To answer the first question, we need to put ourselves in the shoes of American scientists in the late 1950s and early 1960s. This was a time when American science was, for better or for worse, inextricably linked to American Cold War policy. Although the age of Joseph McCarthy’s communist witch hunts had ended, scientists still vividly remembered when atomic bomb developer Robert Oppenheimer was publicly flogged for renouncing his pioneering work and taking a position considered antithetical to U.S. national security—opposing the creation of the hydrogen (thermonuclear) bomb, the A-bomb's exponentially more powerful and destructive successor.
But it wasn’t just fear that inspired physicists, chemists, biologists, astrophysicists and others to join university laboratories, private industries or government institutions working on aerospace and defense research. Many of these scientists were patriots. Some were WWII refugees who had seen tyranny firsthand—and barely escaped it. They, too, believed in what they were doing. The Cold War was a fight to the death—or at least for the future of the free world. These men and women had a skill set that was integral to national, and potentially global, security.
Still, it seems as if bombing the moon just for the public-relations win would stretch the limits of what even the most patriotic scientists would willingly accept.
Some justified it as a scientific breakthrough.
Whether these were serious considerations, or just ways to justify their actions, many involved in Project A119 cited the potential for real and important scientific discovery that could come out of detonating a nuclear weapon on the surface of the moon. These were exciting times, with the potential to explore new frontiers of science. Carl Sagan, the man who would dedicate his life to searching for evidence of life on other worlds, thought this could be a great way to try and identify the presence of microbes or organic molecules on the moon. (This is when we still thought there might be something up there besides dust.)
Others envisioned experiments centered on lunar chemistry, or the thermal conductivity of the lunar surface. Reiffel’s team also wondered if the nuclear blast would produce enough seismic activity to evaluate the makeup of the moon’s immediate subsurface structure. According to Reiffel, “A central theme, which runs through many of the projected experimental situations, envisions placing of a maximum of three identical instrument packages at arbitrary locations on the visible face of the moon prior to any possible nuclear detonation. These instrument packages would be equipped to make a variety of measurements.”
Would this work? Not all the specific technical details of early American ballistic missile technology are clear (some things are still classified), but during an interview Reiffel gave later in life, he insisted we had the capability to hit a target on the moon with an accuracy of within two miles. That’s pretty good, given that the moon is nearly 240,000 miles from Earth.
So that leaves us with the burning question: How insanely cool would the mushroom cloud on the moon look? Ideally, the bomb would be detonated on the edge (known as the terminator) of the dark side of the Moon, so the sun’s light would silhouette the trademark mushroom cloud from behind. It would be totally rad.
Problem was, that wouldn’t happen.
The optics wouldn’t be as dramatic as they initially hoped.
Mushroom clouds from a nuclear explosion are caused by the movement of dust and debris kicked up in a dense atmosphere. The moon, however, is essentially a vacuum. It has some gases hanging around on its surface, but it really doesn’t have an atmosphere like Earth’s. Without the weight of a dense atmosphere, there would be no resistance to the expansion of the nuclear-produced dust and debris. They would just keep on going and going, instead of curling back to the surface. No big plume, no sound or shock wave, no push-down from the air pressure—and no mushroom cloud. Just a lot of dust.
This doesn’t mean there wouldn’t be a hell of a show. People on earth would see a visible flash from the detonation. And maybe the sun would shine through the dust and debris in such a way as to give the world a pretty view. But it really wouldn’t be the same.