The astrogeologists with the U.S. Geological Survey were instrumental in planning the Apollo moonwalks and preparing NASA's astronauts to collect samples and observations while on the lunar surface. Among other noteworthy endeavors, they used explosives to create crater-filled replicas of the Moon’s surface to use in training simulations. To do that, they first tested different amounts of explosives to figure out how to make craters of different sizes, allowing them to closely match the terrain of the Moon