim of Copernicus crater. Downslope direction is to the upper left and the fragmented material demarcates the rough edge of the crater rim. The surface texture is still sharp and crisp indicating a relatively young age -- note the boulder tracks. LROC NAC image M129418341L, image width is 470 eters (1541 feet).

Copernicus crater played a key role as pioneering lunar geologists Gene Shoemaker and Robert Hackman unraveled the basic stratigraphy of the Moon fifty years ago. Stratigraphy is the science of determining relative ages of geologic materials by observing overlapping relationships between different geologic units. What is a unit? In the case of the Moon, the most basic geologic units include crater ejecta, mare basalt, volcanic ash, and the ancient highlands crust. Dr. Shoemaker and his colleagues noted that rays from different craters exhibited a range of albedos from very bright (Aristarchus crater) to barely visible (Copernicus crater). They correctly inferred that rays fade with time, as they are sand blasted by micrometeorite impacts and exposed to the relentless effects of the solar wind, processes often referred to as "space weathering."� By tracing the path of rays, the relative ages of many units can be easily determined.

NASA's Goddard Space Flight Center built and manages the mission for the Exploration Systems Mission Directorate at NASA Headquarters in Washington. The Lunar Reconnaissance Orbiter Camera was designed to acquire data for landing site certification and to conduct polar illumination studies and global mapping. Operated by Arizona State University, LROC consists of a pair of narrow-angle cameras (NAC) and a single wide-angle camera (WAC). The mission is expected to return over 70 terabytes of image data.