NASA knew full well that the Apollo lunar landing missions were risky, and it took steps to minimize the chances of losing astronauts in space.
Redundancies were built into the spacecraft, and astronauts and technicians alike spent hours simulating missions. Mission planners also used simulations to anticipate as many aspects of a lunar mission as possible, going so far, in 1967, as recreating the moon in northern Arizona.
ANALYSIS: Apollo 18: The Lost Apollo Missions
The Arizonian landscaping was part of the Astrogeology Research Program, a joint undertaking between NASA and the United States Geological Survey (USGS). Beginning in 1963, the idea was to give Apollo astronauts as realistic a training ground as possible for their eventual EVAs on the lunar surface.
The program's main site was a place called Cinder Field, an area where basaltic cinders covered the natural clay landscape following the Sunset Volcanic Crater's eruption around 1064. To make it more moon-like, NASA added craters to the site with dynamite. To make each crater, a site was excavated and filled with a mixture of dynamite and ammonium nitrates. After some test explosions, a necessary step to calibrate how much power was needed to make a crater of a certain size, the real blasting began.