David A. Kring
In the late 1960’s an experiment called Mare Exemplum was conducted to simulate impact-generated erosion and sedimentation processes that occur on the lunar surface. A series of projectiles of different diameters were shot or dropped into an analogue of the lunar surface. Six different size projectiles hit a target of quartz sand, such that ten craters were created in one size class for every one crater in the next larger size class. The sequence was photographed and those photographs were then strung together into a film to illustrate the evolution from a smooth, flat surface to one saturated with craters. The sequence also demonstrates how new craters are constantly obliterating older craters; thus, a cratered surface seen at any particular time (like today) is only a small measure of the number of impacts that have occurred. Relatively small diameter projectiles were used in the experiment, so the sequence represents the types of cratering events that affect the regolith over a 1 to 10 year period. However, it is easy to visualize the same cratering processes occurring at much larger scales.
The film was prepared at the NASA Ames Research Center, Moffett Field, California, as part of a cooperative program of impact-cratering research being conducted with the U.S. Geological Survey. The research scientists in charge of the experiment were Donald E. Gault, William L. Quaide, Verne R. Oberbeck, and Henry J. Moore. Technical support was provided by Friedrich Hörz, John A. Wedekind, Lawrence J. Robello, Roger V. Krause, and Dino G. Penseggi.
This film was originally produced in a 16 mm format. A copy of the film was kindly provided by Friedrich Hörz and digitized by the LPI-JSC Center for Lunar Science and Exploration in 2011 for presentation here. The film is narrated, so you should hear a voice about 53 seconds into the 5:46 minute film.